COLLEGE  QF  AGRICULTURE 

1  ECOHORSICS 

UNIVERSITY  OF  CALIFORNIA 
BERKELEY,  CALIFORNIA 


Absor ptioki  Spectra. 


Oxy  haemoglobin. 


Haemoglobin. 


Carboxy- 

haemoglobin. 


Neutral  Met- 

haemoglobin. 


Alkatine  Met- 
haemoglobin. 


Alkali 
Haematin. 


Absorption  Specif. 

PLATE  w.^-, ::"  V'/j 


Reduced  Alkali 
Haematin  or 
Haemochromogen. 


Acid  Haematin  in 
ethereal  solution. 


14 


Acid  Haemato- 
porphyrin. 


Alkaline 

Haematopor- 
phyrln. 


Urobilin  or  Hydro- 
bilirubin  In  acid 
solution. 


Urobilin  or  Hydro- 
bilirubin  -in  alkaline 
solution  after  the 
addition  of  zinc 
chloride  solution. 


Bill  cyan  in  or 
Cholecyanin  in 
alkaline  solution. 


PRACTICAL 

PHYSIOLOGICAL  CHEMISTRY 


A  BOOK  DESIGNED  FOR  USE  IN  COURSES  IN  PRACTICAL 

PHYSIOLOGICAL  CHEMISTRY  IN  SCHOOLS 

OF  MEDICINE  AND  OF  SCIENCE 


BY  v 

PHILIP  B.  HAWK,  M.  S.,  Ph.  D. 

PROFESSOR  OF  PHYSIOLOGICAL  CHEMISTRY  AND  TOXICOLOGY  IN  THE 
JEFFERSON  MEDICAL  COLLEGE  OF  PHILADELPHIA 


SEVENTH  EDITION,  REVISED 


WITH  TWO  FULL-PAGE  PLATES  OF  ABSORPTION  SPECTRA  IN  COLORS 

FOUR  ADDITIONAL  FULL-PAGE  COLOR  PLATES  AND  ONE 

HUNDRED  AND  NINETY-TWO  FIGURES  OF  WHICH 

TWELVE  ARE  IN  COLORS 


PHILADELPHIA 

P.  BLAKISTON'S  SON  &  CO. 

1012  WALNUT  STREET 


BIOLOGY 


COPYRIGHT,  1921,  BY  P.  BLAKISTON'S  SON  &  ^T!o. 


THE     M  A.  F  L  K     F  K  E  S  S     Y  O  H  K     FA 


THESE  PAGES  ARE 

AFFECTIONATELY  DEDICATED 

TO 

MY  PARENTS 


V 


BIOLOGY 

LIBRARY 


PREFACE  TO  THE  SEVENTH  EDITION 


After  a  lapse  of  three  years  the  entire  volume  has  been  thoroughly 
revised,  in  an  attempt  to  bring  it  strictly  up  to  date.  To  obviate  the 
necessity  of  further  enlarging  the  book,  many  methods  and  tests 
which  the  author  believes  to  have  outlived  their  usefulness  have  been 
omitted,  in  order  to  afford  space  for  more  modern  procedures.  Inas- 
much as  "blood  counting"  is  not  a  part  of  the  greater  number  of  courses 
in  physiological  chemistry,  all  discussion  of  this  subject  has  been  elimi- 
nated. Among  other  changes  in  the  carefully  revised  chapter  on 
''Blood  Analysis"  the  excellent  analytical  system  of  Folin  and  Wu  has 
been  included  in  its  entirety.  No  course  is  complete  without  a  con- 
sideration of  these  thoroughly  up-to-date  methods.  The  chapter  on 
"Acidosis"  has  been  expanded  to  include  a  brief  consideration  of 
respiration  and  is  now  called  " Respiration  and  Acidosis."  The  chapter 
on  "Quantitative  Analysis  of  Urine"  is  introduced  by  a  discussion  of 
Normal  and  Standard  Solutions  and  their  Method  of  Preparation. 
Procedures  similar  to  those  given  here  in  concise  form  are  used  in  the 
best  medical  schools  in  the  country  as  an  introduction  to  their  practical 
courses  in  physiological  chemistry.  In  line  with  the  increasing  know- 
ledge and  importance  of  Vitamines,  considerable  space  has  been  given 
to  this  subject  in  the  section  on  Metabolism.  .  In  this  connection  sug- 
gestions are  made  as  to  suitable  ways  of  demonstrating  various  "diet- 
ary deficiencies."  The  proper  way  to  cage  and  care  for  animals  used 
in  such  experiments  is  also  discussed. 

As  usual,  the  author  is  under  great  obligations  to  his  confrere,  Dr. 
Olaf  Bergeim,  for  invaluable  assistance  in  all  matters  pertaining  to 
revision  and  proof.  Dr.  Clarence  A.  Smith  has  also  rendered  valuable 
aid  in  connection  with  this  new  edition.  The  author  also  wishes  to 
thank  Miss  Katherine  Loewinson,  Dr.  Raymond  J.  Miller,  and  Mr. 
Bernard  L.  Oser  for  assistance. 

It  is  a  pleasure  to  acknowledge  the  many  courtesies  extended  to  the 
author  by  the  publishers  of  this  volume. 


Vll 


CONTENTS 

CHAPTER  I 

PAGE 

.ENZYMES  AND  THEIR  ACTION i 

CHAPTER  II 
CARBOHYDRATES   *9 

CHAPTER  III 
v  SALIVARY  DIGESTION 53 

CHAPTER  IV 
PROTEINS:  THEIR  DECOMPOSITION  AND  SYNTHESIS  ...> 62 

CHAPTER  V 
PROTEINS:  THEIR  CLASSIFICATION  AND  PROPERTIES 92 

CHAPTER  VI 
NUCLEIC  ACIDS  AND  NUCLEOPROTEINS 122 

CHAPTER  VII 

GASTRIC  DIGESTION 137 

CHAPTER  VIII 
GASTRIC  ANALYSIS 150 

CHAPTER  DC 
FATS 179 

CHAPTER  X 

•  •  :  .                                                     \ 
PANCREATIC  DIGESTION .  188 

CHAPTER  XI 

~s  INTESTINAL  DIGESTION 198 

^* 

CHAPTER  XII 

\   BILE    .   .  ..   . 205 

CHAPTER  XIH 
PUTREFACTION  PRODUCTS 215 

CHAPTER  XIV 

FECES , 224 

ix 


X  CONTENTS 

CHAPTER  XV 

PAGE 
BLOOD  AND  LYMPH 248 

CHAPTER  XVI 
BLOOD  ANALYSIS 273 

CHAPTER  XVII 
RESPIRATION  AND  ACIDOSIS 304 

CHAPTER  XVIII 
MILK 329 

CHAPTER  XIX 

EPITHELIAL  AND  CONNECTIVE  TISSUES:  TEETH 348 

CHAPTER  XX 

MUSCULAR  TISSUE 357 

CHAPTER  XXI 
NERVOUS  TISSUE 370 

CHAPTER  XXII 
URINE:  GENERAL  CHARACTERISTICS  OP  NORMAL  AND  PATHOLOGICAL  URINE    .    .    .376 

CHAPTER  XXIII 
URINE:  PHYSIOLOGICAL  CONSTITUENTS' .V.:'.   .   .  v  .   .   .   .   .   ...  386 

CHAPTER  XXIV 

URLNE:  PATHOLOGICAL  CONSTITUENTS 430 

CHAPTER  XXV 
URINE:  ORGANIZED  AND  UNORGANIZED  SEDIMENTS 474 

CHAPTER  XXVI 
URINE:  CALCULI "•'.,  «,..v 492 

CHAPTER  XXVII 

URINE:  QUANTITATIVE  ANALYSIS    .   .-.  ,  .'-.-',  .  .   . 496 

CHAPTER  XXVin 
METABOLISM .   .._;,,  .  .  *  . 579 

REAGENTS  AND  SOLUTIONS. 627 

INDEX .* .   . 649 


LIST  OF  ILLUSTRATIONS 


PLATE 

I.    Absorption  Spectra  1  Frontispiece 

II.    Absorption  Spectra  J 

III.  Osazones Opposite  page  22 

IV.  Normal  Erythrocytes  and  Leucocytes  . Opposite  page  252 

V.  Uric  Acid  Crystals Opposite  page  397 

VI.  Ammonium  Urate Opposite  page  479 

FIGURE  PAGE 

- 

1.  Apparatus  for  Quantitative  Determination  of  Catalase 17 

2.  Dialyzing  Apparatus  for  Students'  Use 24 

3.  Apparatus  for  Alcoholic  Fermentation  Experiment .  30 

4.  lodoform v 3° 

5.  Einhorn  Saccharometer 30 

6.  One  Form  of  Laurent  Polariscope 31 

7.  Diagrammatic  Representation  of  the  Course  of  the  Light  through  the  Laurent 

Polariscope 33 

8.  Polariscope  (Schmidt  and  Hansch  Model) 33 

9.  Potato  Starch .    .  44 

10.  Bean  Starch 44 

11.  Arrowroot  Starch 44 

12.  Rye  Starch . 44 

13.  Barley  Starch '.    .    .  44 

14.  Oat  Starch 44 

15.  Buckwheat  Starch 44 

16.  Maize  Starch 44 

17.  Rice  Starch 44 

18.  Pea  Starch 44 

19.  Wheat  Starch 44 

20.  Microscopical  Constituents  of  Saliva 57 

21.  Glycocoll  Ester  Hydrochloride 71 

22.  Serine 72 

23.  Phenylalanine  . 73 

24.  Fischer  Apparatus 74 

25.  Tyrosine.  ......  X   .   ^ 75 

26.  Cystine ,   .   ..... 75 

27.  Histidine  Bichloride .  77 

28.  Leucine 79 

29.  Lysine  Picrate 80 

30.  Aspartic  Acid   .   ^  -. 80 

31.  Glutamic  Acid.    .   .  .   .*, "..- 82 

32.  Levo-a-Proline 83 

33.  Copper  Salt  of  Proline 83 

34.  Van  Slyke  Amino  Nitrogen  Apparatus 87 

35.  Section  of  Van  Slyke  Apparatus 87 

36.  Coagulation  Temperature  Apparatus 105 

37.  Edestin 108 

38.  Excelsin,  the  Protein  of  the  Brazil  Nut 109 


Xll  ILLUSTRATIONS 

FIGURE  PAGE 

39.  Guanine  Chloride 134 

40.  Hypoxanthine  Chloride 135 

41.  Curves  Showing  Stimulatory  Power  of  Water 144 

42.  Curves  Showing  Stimulatory  Power  of  Water 144 

43.  Curves  Showing  Stimulatory  Power  of  Beef  Extract 147 

44.  Curves  Showing  Psychial  Stimulation  of  Gastric  Secretion 148 

45.  Normal  and  Pathological  Curves  after  an  Ewald  Meal 150 

46.  Rehfuss  Stomach  Tube 151 

47.  Bergeim  Intragastric  Conductance  Apparatus 152 

48.  Curves  Showing  Relationship  of  Conductance  of  Acidities 152 

49.  Influence  of  Acid  Introduced  into  the  Normal  Human  Stomach 153 

50.  Hydrogen  Ion  Concentration  Chart 160 

51.  Acidity  Curves  of  Normal  Human  Stomach 166 

52.  Acidity  Curves  from  a  Case  of  Hyperacidity 167 

53.  Acidity  and  Protein  Curves  in  Gastric  Carcinoma 167 

54.  Tyotal  Acidity  and  Protein  Curves  in  Benign  Achylia 168 

55.  Microscopical  Constituents  of  the  Gastric  Contents 175 

56.  Beef  Fat 179 

57.  Mutton  Fat 182 

58.  Pork  Fat 184 

59.  Palmitic  Acid 185 

60.  Melting-point  Apparatus 186 

61.  Bile  Salts 208 

62.  Bilirubin  (Hematoidin) 208 

63.  Cholesterol    ....... ..    . 213 

64.  Taurine 214 

65.  Glycocoll 214 

66.  Ammonium  Chloride 219 

67.  Hematoidin  Crystals  from  Acholic  Stools 225 

68.  Charcot-Leyden  Crystals 228 

69.  Boas'  Sieve ' .    .  232 

70-75.  Microscopical  Constituents  of  Feces 233-234 

76.  Oxyhemoglobin  Crystals  from  Blood  of  the  Guinea-pig 254 

77.  Oxyhemoglobin  Crystals  from  Blood  of  the  Rat 254 

78.  Oxyhemoglobin  Crystals  from  Blood  of  the  Horse    .    ... 255 

79.  Oxyhemoglobin  Crystals  from  Blood  of  the  Squirrel.    . .  ...  .•  v  •'  •  "^ -.: .    .    .    .  255 

80.  Oxyhemoglobin  Crystals  from  Blood  of  the  Dog  ;•:... 256 

81.  Oxyhemoglobin  Crystals  from  Blood  of  the  Cat 256 

82.  Oxyhemoglobin  Crystals  from  Blood  of  the  Necturus 257 

83.  Effect  of  Water  on  Erythrocytes 264 

84.  Hemin  Crystals  from  Human  Blood 268 

85.  Hemin  Crystals  from  Sheep  Blood ••-.    .  '.   »  -' 268 

86.  Sodium  Chloride .-.   ,    .    .    .-r  7  .    .    .  •-. ... 269 

87.  Diluting  Pipette  .    .    .    .;...>,... .    .  276 

88.  Apparatus  for  Distillation  of  Ammonia  from  Urea .'»,....  279 

89.  Folin-Wu  Sugar  Tube ......  ~.    ....  283 

90.  Aspiration  Apparatus  for  Urea  Determination  ../,.......-••  286 

91.  Bang  Reduction  Flask.   ....;.    . .-,  '.*   .   .'  .   .  v  .   4 289 

92.  Sugar  Tolerance  Curves  .......   .   .    .    ,  .   .   ;  v  .*..-'.    .    .   .    .    .    .    .  290 

93.  Extraction  Apparatus  for  Cholesterol  Determination   .    .    ...    .    .    .\.    ;   .    .  292 

94.  Bloor's  Nephelometer 295 

95.  Nephelometer  in  Position,  Showing  Relation  to  Source  of  Light 296 

96.  Kober's  Nephelometer — Colorimeter .  297 

97.  Direct-vision  Spectroscope .1  •.•;..  300 


ILLUSTRATIONS  Xlll 

FIGURE  PAGE 

98.  Angular-vision  Spectroscope  Arranged  for  Absorption  Analysis      300 

99.  Diagram  of  Angular- vision  Spectroscope 301 

100   Van  Slyke  Carbon  Dioxide  Apparatus 312 

101.  Tube  Used  in  Collecting  Blood 312 

102.  Separatory  Funnel  used  in  Saturating  Blood  Plasma  with  Carbon  Dioxide  .    .    .313 

103.  Fridericia  Apparatus 320 

104.  Normal  Milk  and  Colostrum 331 

105.  Curd  of  Human  Milk 332 

106.  Curd  of  Human  Milk 332 

107.  Curd  of  Cows' Milk .    . 332 

108.  Curd  of  Cows'  Milk .    .  33.2 

109.  Lactose 335 

no.  Calcium  Phosphate 340 

in.  Centrifuge  Tube  Used  in  Babcock  Fat  Method 342 

112.  CrolPs  Fat  Apparatus 343 

113.  Soxhlet  Apparatus 344 

114.  Feser's  Lactoscope 344 

115.  Creatine * ...,....., 360 

116.  Xanthine : 362 

117.  Hypoxanthine  Silver  Nitrate 369 

1 1 8.  Xanthine  Silver  Nitrate -.    .    .    .   369 

119.  Deposit  in  Ammoniacal  Fermentation 379 

1 20.  Deposit  in  Acid  Fermentation 380 

121.  Urinometer  and  Cylinder * 381 

122.  Beckmann-Heidenhain  Freezing-point  Apparatus 382 

123.  Urea Y 389 

124.  Urea  Nitrate 391 

125.  Melting-point  Tubes  Fastened  to  Bulb  of  Thermometer 392 

126.  Urea  Oxalate 393 

127.  Pure  Uric  Acid 397 

128.  Creatinine 399 

129.  Creatinine-Zinc  Chloride ';.,."> 402 

130.  Hippuric  Acid 406 

131.  Allantoin  from  Cat's  Urine 409 

132.  Benzoic  Acid 413 

133.  Calcium  Sulphate 423 

134.  "  Triple  Phosphate  " 426 

135.  Albumoscope 440 

136.  Pentosazone 457 

137.  Marsh  Apparatus.- 463 

138.  The  Purdy  Electric  Centrifuge 474 

139.  Sediment  Tube  for  the  Purdy  Electric  Centrifuge 474 

140.  Calcium  Oxalate 476 

141.  Calcium  Carbonate 476 

142.  Various  Forms  of  Uric  Acid 478 

143.  Acid  Sodium  Urate 479 

144.  Cystine 479 

145.  Crystals  of  Impure  Leucine 480 

146.  Epithelium  from  Different  Areas  of  the  Urinary  Tract 483 

147.  Pus  Corpuscles 484 

148.  Hyaline  Casts 485 

149.  Granular  Casts 486 

150.  Granular  Casts 487 

151.  Epithelial  Casts .    . .   487 


xiv  ILLUSTRATIONS 

FIGURE  PAG  E 

152.  Blood,  Pus,  Hyaline  and  Epithelial  Casts 487 

153.  Fatty  Casts ...  488 

154.  Fatty  and  Waxy  Casts . 488 

155.  Cylindroids 489 

156.  Crenated  Erythrocytes ....   490 

157.  Human  Spermatozoa 491 

158.  Folin  Fume  Absorber 505 

159.  Folin  Wright  Distillation  Apparatus 507 

160.  Duboscq  Colorimeter  ......' 508 

161.  Bock  Benedict  Colorimeter 509 

162.  Myers  Test-tube  Colorimeter    .    .    .    .  ^ 510 

163.  164.  Forms  of  Apparatus  used  in  Methods  of  Folin  and  Associates  for  Determi- 
nation of  Total  Nitrogen,  Urea  and  Ammonia 511 

165.  Bock    and    Benedict    Apparatus 512 

166.  Van  Slyke  and  Cullen  Apparatus 515 

167.  Folin's  Ammonia  Apparatus 519 

168.  Folin  Improved  Absorption  Tube 520 

169.  Esbach's  Albuminometer 551 

170.  Growth  Curve  of  Albino  Rat 583 

171.  Growth  Curve  of  Albino  Rat  Showing  Importance  of  Water-soluble  "  B  "    .    .    .584 

172.  Rat  Fed  a  Diet  Containing  Sufficient  Water-soluble  "B" 585 

173.  Rat  Fed  a  Diet  Deficient  in  Water-soluble  "B" 585 

174.  Growth  Curve  of  Albino  Rat  Showing  Importance  of  Water-soluble  "B"  .    .    .  586 

175.  Rat  Fed  a  Diet  Deficient  in  Fat-soluble  A  (Left)  and  Rat  Fed  an  Adequate  Diet 
(Right) ' 587 

176.  The  Fat-soluble  Vitamine  and  Growth 587 

177.  Guinea  Pig  with  Scurvy.     Showing  "  Scurvy  Position " .    :    .    .  588 

178.  Guinea  Pig  with  Scurvy,  Showing  "Face  Ache  Position" 589 

179.  Rat  Cage  for  Nutrition  Experiments,  Showing  Individual  Parts 590 

1 80.  Rat  Cage  for  Nutrition  Experiments,  Assembled 590 

181.  Rat  Cage  for  Stock  Animals      .    ....-..„  V  .  7.    .    . 591 

182.  Breeding  Cage   .    .    .    .    .    ...    .    .    .    .    .    .    .-.    .    ..-•,. 591 

183.  Curve  Showing  Influence  of  a  Deficiency  of  Cystine  in  the  Diet 592 

184.  Curve  Showing  Influence  of  a  Deficiency  of  Lysine  in  the  Diet  ,'  ,    ,  '«,  ....  593 

185.  Rat  Receiving  Wheat  Protein  and  Gelatine.     The  Diet  Contained  Sufficient 
Lysine ;...., .,..-":..',    .  594 

1 86.  Rat  Receiving  Wheat  Protein  Only.     This  Diet  was  Deficient  in  Lysine      ....  595 

187.  Growth  Curve  of  Rat  With  and  Without  Calcium  and  Phosphorus  in  the  Diet   .    .  597 

188.  Blood  Sugar  as  Influenced  by  Diet  .    .    ,:..'f_.- -v   .    .    .  599 

189.  Blood  Sugar  Curve  of  Diabetic  after  Glucose  Ingestion 600 

190.  Influence  of  Protein  Ingestion  on  Endogenous  Uric  Acid  Output  .......  606 

191.  The  Endogenous  Uric  Acid  Output  during  Fasting  .    ....    .    .    .    .    .    .    .    .  606 

192.  Berthelot-Atwater  Bomb  Colorimeter 617 


PHYSIOLOGICAL  CHEMISTRY 


CHAPTER  I 
ENZYMES  AND  THEIR  ACTION 

According  to  the  old  classification  ferments  were  divided  into  two 
classes,  the  organized  ferments  and  the  unorganized  ferments.  As  organ- 
ized ferments  or  true  ferments  there  were  grouped  such  substances  as 
yeast  and  certain  bacteria  which  were  supposed  to  act  by  virtue  of  vital 
processes,  whereas  the  unorganized  ferments  included  salivary  amylase 
(ptyalin),  gastric  protease  (pepsin),  pancreatic  protease  (trypsin),  etc., 
which  were  described  as  "non-living  unorganized  substances  of  a 
chemical  nature."  Kiihne  designated  this  latter  class  of  substances  as 
enzymes  (kv  ^u/zrj — in  yeast).  This  division  into  organized  ferments 
(true  ferments)  and  unorganized  ferments  (enzymes)  was  generally 
accepted  and  was  practically  unquestioned  until  Buchner  overthrew 
it  in  the  year  1897  by  his  epoch-making  investigations  on  zymase. 
Previous  to  this  time  many  writers  had  expressed  the  opinion  that  the 
action  of  the  ferment  organisms  was  similar  to  that  of  the  unorganized 
ferments  or  enzymes  and  that  therefore  the  activity  of  the  former  Wv  ° 
possibly  due  to  the  production  of  a  substance  in  the  cell,  which  was  in 
nature  similar  to  an  enzyme.  Investigation  after  investigation,  how- 
ever, failed  to  isolate  any  such  principle  from  an  active  cell  and  the 
exponents  of  the  "  vital"  theory  became  strengthened  in  their  belief  that 
certain  fermentative  processes  brought  about  by  living  cells  could  not 
occur  apart  from  the  biological  activity  of  such  cells.  However,  as 
early  as  1858,  Traube  has  enunciated,  in  substance,  the  principles 
which  were  destined  to  be  fundamental  in  our  modern  theory  of  fermen- 
tation. He  expressed  the  belief  that  the  yeast  cell  produced  a  product 
in  its  metabolic  activities  which  had  the  property  of  reacting  with  sugar 
with  the  production  of  carbon  dioxide  and  alcohol,  and  further  that  this 
reaction  between  the  product  of  the  metabolism  of  the  yeast  cell  and  the 
sugar  occurred  without  aid  from  the  original  cell.  It  was  not  until  1897, 
however,  that  this  theory  was  placed  upon  a  firm  experimental  basis. 
This  was  brought  about  through  the  efforts  of  Buchner,  who  succeeded  in 
isolating  from  the  living  yeast  cells  a  substance  (zymase)  which,  when 
freed  from  the  last  trace  of  organized  cellular  material,  was  able  to  bring 


"  2  PHYSIOLOGICAL   CHEMISTRY 

about  the  Metttioalfetineritative  processes  which,  up  to  this  time,  had 
been  deemed  possible  only  in  the  presence  of  the  active,  living  yeast  cell. 

Buchner's  manipulation  of  the  yeast  cells  consisted  in  first  grind- 
ing them  with  sand  and  infusorial  earth,  after  which  the  finely  divided 
material  was  subjected  to  great  pressure  (300  atmospheres)  and  yielded 
a  liquid  which  possessed  the  fermentative  activity  of  the  unchanged 
yeast  cell.1  This  liquid  contained  zymase,  the  principal  enzyme  of 
the  yeast  cell.  Later  the  lactic-acid-  and  acetic-acid-producing  bac- 
teria were  subjected  by  Buchner  to  treatment  similar  to  that  accorded 
the  yeast  cells,  and  the  active  intracellular  enzymes  were  obtained. 
Many  other  instances  are  on  record  in  which  a  soluble,  active  agent  has 
been  isolated  from  ferment  cells,  with  the  result  that  it  is  pretty  well 
established  that  all  the  so-called  organized  ferments  elaborate  sub- 
stances of  this  character. 

Enzymes  act  by  catalysis  and  hence  may  be  termed  catalyzers  or 
catalysts.  A  simple  rough  definition  of  a  catalyst  is  "a  substance 
which  alters  the  velocity  of  a  chemical  reaction  without  undergoing 
any  apparent  physical  or  chemical  change  itself  and  without  becoming 
a  part  of  the  product  formed."  It  is  a  well-known  fact  that  the  veloc- 
ity of  the  greater  number  of  chemical  reactions  may  be  changed 
through  the  presence  of  some  catalyst.  For  example,  take  the  case 
of  hydrogen  peroxide.  It  spontaneously  decomposes  slowly  into  water 
and  oxygen.  In  the  presence  of  colloidal  platinum,2  however,  the  de- 
composition is  much  accelerated  and  ceases  only  when  the  destruction 
of  the  hydrogen  peroxide  is  complete.  Without  multiplying  instances, 
suffice  it  to  say  that  there  is  a  close  analogy  between  inorganic  catalysts 
and  enzymes,  the  main  point  of  difference  between  the  enzymes  and 
most  of  the  inorganic  catalysts  being  that  the  enzymes  are  colloids.  The 
great  majority  of  enzymes  are  hydrolytic  in  character. 

We  may  define  an  enzyme  as  an  organic  catalyst  which  is  elaborated 
by  an  animal  or  vegetable  cell  and  whose  activity  is  entirely  independent 
of  any  of  the  life  processes  of  such  a  cell.  According  to  this  definition 
the  enzyme  zymase  elaborated  by  the  yeast  cell  is  entirely  comparable 
to  the  enzyme  pepsin  elaborated  by  the  cells  of  the  stomach  mucosa. 
One  is  derived  from  a  vegetable  cell,  the  other  from  an  animal  cell,  yet 
the  activity  of  neither  is  dependent  upon  the  integrity  of  the  cell. 

Inasmuch  as  each  of  the  enzymes  has  an  action  which  is  more  orles 
specific  in  character,  and  since  it  is  a  fairly  simple  matter,  ordinarily,  to 
determine  the  character  of  that  action,  the  classification  of  the  enzymes 

*In  later  investigations  the  process  was  improved  by  freezing  the  ground  cells  with 
liquid  air  and  finely  pulverizing  them  before  applying  the  pressure. 

2  Produced  by  the  passage  of  electric  sparks  between  two  platinum  terminals  immersed 
in  distilled  water,  thus  liberating  ultra-microscopic  particles. 


ENZYMES   AND    THEIR   ACTION  3 

is  not  attended  with  very  great  difficulties.  They  are  ordinarily  classi- 
fied according  to  the  nature  of  the  substrate1  or  according  to  the  type 
of  reaction  they  bring  about.  Thus  we  have  various  classes  of  enzymes, 
such  as  amylolytic,2  proteolytic,  lipolytic,  glycolytic,  uricolytic,  autolytic, 
oxidizing,  reducing,  inverting,  protein-coagulating,  deamidizing,  etc.  In 
every  instance  the  class  name  indicates  the  individual  type  of  enzy- 
matic activity  which  the  enzymes  included  in  that  class  are  capable  of 
accomplishing.  For  example,  amylolytic  enzymes  facilitate  the  hydro- 
lysis of  starch  (amylum)  and  related  substances,  lipolytic  enzymes 
facilitate  the  hydrolysis  of  fats  (AITTOS),  whereas  through  the  agency  of 
uricolytic  enzymes  uric  acid  is  broken  down.  There  is  a  tendency, 
at  the  present  time,  to  harmonize  the  nomenclature  of  the  enzymes  by 
the  use  of  the  termination  -ase.  According  to  this  system  of  nomen- 
clature, all  starch-transforming  enzymes,  or  so-called  amylolytic  en- 
zymes, are  called  amylases;  all  fat-splitting  enzymes  are  called  Upases, 
etc.  Thus  ptyalin,  the  amylolytic  enzyme  of  the  saliva,  would  be 
termed  salivary  amylase  in  order  to  distinguish  it  from  pancreatic  amy- 
lase  (amylopsin)  and  vegetable  amylases  (diastase,  etc.).  According 
to  the  same  system,  the  fat-splitting  enzyme  of  the  gastric  juice  would 
be  termed  gastric  lipase  to  differentiate  it  from  pancreatic  lipase  (steap- 
sin) ,  the  fat-splitting  enzyme  of  the  pancreatic  juice. 

Defensive  (protective)  enzymes  are  those  believed  to  be  manufac- 
tured by  certain  cells  (perhaps  the  leucocytes)  and  passed  into  the 
circulating  blood  in  order  to  digest  any  foreign  material  of  endogenous 
or  exogenous  origin  that  may  have  found  its  way  into  the  circulation. 
The  most  important  defensive  enzymes  are  proteolytic  enzymes. 
Abderhalden3  claims  that  the  parenteral  introduction  of  any  foreign 
protein  into  the  animal  body  will  be  followed  by  the  appearance  in  the 
blood  of  a  defensive  enzyme  capable  of  digesting  that  protein.  He  also 
claims  that  in  pregnancy  the  passage  into  the  blood,  of  protein  material 
in  the  form  of  cells  and  fragments  of  chorionic  villi  will  cause  the 
appearance  in  the  blood  of  a  defensive  proteolytic  enzyme  capable  of 
digesting  placenta  protein.  The  Abderhalden  reaction  for  pregnancy 
is  based  upon  this  hypothesis.  The  reaction  has  been  widely  employed 
and  much  has  been  said  both  for  and  against  its  accuracy. 4  Modifications 
of  the  reaction  have  been  suggested  as  aids  in  the  diagnosis  of  various 

1  Substance  acted  upon.    See  Lippmann:  Ber.  d.  Deutsch.  Chem.  Ges.,  36,  331,  1903. 

2  Armstrong  suggests  the  use  of  the  termination  "clastic"  instead  of  "lytic."    He  calls 
attention  to  the  fact  that  amylolytic,  in  analogy  with  electrolytic,  means  "decomposition  by 
means  of  starch"  and  is  therefore  a  misnomer.    He  suggests  the  use  of  amyloclastic, 
proteoclastic,  etc. 

*  Abwehrfermenle  des  tierischen  Organismus,  5th  Ed.,  Berlin,  1915,  Springer. 

4Bronfenbrenner:  Jour.  Am.  Med.  Assn.,  65,  1268,  1915.  Van  Slyke:  New  York  Med. 
Jour.,  103,  219,  1916.  Taylor:  Jour.  Biol.  Chem.,  22,  59,  1915.  Hulton:  Jour.  Biol. 
Chem.,  25,  163,  1916.  Kuriyama:  Jour.  Biol.  Chem.,  25,  534,  1916 


PHYSIOLOGICAL  CHEMISTRY 


disorders,  e.g.,  cancer,  tuberculosis,  dementia  praecox,  etc.  These 
are  also  of  doubtful  value.  Recent  work  has  also  thrown  much  doubt 
upon  the  original  contention  of  Abderhalden  as  to  the  formation  of 
protective  enzymes  following  the  parenteral  introduction  of  protein, 
carbohydrates  and  other  substances.  Abderhalden,  however,  maintains 
that  his  original  contention  is  correct.1 

Our  knowledge  regarding  the  distribution  of  enzymes  has  been 
wonderfully  broadened  in  recent  years.  Up  to  within  a  few  years, 
the  real  scientific  information  as  to  the  enzymes  of  the  animal  organism, 
for  example,  was  limited,  in  the  main,  to  a  rather  crude  understanding 
of  the  enzymes  intimately  connected  with  the  main  digestive  func- 
tions of  the  organism.  We  now  have  occasion  to  believe  that  enzymes 
are  doubtless  present  in  every  animal  cell  and  are  actively  associated 
with  all  vital  phenomena.  As  a  preeminent  example  of  such  cellular 
activity  may  be  cited  the  liver  cell  with  its  reputed  complement  of  15-20 
or  more  enzymes. 

A  list  of  the  more  important  enzymes  together  with  their  classes, 
distribution,  substrates  and  end-products  is  given  below. 
CLASSIFICATION  OF   ENZYMES 


Name  and  Class 

Distribution 

Substrate 

End-products 

Carbo'hydrases  
i    A  mylases. 

, 

Carbohydrates  

Maltose. 
Maltose. 
Maltose. 

Starch   dextrin    etc. 

(a)  Pancreatic.  .  .  . 
(amylopsin) 
(b)   Salivary 

Pancreatic  juice  

Starch,  dextrin,  etc  ' 

Saliva.  .  . 

Starch,  dextrin,  etc  
Starch,  dextrin,  etc  • 

(ptyalin) 
(c)    Vegetable  Malt,  rice  fungus,  etc  

2.  Glycoeenase.  .  .  .  Liver,  muscles?..  . 

Glycoeen.  .  ,                         ..Dextrin      and      maltose 

(glucose?) 


3.  Inulase Fungi,  other  plants [Inulin i  Fructose. 

4.  Lactase |  Intestinal  juice  and  mucosa.  Lactose j  Glucose  and  galactose. 


5.  Maltose '  Blood  serum,  liver,  saliva, !  Maltose , 

j  pancreatic  and   intestinal; 
;  juices  and  lymph. 


Glucose. 


6.  Sucrose. . 
(invertase) 


;  Intestinal  juice  and  mucosa.  Sucrose ]  Glucose  and  fructose. 


7.  Zymase !  Yeast jSugars i  Alcohol,  COt,  etc. 


Carboxylase !  Yeast, 


COOH   group   of   aliphatic  Carbon  dioxide, 
acids. 


Deaminases. L.t j  Amino  compounds 


i.  Adenase j  Animal  tissues Adenine. 


Hypoxanthine. 


spleen,  etc. 

3.  Guanase 

Xanthine. 

4.  Urease 

Urea 

Carbon  dioxide  and  am- 

bean, etc. 

monia. 

Glucosidases  

Glucosides  (amygdalin  and 

Plants  

others)  . 
/3-glucosides  

Glucose,  etc. 

2.  Invertase  

Yeast   etc 

Glucose,  etc. 

1  Abderhalden:  Correspondenz-Blatt  fur  Schweizer  Aerzte,  47,  1745,  1917. 


ENZYMES   AND    THEIR   ACTION 
CLASSIFICATION  OF  ENZYMES.— Continued 


Name  and  Class 

Distribution 

Substrate 

End-products 

;Fats. 


Lipases 

1.  Autolytic Animal   tissues 

2.  Pancreatic Pancreatic  juice 

(steapsin) 

3.  Vegetable Castor  bean,  etc Fats Fatty  acid  and  glycerol. 


Fats Fatty  acid  and  glycerol 

Fats Fatty  acid  and  glycerol. 


Nucleuses " 

1.  Nucleicacidase. .  Intestinal  mucosa  and  juice, 

;  other  tissues. 

2.  Nucleotidase. . .  Intestinal  mucosa  and  juice, 

;  other  tissues. 

3.  Nucleosidase. . .  Tissues 


i  Nucleic  acid  and  derivatives; 
Nucleic  acid Nucleotides. 

Nucleotides Phosphoric  acid  and  nu- 

i  cleosides. 
Nucleosides '-•  Carbohydrate  and  bases. 


Oxidases, 

1.  Catalase Plant  and  animal  tissues. . 

2.  Laccase Lac  tree,  fungi,  etc 


3.  Peroxidase , Plant  and  animal  tissues. 


Hydrogen  peroxide Oxygen  or  oxidation  prod- 
ucts. 

|Polyhydric  para-phenols  as  Oxidation  products. 
'  hydroquinol     and     pyro-i 

Organic  peroxides Oxygen  or  oxidation  prod- 
ucts. 


4.  Purine-oxidases.       -                                                Purines. 
(a)  Hypoxanthine  Animal  tissues.       IHvnnTa-nthine  

Xanthine. 

Allantoin. 
Uric  acid. 

Homogentisic  acid,  etc. 

oxidase. 

Uric  acid  \...  

Xanthine                       .    .  . 

oxidase. 
5.  Tyrosinase  Plant  and  animal  tissues..  . 

Tyrosine  

Polypeptids  

i.  Erepsin  'Intestinal  mucosa  and  juice, 
other  tissues. 

Peptids,  also  peptones  and  Simpler     ^peptids      and 
casein.                                       amino  acids. 

Phytase                        Rice  bran  liver  blood. 

Phytin   

Inositol  and  phosphoric 
acid. 

Proteases. 

Paracasein. 
Paracasein. 

Fibrin. 
Proteoses,  peptones,  and 
peptides.  * 
Proteoses,  peptones,'  pep- 
tides,  amino-acids. 

Proteoses,  peptones,  etc 
Proteoses.  peptones,  etc 

Proteins  in  solution  

Casein                            . 

(gastric) 

(pancreatic) 
(c)    Thrombin          Blood 

Proteins 

(acid-protease)   j 
3    Trypsin                'Pancreatic  juice   

(alkali-protease)  ; 
4.  Vegetable    pro- 
teases. 

(b)   Papain              Pawpaw 

Proteins  

(papayotin). 
Purinases  (see  Purine! 
Oxidases  and  Pur-| 
ine  Deaminases). 

In  text-book  discussions  of  the  enzymes  it  is  customary  to  say  that 
very  little  is  known  regarding  the  chemical  characteristics  of  these  sub- 
stances since  no  member  of  the  enzyme  group  has,  up  to  the  present 
time,  been  prepared  in  an  absolutely  pure  condition.  Apparently,  how- 
ever, from  the  nature  of  the  facts  in  the  case,  it  would  be  much  more 
accurate  to  say  that  we  absolutely  do  not  know  whether  a  specific  enzyme 
has,  or  has  not,  been  prepared  in  a  pure  state.  (Some  authors,  like 
Arthus,  have  assumed  that  enzymes  are  not  chemical  individuals,  but 
properties  conferred  upon  bodies?)  The  enzymes  are  very  difficult  to 
prepare  in  anything  like  a  condition  approximating  purity,  since  they 
are  very  prone  to  change  their  nature  during  the  process  by  which  the 


6  PHYSIOLOGICAL  CHEMISTRY 

investigator  is  attempting  to  isolate  them.  For  this  reason  we  have 
absolutely  no  proof  that  the  final  product  obtained  is,  or  is  not,  in  the 
same  state  of  purity  it  possessed  in  the  original  cell.  Some  of  the  en- 
zymes are  more  or  less  closely  associated  with  the  proteins  from  the  fact 
that  they  are  both  formed  in  every  cell  as  the  result  of  the  cellular  ac- 
tivity, both  may  be  removed  from  solution  by  "salting-out,"  both  are 
for  the  most  part  non-diffusible  and  are  probably  very  similar  as  re- 
gards elementary  composition.  Hence  in  the  preparation  of  some 
enzymes  it  is  extremely  difficult  to  make  an  absolute  separation  from 
the  protein.  Most  of  the  evidence  points  to  the  protein  character  of 
enzymes.1  Under  certain  conditions  enzymes  are  readily  adsorbed  by 
shredded  protein  material,  such  as  fibrin,  and  may  successfully  resist 
the  most  prolonged  attempts  at  washing  them  free.  We  may  sum- 
marize some  of  the  properties  of  the  great  body  of  enzymes  as  follows: 
Enzymes  are  soluble  in  dilute  glycerol,  sodium  chloride  solution, 
dilute  alcohol,  and  water,  and  precipitable  by  ammonium  sulphate 
and  strong  alcohol.  Their  presence  may  be  proven  from  the  nature 
of  the  end-products  of  their  action  and  not  through  the  agency  of  any 
chemical  test.  They  are  colloidal  and  non-diffusible,  and  occur  closely 
associated  with  protein  material  with  which  they  generally  possess  many  v 
properties  in  common.  Each  enzyme  shows  the  greatest  activity  at  a 
certain  temperature  called  the  optimum  temperature;  there  is  also  a 
minimum  and  a  maximum  temperature  for  each  specific  enzyme.  Their 
action  is  inhibited  by  sufficiently  lowering  the  temperature,  although 
some  activity  may  be  shown  at  o°C.  or  even  at  lower  temperatures 
and  freezing  does  not,  in  most  cases,  permanently  injure  enzymes. 
Most  enzymes,  if  in  solution,  are  entirely  destroyed  by  subjecting  them 
to  a  temperature  of  7o°-ioo°C.  The  best  known  enzymes,  whether 
derived  from  warm-blooded  or  cold-blooded  animals,  are  most  active 
between  35°-45°C.  The  nature  of  the  surrounding  media  alters  the 
velocity  of  the  enzymatic  action,  some  enzymes  being  more  active  in 
acid  solution  whereas  others  require  an  alkaline  fluid. 

Many  of  the  more  important  enzymes  do  not  occur  performed 
within  the  cell,  but  are  present  in  the  form  of  a  zymogen  or  mother- 
substance.  In  order  to  yield  the  active  enzyme  this  zymogen  must  be 
transformed  in  a  certain  specific  manner  and  b}»  a  certain  specific  sub- 
stance. This  transformation  of  the  inactive  zymogen  into  the  active 
enzyme  is  termed  activation.  For  instance,  the  zymogen  of  the  enzyme 
pepsin  of  the  gastric  juice,  termed  pepsinogen,  is  activated  by  the  hydro- 
chloric acid  secreted  by  the  gastric  cells  (see  page  140),  whereas  the  acti- 
vation of  the  trypsinogen  of  the  pancreatic  juice  is  brought  about  by  a 

1  Others  seem  to  be  like  the  substrate  on  which  they  act,  e.g.,  carbohydrate. 


ENZYMES   AND   THEIR  ACTION  7 

substance  termed  enter okinase1  (see  page  199).  These  are  examples  of 
many  well-known  activation  processes  going  on  continually  within  the 
animal  organism.  The  agency  which  is  instrumental  in  activating  a 
zymogen  is  generally  termed  a  zymo-exciter  or  a  kinase.  In  the  cases 
cited  hydrochloric  acid  would  be  termed  a  zymo-exciter  and  entero- 
kinase  would  be  termed  a  kinase. 

After  filtering  yeast  juice,  prepared  by  the  Buchner  process  (see  page 
2),  through  a  Martin  gelatin  filter,  Harden  and  Young  showed  that 
the  colloids  left  behind  and  the  filtrate  were  both  inactive  fermenta- 
tively.  Upon  treating  the  colloid  material  (enzyme)  with  some  of  the 
filtrate,  however,  the  mixture  was  shown  to  be  able  to  bring  about  pro- 
nounced fermentation.  It  is  believed  that  a  co-enzyme  present  in  the 
filtrate  was  the  efficient  agent  in  the  transformation  of  the  inactive 
enzyme.  It  is  necessary  to  make  frequent  renewals  of  the  co-enzyme 
in  order  to  maintain  continuous  fermentatioif.  Et  was  further  shown 
that  this  co-enzyme,  in  addition  to  being  diffusible,  was  not  destroyed 
by  boiling  and  that  it  disappeared  from  yeast  juice  when  this  latter 
was  fermented  or  allowed  to  undergo  autolysis.  The  exact  nature  of 
this  co-enzyme  of  zymase  is  unknown.  The  co-enzyme  action,  in  this 
case,  is  probably  dependent  upon  the  presence  of  two  individual 
agencies,  one  of  which  is  phosphates. 

It  has  been  shown  by  Loevenhart  that  the  property  of  acting  as  a 
pancreatic  lipase  co-enzyme  is  vested  in  bile  salts,  and  Magnus  has 
further  shown  that  the  synthetic  salts  are  as  efficient  in  this  regard  as 
the  natural  ones.  A  few  other  instances  of  co-enzyme  demonstrations 
have  been  reported. 

Electrolytes  are  very  important  factors  in  facilitating  or  inhibiting 
enzyme  action.2  For  example,  the  Cl  ion  in  proper  amount  facilitates 
the  action  of  amylases.3  In  fact  the  presence  of  the  Cl  or  Br  ion  is 
apparently  absolutely  essential  to  the  activity  of  pancreatic  amylase, 
inasmuch  as  dialysis  renders  this  enzyme  inactive,  the  activity  return- 
ing on  the  addition  of  sodium  chloride.4  The  acidity  or  hydrogen  ion 
concentration  of  the  solution  also  exerts  much  influence  on  the  activity 
of  enzymes.  It  has  been  demonstrated  in  the  case  of  certain  enzymes, 
at  least,  that  the  continuous  vibration  or  shaking  of  their  solutions  tends 
to  produce  a  destruction  of  the  enzyme.  Ultraviolet  light  also  has  a 
destructive  action  on  enzymes. 

The  so-called  "specificity"  of  enzyme  action  is  an  interesting  and 
mportant  fact.  That  enzymes  are  very  specific  as  to  the  character  of 

1  According  to  Delezenne,  trypsinogen  may  be  rapidly  activated  by  soluble  calcium  salts. 

2  For  literature,  see  Kendall  and  Sherman:  Jour.  Am.  Chem.  Soc.,  32,  1087,  1910. 
3Wohlgemuth:  Biochemische  Zeitschrift,  9,  10,  1908. 

4Bierry:  Ibid.,  40,  357,  1912. 


8  PHYSIOLOGICAL  CHEMISTRY 

the  substrate,  or  substance  acted  upon,  is  well  known.  Emil  Fischer 
investigated  this  problem  of  specificity  extensively  in  connection  with 
the  fermentation  of  sugars  and  reached  the  conclusion  that  enzymes, 
with  the  possible  exception  of  certain  oxidases,  can  act  only  upon  such 
substances  as  have  a  specific  stereo-isomeric  relationship  to  themselves. 
He  considers  that  the  enzyme  and  its  substrate  must  have  an  inter- 
relation, such  as  the  key  has  to  the  lock,  or  the  reaction  does  not  occur. 
Fischer  was  able  to  predict,  in  certain  definite  cases,  from  a  knowledge 
of  the  constitution  and  stereo-chemical  relationships  of  a  substance, 
whether  or  not  it  would  be  acted  upon  by  a  certain  enzyme.  An  appli- 
cation of  this  specificity  of  enzyme  action  may  be  seen  in  the  well-known 
facts  that  certain  enzymes  act  on  carbohydrates,  others  on  fats,  and 
others  on  protein;  and,  moreover,  that  the  group  of  those  which  trans- 
form carbohydrates,  for  example,  is  further  subdivided  into  specific  en- 
zymes each  of  which  has  the  power  of  acting  alone  upon  some  one  sugar. 

It  has  been  conclusively  shown,  in  the  case  of  certain  enzymes,1 
at  least,  that  their  action  is  a  reversible  one  and  is,  in  all  its  main  fea- 
tures, directly  analogous  to  the  reversible  reactions  produced  by  chem- 
ical means.  For  instance,  in  the  saponification  of  ethyl-butyrate  by 
means  of  pancreatic  lipase,  it  has  been  shown  that  upon  the  tormation 
of  the  end-products  of  the  reaction,  i.e.,  butyric  acid  and  ethyl  alcohol, 
there  is  reversion2  and  the  reaction  is  stationary.  This  does  not  mean 
there  are  no  chemical  changes  going  on,  but  simply  indicates  that 
chemical  equilibrium  has  been  established,  and  that  the  change  in  one 
direction  is  counterbalanced  by  the  change  in  the  opposite  direction. 
Pancreatic  lipase  was  one  of  the  first  enzymes  to  have  the  reversibility 
of  its  reaction  clearly  demonstrated.3  A  knowledge  of  the  fact  that 
lipase  possesses  this  reversibility  of  action  is  of  extreme  physiological 
importance  and  aids  us  materially  in  the  explanation  of  the  processes 
involved  in  the  digestion,  absorption,  and  deposition  of  fats  in  the 
animal  organism  (see  page  181). 

Euler4  claims  that  enzymatic  cleavage  and  synthesis  are  often  brought 
about  by  two  different  components  of  an  enzyme  preparation.  He 
would  indicate  this  fact  by  giving  the  termination  -ese  to  those  enzymes 
exerting  a  synthetic  function.  For  example,  the  enzyme  which  catalyzes 
the  formation  of  nitriles  Euler  would  call  mtnlese  in  distinction  from 
nitnlase  which  splits  nitriles.  He  would  further  designate  as  phos- 

1  This  is  probably  a  general  condition. 

2  The  re-synthesis  of  ethyl-butyrate  from  its  hydrolysis  products.     This  may  be  indi- 
cated thus: 

C3H7COO.C2H5  +  H20  ±5  C3H7COOH  +  C2H5OH. 

Ethyl-butyrate.  Butyric  acid.          Ethyl  alcohol. 

•  *  This  principle  was  first  demonstrated  in  connection  with  the  enzyme  maltase  (see  p.  56). 
4 Euler:  Zeitschrift  fur  physiologische  Chemie,  74,  13,  1911. 


ENZYMES   AND   THEIR   ACTION  9 

ph&tese  the  enzyme  which  builds  up  phosphoric  acid  esters  of  carbo- 
hydrates in  distinction  from  phosphates  which  causes  their  cleavage. 
In  the  same  way  he  would  differentiate  the  lipolytic  enzymes  into  Upases 
and  lipeses. 

In  respect  to  many  enzymes  it  has  been  found  that  the  law  govern- 
ing the  action  of  inorganic  catalyzers  is  directly  applicable,  i.e.,  that 
the  intensity  is  almost  directly  proportional  to  the  concentration  of  the 
enzyme.  In  the  case  of  enzymes,  however,  there  is  a  difference  in  that  a 
maximum  intensity  is  soon  reached  and  that  subsequent  concentration 
of  the  enzyme  is  productive  of  no  further  increase  in  intensity.  En^ 
zymes  which  have  been  shown  to  obey  this  linear  law  are  lipase,  sucrase, 
rennin,  and  trypsin.  In  certain  instances,  where  this  law  of  direct 
proportionality  between  the  intensity  of  action  and  the  concentration 
of  enzymes  does  not  hold,  it  has  been  found  that  the  Schutz-Borissow 
law,  first  experimentally  demonstrated  by  E,  Schutz,  was  applicable. 
This  is  to  the  effect  that  the  intensity  is  directly  proportional  to  the 
square  root  of  the  concentration,  or  conversely,  that  the  relative  con- 
centrations of  enzyme  preparations  are  directly  proportional  to  the  squares 
of  the  intensities.1 

It  has  been  shown  that  there  are  certain  substances  which  possess 
the  property  of  directly  inhibiting  or  preventing  the  action  of  a  cata- 
lyzer. These  are  called  anti-catalyzers  or  paralyzers  and  have  been  com- 
pared with  the  anti-toxins.  Related  to  this  class  of  anti-catalytic  agents 
stand  the  anti-enzymes.  The  first  anti-enzyme  to  be  reported  was  the 
anti-rennin  of  Morgenroth.  This  was  produced  by  injecting  into  an 
animal  increasing  doses  of  rennet  solution,  whereupon  an  "anti" 
substance  was  subsequently  found  both  in  the  serum  and  in  the  milk, 
which  prevented  the  enzyme  rennin  from  exerting  its  normal  activity 
in  the  presence  of  casein.  In  other  words,  anti-rennin  had  been 
formed  in  the  serum  of  the  animal,2  through,  the  repeated  injections  of 
rennet  solution.  Since  the  discovery  of  this  anti-enzyme,  anti-bodies 
have  been  demonstrated  for  pepsin,  trypsin,  lipase,  urease,  amylase, 
laccase,  tyrosinase,  emulsin,  papain,  and  thrombin.  According  to 
Weinland,  the  reason  why  the  stomach  does  not  digest  itself  is,  that 
during  life  there  is  present  in  the  mucous  membrane  of  the  stomach  an 
anti-enzyme  (anti-pepsin)  which  has  the  property  of  inhibiting  the  action 
of  pepsin.  A  similar  substance  (anti-try p sin)  is  present  in  the  intestinal 
mucosa  as  well  as  in  the  tissues  of  various  intestinal  worms.  It  is 
probable  that  among  the  substances  commonly  classified  as  anti- 
enzymes  are  included  inhibitory  agents  of  widely  differing  characters. 

1  This  Schutz-Borissow  law  is  not  generally  applicable. 

2  Serum  is  normally  anti-try ptic. 


10  PHYSIOLOGICAL  CHEMISTRY 

The  investigations  of  Ehrlich1  and  of  Neuberg2  have  served  to  cause 
a  complete  revision  of  our  ideas  regarding  yeast  fermentation.  Ehrlich, 
for  example,  has  shown  that  yeast  will  liberate  ammonia  from  amino  acids 
and  leave  behind  a  non-nitrogenous  complex.  Among  these  complexes 
amyl  alcohol,  succinic  acid  and  others  may  be  mentioned.  Thus,  amyl 
alcohol  results  from  the  fermentation  of  leucine,  whereas  ethyl  alcohol 
results  from  the  fermentation  of  sugar.  Neuberg  has  demonstrated  the 
presence  in  the  yeast  of  an  enzyme  termed  carboxylase  which  has  the 
property  of  splitting  o/  carbon  dioxide  from  the  carboxyl  group  of  amino 
and  other  aliphatic  acids.  The  findings  mentioned  above  constitute  the 
basis  for  much  important  work  on  so-called  "  sugar-free  fermentation." 

For  a  more  extended  consideration  of  enzymes  the  student  is  referred 
to  the  following  sources. 

BAYLISS. — The  Nature  of  Enzyme  Action,  Longmans,  Green  and 
Co.,  New  York  and  London. 

BEATTY. — The  Method  of  Enzyme  Action,  P.  Blakiston's  Son 
and  Co.,  Philadelphia. 

COHNHEIM. — Enzymes,  Wiley  and  Sons,  New  York. 

DUCLAUX. — Traite  de  Microbiologie,  Masson  and  Co.,  Paris. 

EFFRONT. — (a)  Enzymes  and  their  Applications,  Translated  by 
Fresco tt,  Wiley  and  Sons,  New  York,  (b)  Biochemical  Catalysts 
in  Life  and  Industry.  Proteolytic  Enzymes,  Translated  by  Prescott 
and  Venable,  Wiley  and  Sons,  New  York. 

EULER. — (a)  Allgemeine  Chemie  der  Enzyme,  Bergmann,  Wies- 
baden, (b)  Ergebnisse  der  Physiologic,  (c)  General  Chemistry  of  the 
Enzymes,  Translated  by  Pope,  Wiley  and  Sons. 

FALK. — The  Chemistry  of  Enzyme  Actions,  The  Chemical  Catalog 
Co.,  New  York,  1921. 

OPPENHEIMER. — Die  Fermente  und  Ihre  Wirkungen,  Vogel,  Leipzig. 

SAMUELY. — Handbuch  der  Biochemie  des  Menschen  und  der  Thiere 
(Oppenheimer) ,  Gustav  Fischer,  Jena. 

WOHLGEMUTH. — Grundriss  der  Fermentmethoden,  Springer,  Berlin 

EXPERIMENTS  ON  ENZYMES  AND  ANTI-ENZYMES 
A.  Experiments  on  Enzymes3 

I.  AMYLASES 

i.  Demonstration  of  Salivary  Amylase.4— To  25  c.c.  of  a  i  per  cent  starch 
paste  in  a  small  beaker,  add  5  drops  of  saliva  and  stir  thoroughly.  At  intervals 

1  Ehrlich:  Biochemische  Zeitschrift,  36,  477,  1911.  - 

'Neuberg  and  Collaborators:  Biochemische  Zeitschrift,  31,  170;  32,  323;  36  (60,  68,  and 
76),  1911. 

3  If  it  is  deemed  advisable  by  the  instructor  to  give  all  the  practical  work  upon  enzymes 
at  this  point  in  the  course,  additional  experiments  will  be  found  in  Chapters  III,  VI,  VII, 
X  and  XI.  ^ 

4  For  a  discussion  of  this  enzyme  see  p.  54. 


ENZYMES   AND   THEIR   ACTION  II 

of  a  minute  remove  a  drop  of  the  solution  to  one  of  the  depressions  of  a  test-tablet 
and  test  by  the  iodine  test.1  If  the  blue  color  with  iodine  still  forms  after  five 
minutes,  add  another  5  drops  of  saliva. 

The  opalescence  of  the  starch  solution  should  soon  disappear, 
indicating  the  formation  of  soluble  starch  (amidulin)  which  gives  a  blue 
color  with  iodine.  This  body  should  soon  be  transformed  into  erythro- 
dextrin  which  gives  a  red  color  with  iodine,  and  this,  in  turn,  should 
pass  into  achroodextrin  which  gives  no  color  with  iodine.  This  point  is 
called  the  achromic  point.  When  this  point  is  reached  test  by  Fehling's 
test2  to  show  the  production  of  a  reducing  substance  (maltose).  A 
positive  Fehling's  test  may  be  obtained  while  the  solution  still  reacts  red 
with  iodine,  inasmuch  as  some  sugar  is  formed  from  the  soluble  starch 
coincidently  with  the  formation  of  the  erythrodextrin.  For  further 

discussion  of  the  transformation  of  starch  see  page  55. 

> 

2.  Demonstration  of  Pancreatic  Amylase.3 — Proceed  exactly  as  indicated  above 
in  the  Demonstration  of  Salivary  Amylase  except  that  the  saliva  is  replaced  by  5  c.c. 
of  pancreatic  extract  prepared  as  described  on  p.  192.*    Pancreatic  amylase  trans- 
forms the  starch  in  a  manner  entirely  analogous  to  the  transformation  resulting 
from  the  action  of  salivary  amylase. 

3.  Preparation  of  Vegetable  Amylase. — Extract  finely  ground  malt  with  water, 
filter  and  subject  the  filtrate  to  alcoholic  fermentation  by  means  of  yeast.    When 
fermentation  is  complete  filter  off  the  yeast  and  precipitate  the  amylase  from  the 
filtrate  by  the  addition  of  alcohol.    The  precipitate  may  be  filtered  off  and  ob- 
tained hi  the  form  of  a  fine  white  powder. 

A  purer  preparation5  is  obtained  if  the  solution  is  dialyzed  against 
water  at  about  io°C.  (in  the  ice-box)  for  24  hours,  filtered  and  pre- 
cipitated with  alcohol  or  acetone.  First  alcohol  or  acetone  to  make  a  50 
per  cent  solution  is  added,  the  precipitate  thus  formed  being  rejected, 
while  the  precipitate  formed  on  the  addition  of  sufficient  alcohol  or 
acetone  to  make  a  final  concentration  of  65-70  per  cent  is  preserved,  and 
dried  in  a  vacuum  desiccator  at  a  low  temperature. 

4.  Demonstration  of  Vegetable  Amylase. — This  enzyme  may  be  demon- 
strated according  to  the  directions  given  under  Demonstration  of  Salivary  Amylase, 
page  10,  with  the  exception  that  the  saliva  used  in  that  experiment  is  replaced  by 
an  aqueous  solution  of  the  vegetable  amylase  powder  prepared  as  described 
above.6 

1  See  p.  43- 

2  See  p.  25. 

8  For  a  discussion  of  this  enzyme  see  p.  190. 

4  Commercial  preparations  of  pancreatic  amylase  may  be  substituted  for  the  pancreatic 
extract. 

6  Sherman  and  Schlesinger:  /.  Am.  Ch.  Soc.,  35,  1617,  1915. 

6  If  desired  the  first  aqueous  extract  of  the  original  malt  may  be  used  in  this  demonstra- 
tion. Commercial  taka-diastase  may  also  be  employed 


12  PHYSIOLOGICAL   CHEMISTRY 

H.  PROTEASES 

1.  Preparation  of  Gastric  Protease.1 — Treat  the  finely  comminuted  mucosa  of 
a  pig's  stomach  with  0.4  per  cent  hydrochloric  acid  and  extract  at  38°C.  for 
24-48  hours.    The  filtrate  from  this  mixture  constitutes  a  very  satisfactory  acid 
extract  of  gastric  protease  (see  page  143). 

2.  Demonstration  of  Gastric  Protease. — Introduce  some  protein  material 
(fibrin,  coagulated  egg-white,  or  washed  lean  beef)  into  the  acid  extract  of  gastric 
protease  prepared  as  above  described,2  add  an  equal  volume  of  0.4  per  cent 
hydrochloric  acid  and  place  the  mixture  at  38°C.  for  2-3  days.    Identify  the 
products  of  digestion  according  to  directions  given  on  page  144. 

Carmine-fibrin  may  also  be  used  in  this  test.  This  is  prepared 
by  running  fibrin  through  a  meat  chopper  washing  carefully  and  placing 
in  a  J^  per  ( cent  ammoniacal  carmine  solution  (very  little  excess  am- 
monia should  be  present)  until  the  maximum  coloration  of  the  fibrin 
(a  dark  red)  is  obtained.  The  fibrin  is  then  washed  in  water  and  water 
acidified  with  acetic  acid.  It  is  preserved  under  glycerol. 

To  15  c.c.  of  the  solution  to  be  tested  add  a  small  amount  of  the 
carmine  fibrin  and  allow  to  digest  at  room  temperature.  Digestion  will 
be  ^hown  by  the  setting  free  of  carmine  with  coloration  of  the  solution. 
This  is  a  delicate  test  for  pepsin.  A  control  should  be  run  using  acid  of 
same  strength  as  that  of  enzyme  solution  tested. 

3.  Preparation   of   Pancreatic   Protease.3— A   satisfactory   extract   of   this 
enzyme  may  be  made  from  the  pancreas  of  a  pig  or  sheep  according  to  the  direc- 
tions given  on  page  192. 

4.  Demonstration  of  Pancreatic  Protease.— Into  an  alkaline  extract  of  pan- 
creatic protease,4  prepared  as  directed  on  page  192,  introduce  some  fibrin,  coagu- 
lated egg-white  or  lean  beef  and  place  the  mixture  at  38°C.  for  2-5  days.6    At 
the  end  of  that  period  separate  and  identify  the  end-products  of  the  action  of  pan- 
creatic protease  according  to  the  directions  given  on  page  192. 

Congo-red  fibrin  may  be  used  in  this  test.  This  may  be  prepared 
by  placing  fibrin  in  faintly  alkaline  congo-red  solution  and  heating  to 
8o°C.  The  fibrin  is  then  washed.  A  small  amount  of  this  colored 
fibrin  is  placed  in  the  slightly  alkaline  solution  of  the  enzyme.  Diges- 
tion is  shown  by  a  red  coloration  of  the  solution  due  to  setting  free  of 
congo  red. 

1  Also  called  pepsin,  pepsase,  gastric  protease  and  acid  protease.     For  a  discussion  of  this 
enzyme  see  p.  140. 

2  If  so  desired,  a  solution  of  commercial  pepsin  powder  in  0.2  per  cent  hydrochloric  acid 
may  be  substituted  for  the  extract  of  mucosa. 

3  Also  called  trypsin,  trypsase,  pancreatic  protease  and  alkali  protease.    For  a  discussion 
of  this  enzyme  see  p.  189. 

4  A  0.25  per  cent  sodium  carbonate  solution  of  commercial  trypsin  or  pancreatin  maybe 
substituted. 

6  A  few  c.c.  of  toluene  or  an  alcoholic  solution  of  thymol  should  be  added  to  prevent 
putrefaction. 


ENZYMES   AND    THEIR   ACTION  13 

5.  Demonstration  of  a  Vegetable  Protease. — A  commercial  preparation  of 
papain  (papayolin,  carase  or  papase),  the  protease  of  the  fruit  of  the  pawpaw  (carica 
papaya),  may  be  used  in  this  connection.  Follow  the  same  procedure  as  that  de- 
scribed under  Gastric  Protease  (see  p.  12). 

It  has  been  demonstrated  by  Mendel  and  Blood1  that  the  presence  of  HCN 
will  accelerate  the  proteolytic  activity  of  papain.  It  is  suggested  that  the  HCN 
acts  as  a  so-called  co-enzyme  (see  page  7). 

Vines2  believes  that  "papain"  consists  of  a  mixture  of  two  enzymes,  a  pepsin 
and  an  erepsin.  Mendel  and  Blood  do  not  consider  the  evidence  on  this  point  as 
conclusive. 

m.  LIPASES 

1.  Preparation  of  Pancreatic  Lipase.3 — An  extract  of  this  enzyme  may  be 
prepared  from  the  pancreas  of  the  pig  or  sheep  according  to  the  directions  given 
on  page  192.* 

2.  Demonstration  of  Pancreatic  Lipase. — Into  each  of  two  test-tubes  intro- 
duce 10  c.c.  of  milk  and  a  small  amount  of  litmus  powder.    To  the  contents  of  one 
tube  add  3  c.c.  of  a  neutral  extract  of  pancreatic  lipase  and  to  the  contents  of  the 
other  tube  add  3  c.c.  of  a  boiled  neutral  extract  of  pancreatic  lipase.    Keep  the 
tubes  at  38°C.  and  watch  for  color  changes. 

The  blue  color  of  the  litmus  powder  will  gradually  give  place  to  a 
red.  This  change  in  color  of  the  litmus  from  blue  to  red  has  been 
brought  about  by  the  fatty  acid  which  has  been  produced  through  the 
lipolytic  action  exercised  by  the  lipase  upon  the  milk  fats. 

3.  Preparation  of  Vegetable  Lipase. — This  enzyme  may  be  readily  prepared 
from  castor  beans,  several  months'  old,  by  the  following  procedure.6  Grind  the 
shelled  beans  very  fine6  and  extract  for  twenty-four-hour  periods  with  alcohol-ether 
and  ether,  in  turn.  •  Reduce  the  semi-fat-free  material  to  the  finest  possible  consist- 
ency by  means  of  mortar  and  pestle  and  pass  this  material  through  a  sieve  of  very 
fine  mesh.     Place  this  material  in  a  Soxhlet  extractor  and  extract  for  one  week. 
This  fat-free  powder  may  then  be  used  to  demonstrate  the  action  of  vegetable 
lipase.    Powder  prepared  as  described  may  be  used  in  quantitative  tests.     For 
ordinary  qualitative  tests  it  is  not.  necessary  to  remove  the  last  traces  of  fat  and 
therefore  the  extraction  period  in  the  Soxhlet  apparatus  may  be  much  shortened. 

4.  Demonstration  of  Vegetable  Lipase. — The  lipolytic  action  of  the  lipase  pre- 
pared from  the  castor  bean,  as  just  described,  may  be  demonstrated  in  a  manner 
entirely  analogous  to  that  used  hi  the  Demonstration  of  Pancreatic  Lipase,  see 
above.    Proceed  as  indicated  in  that  experiment  and  substitute  the  vegetable 
lipase  powder  for  the  neutral  extract  of  pancreatic  tipase.     The  type  of  action  is 
entirely  analogous  in  the  two  instances. 

1  Mendel  and  Blood:  Journal  of  Biological  Chemistry,  8,  177,  1910. 

2  Vines:  Annals  of  Botany,  19,  174,  1905. 

'Also  called  steapsin.  For  a  discussion  of  the  enzyme  see  p.  191.  A  very  active  lipo- 
lytic extract  may  also  be  prepared  from  the  liver. 

4  If  preferred,  a  glycerol  extract  may  be  prepared  according  to  the  directions  given  by 
Kanitz  (Zeitschrift  fur  physiologische  Chemie,  46,  482,  1906)  or  commercial  pancreatin 
may  be  employed. 

5  A.  E.  Taylor:  On  Fermentation;  University  of  California  Publications,  1907. 

6  The  shells  should  be  removed  without  the  use  of  water.    These  beans  are  poisonous, 
due  to  their  content  of  ricin. 


14  PHYSIOLOGICAL   CHEMISTRY 

An  experiment  similar  to  Experiment  4,  page  197,  may  also  be  tried  if  desired. 
In  this  experiment  0.2  c.c.  of  either  ethyl  butyrate  or  amyl  acetate  may  be  employed. 

IV.  INVERTASES1 

1.  Preparation  of  Vegetable  Sucrase.2 — Thoroughly  grind  about  100  grams  of 
brewer's  or  baker's  yeast  in  a  mortar  with  sand.    Spread  the  ground  yeast  in  thin 
layers  on  glass  or  porous  plates  and  dry  it  rapidly  in  a  current  of  dry,  warm  air. 
Powder  this  dry  yeast,  extract  it  with  distilled  water  and  filter.    Pour  the  filtrate 
into  acetone,  stir  and  after  permitting  the  acetone  mixture  to  stand  for  a  few  min- 
utes filter  on  a  Buchner  funnel.    The  resulting  precipitate,  after  drying  and 
pulverizing,  may  be  used  to  demonstrate  vegetable  sucrase. 

2.  Demonstration  of  Vegetable  Sucrase. — To  about  5  c.c.  of  a  i  per  cent 
solution  of  sucrose  in  a  test-tube  add  a  small  amount  of  the  sucrase  powder  pre- 
pared as  directed  above.    Place  the  tube  at  38°C.  for  24-72  hours  and  at  the  end 
of  that  period  test  the  solution  by  Fehling's  test  (see  page  25.)     Reduction  indi- 
cates that  the  active  sucrase  powder  has  transformed  the  non-reducing  sucrose 
into  glucose  and  fructose,  and  these  sugars,  in  turn,  have  reduced  the  Fehling 
solution. 

For  other  experiments  on  Invertases,  see  Chapter  XI. 

V.  OXIDASES3 

i.  Demonstration  of  Oxidase. — Oxidases  or  oxidizing  enzymes  con- 
stitute a  very  important  group  of  intracellular  enzymes.  They  are 
intimately  connected  with  the  oxidation  processes  in  the  plant  and  ani- 
mal organisms. 

1.  Cut  a  thin  slice  from  a  freshly  pared  potato,  place  it  on  a  watch  glass  and 
examine  at  intervals  during  the  laboratory  exercise.    Note  that  the  colorless 
potato  gradually  becomes  brown. 

This  is  due  to  the  oxidation  of  para-oxyphenyl  substances  such  as 
tyrosine,  in  the  cells  and  in  the  intracellular  juice  of  the  potato.  Two 
oxidases  which  have  the  power  of  accelerating  the  oxidation  of  para- 
oxyphenyl  compounds  are  called  tyrosinase  and  laccase. 

2.  Preparation  of  Potato  Extract. — Scrape  a  pared  potato  by  means  of  a  knife 
or  scalpel  or  comminute  the  potato  substance  by  means  of  a  grater.    Extract  the 
macerated  potato  substance  by  means  of  water.    Strain  through  cheese  cloth  and 
filter  the  extract.    Make  an  iodine  test  on  the  solid  substance  (see  Starch,  page 
45),  and  save  the  water  extract  for  use  in  the  following  experiments. 

3.  Oxidation  of  Para-oxyphenyl  Compounds  by  Potato  Oxidases. — Introduce 
5  c.c.  of  filtered  potato  extract  prepared  as  indicated  above,  into  each  of  six  test- 
tubes.    Introduce  additional  reagents  into  the  tubes  according  to  the  following 
series: 

(a)  Potato  extract  -f  5  drops  of  toluene  (control). 

(b)  Potato  extract  +  5  drops  of  ether  (control). 

1  The  inverting  enzymes  of  the  alimentary  tract;  Mendel  and  Mitchell:  American  Journal 
of  Physiology,  20,  81,  1907-08. 

*  For  a  discussion  of  this  enzyme  see  p.  198. 

8  These  experiments  have  been  adapted  from  directions  contained  in  the  Laboratory 
Notes  of  Professor  Gies  of  the  College  of  Physicians  and  Surgeons,  New  York. 


ENZYMES   AND   THEIR   ACTION  15 

(c)  Potato  extract  +  5  drops  of  i  per  cent  phenol  solution. 

(d)  Potato  extract  +  5  drops  of  i  per  cent  "tri-cresol"  solution. 

(e)  Potato  extract  (boiled  and  cooled)  +  5  drops  of  i  per  cent  phenol  solution. 

(f)  Potato  extract  (boiled  and  cooled)  +  5  drops  of  i  per  cent  "tri-cresol" 
solution. 

Shake  the  contents  of  the  six  tubes  thoroughly.  Are  there  any  immediate 
color  changes?  Place  the  tubes  in  your  rack,  and  examine  them  at  the  next 
laboratory  exercise. 

4.  Experiments  with  Typical  Oxidase  Reagents. — Introduce  5  c.c.  of  filtered 
potato  extract  into  each  of  four  test-tubes.  Add  oxidase  reagents  as  follows : 

(a)  Potato  extract  +  10  drops  of  guaiac  solution.1 

(b)  Potato  extract  +  10  drops  of  a-naphthol  solution.2 

(c)  Potato  extract   +   10  drops  of  para-phenylenediamine  hydrochloride 
solutio)n.3 

(d  Potato  extract  -f  5  drops  of  a-naphthol  solution  +  5  drops  of  para- 
phenylenediamine  hydrochloride  solution  -f  5  drops  of  10  per  cent  sodium 
carbonate  (Indophenol  Test). 

Shake  the  contents  of  each  tube  thoroughly  and  note  immediate  color 
changes.  Place  the  tubes  in  the  rack  and  leave  them  undisturbed  until  the 
end  of  the  laboratory  exercise.  Note  any  changes  or  peculiarities  in  the  colora- 
ation  effects,  especially  at  the  surface  of  the  liquid. 

In  tube  (a)  the  guaiaconic  acid  of  the  guaiac  resin  has  been  oxidized 
and  formed  guaiac  blue. 

In  tube  (b)  a  violet  coloration  due  to  the  production  of  di-naphthol 
appears.  The  oxidase  has  oxidized  the  a-naphthol. 

In  tube  (c)  we  have  a  change  whose  chemistry  is  not  well  known. 

In  tube  (d)  we  have  the  production  of  indophenol  from  the  a-naph- 
thol and  the  para-phenylenediamine  hydrochloride  under  the  influence 
of  oxidase.  The  indophenol  is  soluble  in  the  alkaline  solution.  The 
color  gradually  changes  from  red  to  purple  as  the  indophenol 
accumulates. 

The  production  of  the  above  colors  does  not  possess  any  biological 
significance.  These  colors  simply  serve  to  indicate  that  certain  reac- 
tions are  taking  place  which  occur  normally  in  living  cells,  although  in 
the  latter  case  they  are  of  course  unaccompanied  by  any  color  change. 
Intracellular  oxidase  favors  the  utilization  of  oxygen  by  a  cell,  just  as 
the  potato  oxidase  has  facilitated  the  oxidation  of  the  chromogens  in  the 
above  tests. 

VI.  CATALASE 

Demonstration  of  Catalase. — The  various  animal  tissues  as  liver, 
kidney,  blood,  lung,  muscle  and  brain  contain  enzymes  called  catalases 
which  possess  the  property  of  decomposing  hydrogen  peroxide.  Cata- 

1  Made  by  dissolving  0.5  gram  of  guaiac  resin  in  30  c.c.  of  95  per  cent  alcohol. 

2  Made  by  dissolving  i  gram  of  a-naphthol  in  100  c.c.  of  95  per  cent  alcohol. 

3  Dissolve  i  gram  of  para-phenylene  diamine  hydrochloride  in  100  c.c.  of  water. 


1 6  PHYSIOLOGICAL   CHEMISTRY 

lase  brings  about  oxidations  indirectly,  that  is,  only  in  the  presence 
of  hydrogen  peroxide  and  for  this  reason  is  considered  by  some  to  be 
distinct  from  the  true  oxidizing  enzymes.1  Catalase  is  also  found  in 
many  plant  tissues  and  an  extract  of  it  may  be  prepared  from  potatoes. 

1.  Vegetable  Catalase. — Into  each  of  four  test-tubes  place  5  c.c.  of  filtered 
potato  extract  prepared  as  in  Experiment  2,  page  14.    Prepare  a  second  series 
of  four  tubes  (see  4,  p.  15),  but  use  a  boiled  potato  extract.    Prepare  also  a 
third  series  using  water  instead  of  potato  extract.    Now  add  to  each  of  the 
twelve  tubes  5  drops  of  a  3  per  cent  solution  of  hydrogen  peroxide.    While 
the  resultant  lively  effervescence,  characteristic  of  the  action  of  catalase,  is  in 
progress  add  to  each  series  the  four  "Typical  Oxidase  Reagents"  in  the  order 
and  quantities   specified  in  the  preceding   experiment  (4).    Allow  the   tubes 
to  remain  undisturbed  and  carefully  note  comparative  effects  during  the  re- 
mainder of  the  laboratory  exercise.2    Compare  with  results  of  experiment  (4). 

2.  Animal  Catalase. — The  presence  of  this  enzyme  may  also  be  demonstrated 
as  follows:  Introduce  into  a  low,  broad,  wide- mouthed  bottle  some  pulped  liver 
tissue  and  a  porcelain  crucible  containing  neutral  hydrogen  peroxide.3     Connect  the 
bottle  with  a  eudiometer  filled  with  water,  upset  the  crucible  of  hydrogen  peroxide 
upon  the  liver  pulp  and  note  the  collection  of  gas  in  the  eudiometer.    This  gas  is 
oxygen  which  has  been  liberated  from  the  hydrogen  peroxide  through  the  action  of 
the  catalase  of  the  liver  tissue. 

See  next  experiment  for  a  method  for  the  quantitative  determination  of  catalase 
based  on  the  above  principle. 

3.  Quantitative  Determination  of  Catalase.4 — In  the  determination  of  the 
catalase  values  of  tissues  weighed  portions  of  the  tissue  under  examination  should 
be  ground  with  sand  in  a  mortar  then  treated  with  four  volumes  of  chloroform  water 
and  permitted  to  extract  for  24  hours  at  room  temperature.    An  apparatus  such 
as  that  shown  in  Fig.  i  may  be  employed  in  determining  the  catalase  values.6    The 
main  features  of  the  apparatus  are  based  upon  those  of  a  delivery  funnel  for  intro- 
ducing liquids  under  increased  or  diminished  pressure. 

In  making  a  determination  introduce  a  measured  volume  (1-4  c.c.)  of  the  filtered 
extract6  into  the  small  flask  -and  insert  the  modified  Johnson  burette  graduated  to 
5  c.c.  and  containing  50  c.c.  of  hydrogen  peroxide  (Oakland  dioxygen  neutral7  to 
Congo  red)  into  the  neck  of  the  flask.  Fill  the  eudiometer  with  water  and  place  in 
position.  Close  cocks  A  and  C  and  open  cocks  B  and  D  thus  permitting  5  c.c.  of 
the  peroxide  to  flow  into  the  flask.  Shake  the  contents  of  the  flask  briskly8  and 
record  the  volume  of  oxygen  evolved  in  a  two-minute  period  taking  readings  at 
intervals  of  fifteen  seconds. 

1  Reed:  Bot.  Gaz.,  62,  409,  1916. 

2  This  experiment  has  been  adapted  from  one  contained  in  the  Laboratory  Notes  of 
Professor  Gies  of  the  College  of  Physicians  and  Surgeons,  New  York. 

3  Mendel  and  Leaven  worth:  American  Journal  of  Physiology,  21,  85,  1908. 

4  Hawk:  Journal  of  the  American  Chemical  Society,  33,  425,  1911. 

6Another  type  of  apparatus  has  been  suggested  by  Burge  (Am.  Jour.  Physiol.  41,  153, 
1916). 

6  If  less  than  4  c.c.  of  extract  are  used  the  volume  should  be  made  up  to  4  c.c.  by  the 
addition  of  distilled  water. 

7  An  acid  reaction  modifies  the  rate  of  the  oxygen  evolution.     (See  Mendel  and  Leaven- 
worth,  American  Journal  of  Physiology,  21,  85,  1908.) 

8  In  making  a  series  of  comparative  tests  it  is  essential  that  the  shaking  process  should  be 
uniform  from  determination  to  determination. 


ENZYMES   AND   THEIR   ACTION 


Calculation.— When  a  series  of  comparative  tests  are  made  on  different  tissues 
or  on  the  same  tissue  under  different  conditions  it  is  considered  satisfactory  to  make 
a  comparison  of  the  catalase  values  upon  the  basis  of  the  volume  of  oxygen  evolved 
in  a  period  of  two  minutes  from  5  ex.  of  neutral  hydrogen  peroxide  by  means  of  i  c.c. 
of  a  i  :  4  chloroform-water  extract  of  the  tissue. 

B.  Experiments  on  Anti-Enzymes 

i.  Preparation  of  an  Extract  of  Anti-Pepsin.1 — Grind  up  a  number  of  intestinal 
worms  (ascaris)2  with  quartz  sand  in  a  mortar.  Subject  this  mass  to  high  pressure, 
filter  the  resultant  juice  and  treat  it  with  alcohol  until  a  concentration  of  60  per 
cent  is  reached.  If  any  precipitate  forms  it  should  be  filtered  off3  and  alcohol 
added  to  the  filtrate  until  the  concentration  of  alcohol  is  85  per  cent,  or  over.  The 
anti-enzyme  is  precipitated  by  this  concentration.  Permit  this  precipitate  to  stand 


EX) 


FIG.  i. — APPARATUS  FOR  QUANTITATIVE  DETERMINATION  OF  CATALASE. 

for  twenty-four  hours,  then  filter  it  off,  wash  it  with  95  per  cent  alcohol,  absolute 
alcohol,  and  ether,  in  turn,  and  finally  dry  the  substance  over  sulphuric  acid.  The 
sticky  powder  which  results  may  be  used  in  this  form  or  may  be  dissolved  in  water  as 
desired  and  the  aqueous  solution  used.4 

2.  Demonstration  of  Anti-Pepsin.6 — Introduce  into  a  test-tube  a  few  fibrin 
shreds  and  equal  volumes  of  pepsin-hydrochloric  acid6  and  ascaris  extract  made  as 
indicated  above.  Prepare  a  control  tube  in  which  the  ascaris  extract  is  replaced  by 
water.  Place  the  tubes  at  38°C.  Ordinarily  in  one  hour  the  fibrin  in  the  control 
tube  will  be  completely  digested.  The  fibrin  in  the  tube  containing  the  ascaris 

1  Anti-gastric-protease  or  anti-acid-protease. 

2  These  may  be  readily  obtained  from  pigs  at  a  slaughter  house.^ 

3  This  precipitate  consists  of  impurities,  the  anti-enzyme  not  being  precipitated  until  a 
higher  concentration  of  alcohol  is  reached. 

4  The  original  ascaris  extract  possesses  much  greater  activity  than  either  the  powder  or 
the  aqueous  solution. 

6  Martin  H.  Fischer:  Physiology  of  Alimentation,  1907,  p.  134. 

6  Made  by  bringing  0.015  gram  of  pepsin  into  solution  in  7  c.c.  of  water  and  0.23  gram 
of  concentrated  hydrochloric  acid. 

2 


1 8  PHYSIOLOGICAL   CHEMISTRY 

extract  may,  however,  remain  unchanged  for  days,  thus  indicating  the  inhibitory 
influence  exerted  by  the  anti-enzyme  present  in  this  extract. 

3.  Preparation  of  an  Extract  of  Anti-Trypsin.1 — The  extract  may  be  prepared 
from  the  intestinal  worm,  ascaris,  according  to  the  directions  given  on  page  17. 

4.  Demonstration  of  Anti-Trypsin.— Introduce  into  a  test-tube  a  few  shreds 
of  fibrin  and  equal  volumes  of  an  artificial  tryptic  solution2  and  the  ascaris 
extract  made  as  described  on  page  17.    Prepare  a  control  tube  in  which  the 
ascaris  extract  is  replaced  by  water.    Place  the  two  tubes  at  38°C. 

Ordinarily  the  fibrin  in  the  control  tube  will  be  completely  digested 
in  two  hours.  The  fibrin  in  the  tube  containing  the  ascaris  extract  may, 
however,  remain  unchanged  for  days,  thus  indicating  the  inhibitory 
influence  of  the  anti-enzyme. 

Blood  serum  also  contains  anti-trypsin.  This  may  be  demonstrated 
as  follows:  Introduce  equal  volumes  of  serum  and  artificial  tryptic 
solution  (prepared  as  described  above)  into  a  test-tube  and  add  a  few 
shreds  of  fibrin.  Prepare  a  control  tube  containing  boiled  serum.  Place 
in  two  tubes  as  38°C.  It  will  be  observed  that  the  fibrin  in  the  tube 
containing  the  boiled  serum  digests,  whereas  that  in  the  other  tube  does 
not  digest.  The  anti-trypsin  present  in  the  unboiled  serum  has  exerted 
an  inhibitory  influence  upon  the  action  of  the  trypsin. 

C.  Quantitative  Applications 

Methods  for  the  quantitative  determination  of  various  enzymes 
will  be  found  in  the  following  chapters:  Amylase  (Chapter  X); 
Erepsin  (Chapter  XI) ;  Pepsin  (Chapter  VIII) ;  Trypsin  (Chapter  X). 
For  the  application  of  Urease  to  the  determination  of  urea,  see 
Chapters  XVI  and  XXVII. 

1  Anti-pancreatic-protease  or  anti-alkali-protease. 

2  Made  by  dissolving  0.04  gram  of  sodium  carbonate  and  0.015  gram  of  trypsin  in  8 
c.c.  of  water. 


CHAPTER  II 
CARBOHYDRATES 

The  name  carbohydrates  is  given  to  a  class  of  bodies  which  are  an 
especially  prominent  constituent  of  plants  and  which  are  found  also  in 
the  animal  body  either  free  or  as  an  integral  part  of  various  proteins. 
They  are  called  carbohydrates  because  they  contain  the  elements  C,  H 
and  O ;  the  H  and  0  being  present  in  the  proportion  to  form  water.  The 
term  is  not  strictly  appropriate  inasmuch  as  there  are  bodies,  such  as 
acetic  acid,  lactic  acid  and  inositol,  which  have  H  and  O  present  in  the 
proportion  to  form  water,  but  which  are  not  carbohydrates,  and  there 
are  also  true  carbohydrates  which  do  not  have  H  and  O  present  in  this 
proportion,  e.g.j  rhamnose,  CeH^Os. 

Chemically  considered,  the  carbohydrates  are  aldehyde  or  ketone 
derivatives  of  complex  alcohols.  Treated  from  this  standpoint,  the 
aldehyde  derivatives  are  spoken  .of  as  aldoses,  and  the  ketone  deriva- 
tives are  spoken  of  as  ketoses.  The  carbohydrates  are  also  frequently 
named  according  to  the  number  of  oxygen  atoms  present  in  the  mole- 
cule, e.g.,  trioses,  pentoses,  and  hexoses. 

The  more  common  carbohydrates  may  be  classified  as  follows: 

I.  Monosaccharides. 

1.  Pentoses,  C5Hi005. 

(a)  Arabinose. 

(b)  Xylose. 

(c)  Rhamnose  (Methyl-pentose) ,  C6Hi205. 

2.  Hexoses,  CeH^Os. 

^(a)  Glucose. 

(b)  Fructose. 

(c)  Galactose. 

II.  Disaccharides,  Ci2H22On. 

1.  Maltose. 

2.  Lactose. 

3.  Iso-Maltose. 

4.  Sucrose. 

III.  Trisaccharides,  Ci8H32Oi6. 
i.  Rafnnose. 

19 


20  PHYSIOLOGICAL  CHEMISTRY 

IV.  Polysaccharides,  (C6Hi005)  . 

1.  Gum  and  Vegetable  Mucilage  Group. 

(a)  Dextrin. 

(b)  Vegetable  Gums. 

2.  Starch  Group. 

(a)  Starch. 

(b)  Inulin. 

(c)  Glycogen. 

(d)  Lichenin. 

3.  Cellulose  Group. 

(a)  Cellulose. 

(b)  Hemicelluloses. 

(1)  Pentosans. 

Gum  Arabic. 

(2)  Hexosans. 

Galactans. 
M*  Agar-agar. 

Each  member  of  the  above  carbohydrate  classes,  except  the  members 
of  the  pentose  group,  may  be  supposed  to  contain  the  group  CeHioOs, 
called  the  saccharide  group.  The  polysaccharides  consist  of  this  group 
alone  taken  a  large  number  of  times,  whereas  the  disaccharides  may  be 
supposed  to  contain  two  such  groups  plus  a  molecule  of  water,  and  the 
monosaccharides  to  contain  one  such  group  plus  a  molecule  of  water. 
Thus,  (C6Hio05)x  =  polysaccharide,  (C6Hi005)2  +  H20->  disacchar- 
ide,  C6Hio05  +  H2O-»  monosaccharide.  In  a  general  way  the  solu- 
bility of  the  carbohydrates  varies  with  the  number  of  saccharide  groups 
present,  the  substances  containing  the  largest  number  of  these  groups 
being  the  least  soluble.  This  means  simply  that,  as  a  class,  the  mono- 
saccharides (hexoses)  are  the  most  soluble  and  the  polysaccharides 
(starches  and  cellulose)  are  the  least  soluble. 

MONOSACCHARIDES 

Hexoses,  C6Hi2O6 

The  hexoses  are  monosaccharides  containing  six  oxygen  atoms  in  a 
molecule.  They  are  the  most  important  of  the  simple  sugars,  and  two 
of  the  principal  hexoses,  glucose  and  fructose,  occur  widely  distributed 
in  plants  and  fruits.  Of  these  two  hexoses,  glucose  results  from  the 
hydrolysis  of  starch,  whereas  both  glucose  and  fructose  are  formed  in 
the  hydrolysis  of  sucrose.  Galactose,  which  with  glucose  results  from 
the  hydrolysis  of  lactose,  is  also  an  important  hexose.  These  three 
hexoses  are  fermentable  by  yeast,  and  yield  levulinic  acid  upon  heating 


CARBOHYDRATES  21 

with  dilute  mineral  acids.  They  reduce  metallic  oxides  in  alkaline 
solution,  are  optically  active  and  extremely  soluble.  With  phenyl- 
hydrazine  they  form  characteristic  osazones. 

CH2OH 

I 
GLUCOSE  (CHOH)4 

CHO 

Glucose,  also  called  dextrose  or  grape  sugar,  is  present  in  the  blood 
in  small  amount  and  also  occurs  in  traces  in  normal  urine.1  After 
the  ingestion  of  large  amounts  of  glucose,  causing  the  assimilation 
limit  to  be  exceeded,  an  alimentary  glycosuria2  may  arise.  This 
limit  has  been  placed  at  200-250  grams  for  normal  individuals. 
However,  Taylor  and  Hulton3  report  five  cases  in  which  500  grams4 
of  glucose  was  fed  and  sugar  appeared  in  the  urine  in  only  one  in- 
stance. In  the  case  of  starch  and  sucrose  there  also  seems  many 
times  to  be  no  assimilation  limit.  In  other  words  many  normal  indi- 
viduals are  able  to  assimilate  as  much  of  these  carbohydrates  as  they 
can  eat  and  digest.  When  the  sugar-handling  mechanism  is  below 
normal  as  little  as  100  grams  of  glucose  will  cause  hyperglycemia  and 
glycosuria.  In  diabetes  mellitus  very  large  amounts  of  glucose  are 
excreted  in  the  urine.  The  following  structural  formula  nas  been  sug- 
gested by  Victor  Meyer  for  d-glucose: 

CHO 

H— C— OH 
HO— C— H 
H— C— OH 
H— C— OH 

CH2OH 

(For  further  discussion  of  glucose  see  section  on  Hexoses,  page  20.) 

EXPERIMENTS  ON  GLUCOSE 

The  following  tests  are  made  on  glucose  as  a  typical  carbohydrate 
and  are  not  specific  for  this  sugar.  A  specific  test  for  glucose  is.  the 

1See  Folin's  test  for  sugar  in  normal  urine  (Jour.  Biol.  Chcm.t  22,  327,  1915):  also. 
Benedict:  Jour.  Biol.  Chem.,  31,  195,  1918. 

2Benedict  suggests  the  substitution  of  "glycuresis"  for  "glycosuria"  (See  pp.  414,  431) .. 

3Taylor  and  Hulton:  Jour.  Biol.  Chem.,  25,  173,  1916. 

4This  was  the  maximum  amount  that  the  subjects  of  the  tests  could  retain. 


22  PHYSIOLOGICAL    CHEMISTRY 

Phenylhydrazine  Reaction  (3)  in  the  absence  of  a  positive  Resorcinol- 
Hydrochloric  Acid  Reaction  (see  page  35), 

1.  Solubility. — Test  the  solubility  of  glucose  hi  the  "ordinary  solvents"  and 
in  alcohol.     (In  the  solubility  test  throughout  the  book  we  shall  designate  the 
following  solvents  as  the  "ordinary  solvents";  H2O;  10  per  cent  NaCl;  0.5  per 
cent  Na2CO3;  0.2  per  cent  HC1;  concentrated  KOH;  concentrated  HC1.) 

2.  a-Naphthol  Reaction  (Molisch). — Place  approximately  5  c.c.  of  concen- 
trated H2SC>4  in  a  test-tube.    Incline  the  tube  and  slowly  pour  down  the  inner 
side  of  it  approximately  5  c.c.  of  the  sugar  solution  to  which  2  drops  of  Mo- 
lisch's  reagent  (a  15  per  cent  alcoholic  solution  of  a-naphthol)  has  been  added, 
so  that  the  sugar  solution  will  not  mix  with  the  acid.    A  reddish-violet  zone 
is  produced  at  the  point  of  contact. 

The  reaction  is  due  to  the  formation  of  furfural,1 

HC— CH 

II      II 
HC     C-CHO, 

\/ 

o 

by  the  acid.  The  test  is  given  by  all  bodies  containing  a  carbohydrate 
group  and  is  therefore  not  specific  and,  in  consequence,  of  very  little 
practical  importance. 

3.  Phenylhydrazine   Reaction. — Test   according   to   one   of   the   following 
methods :  (a)  To  a  small  amount  of  phenylhydrazine  mixture  (enough  to  fill  the 
rounded  portion  of  a  small  test-tube)  furnished  by  the  instructor,2  add  5  c.c. 
of  the  sugar  solution,  shake  well  and  heat  on  a  boiling  water-bath  for  one-half  to 
three-quarters  of  an  hour.    Allow  the  tube  to  cool  slowly  (not  under  the  tap) 
and  examine  the  crystals  microscopically  (Plate  III,  opposite). 

If  the  solution  has  become  too  concentrated  in  the  boiling  process  it 
will  be  light  red  in  color  and  no  crystals  will  separate  until  it  is  diluted 
with  water. 

Yellow  crystalline  bodies  called  osazones  are  formed  from  certain 
sugars  under  these  conditions,  in  general  each  individual  sugar  giving 
rise  to  an  osazone  of  a  definite  crystalline  form  which  is  typical  for  that 
sugar.  It  is  important  to  remember  in  this  connection  that,  of  the 
simple  sugars  of  interest  in  physiological  chemistry,  glucose  and  fructose 
yield  the  same  osazone.  Each  osazone  has  a  definite  melting-point 
and  as  a  further  and  more  accurate  means  of  identification  it  may  be 

According  to  v.  Ekenstein  and  Blanksma  (Ber.  d.  d.  chem.  GesdL,  43,  2358,  1910), 
oxymethylfurfural  is  formed. 

2  This  mixture  is  prepared  by  combining  2  parts  of  phenylhydrazine  hydrochloride  and 
3  parts  of  sodium  acetate  by  weight.  These  are  thoroughly  mixed  in  a  mortar. 


PLATE  III. 


OSAZONES. 

Upper  form,  dextrosazone;  central  form,  maltosazone;  lower  form,  lactosazone. 


CARBOHYDRATES 


recrystallized  and  identified  by  the  determination  of  its  melting-point 
and  nitrogen  content.  Garard  and  Sherman1  claim  that  "With  the 
best  conditions  it  is  possible  to  detect  5  mg.  of  glucose  in  10  cc.  of 
solution  since  a  distinct  precipitate  is  formed.  If  the  solution  is 
cooled,  i  mg.  gives  a  distinct  precipitate.  If  the  original  solution 
is  neutral  and  comparatively  free  from  other  organic  matter  this 
test  will  show  i  part  of  glucose  in  10,000  of  water  or  i  mg.  in  a 
o.oi  per  cent,  solution.  At  this  dilution  the  precipitate  is  suffi- 
ciently copious,  so  that  there  is  no  question  about  its  presence." 

The  reaction  taking  place  in  the  formation  of  phenylglucosazone  is 
as  follows: 


CH2OH 
(CHOH)  3 
CHOH 

Q 

C 
\H 

Glucose 

CH2OH 

I 
(CHOH)j 

I- 

c=o 


+  C6H5NH-NH2- 


\ 


H 


Phenylhydrazine 

+  C6H6NH-NH2- 
I6  +  C6H5NH2 

Aniline 


NH 


Ammonia 


CH2OH 

(CHOH)  3 

"+  C6H6NH'NH2- 
CHOH 
yN-NHC6H6  +  H2O 

C 
\H 

Phenylhydrazone 

CH2OH 
(CHOH)  3 
C=N-NHC6H6H 


\ 


H 

Glucosazone 


(b)  Place  5  c.c.  of  the  sugar  solution  in  a  test-tube,  add  i  c.c.  of  the  phenyl- 
hydrazine-acetate  solution  furnished  by  the  instructor,2  and  heat  on  a  boiling 
water-bath  for  one-half  to  three-quarters  of  an  hour.  Allow  the  liquid  to  cool 
slowly  and  examine  the  crystals  microscopically  (Plate  III,  opposite  p.  22). 

4.  Diffusibility  of  Glucose.— Test  the  diffusibility  of  glucose  solution  through 
animal  membrane  or  parchment  paper,  making  a  dialyzer  like  one  of  the  models 
shown  in  Fig.  2. 

A  most  satisfactory  dialyzing  bag  may  be  made  of  collodion  as  follows: 
Pour  a  solution  of  collodion  into  a  clean  dry  Erlenmeyer  flask  or  test-tube. 
While  rotating  the  vessel  on  its  longitudinal  axis,  gradually  pour  out  the  collodion, 
at  the  same  time  being  careful  that  the  interior  surface  of  the  flask  is  completely 

1  Garard  and  Sherman:  Jour.  Am.  Chem.  Soc.,  40,  955,  1918. 

2  This  solution  is  prepared  by  mixing  one  part  by  volume,  in  each  case,  of  glacial  acetic 
acid,  one  part  of  water  and  two  parts  of  phenylhydrazine  (the  base). 


24  PHYSIOLOGICAL   CHEMISTRY 

coated  with  the  solution.  Continue  the  rotation  in  the  inverted  position  until 
the  collodion  ceases  to  flow.  After  the  solution  has  evaporated  such  that  the 
collodion  skin  on  the  rim  is  dry  and  stiff,  cut  or  loosen  it  around  the  edge  of  the 
rim.  With  a  pipette  or  wash  bottle  run  in  a  few  cubic  centimeters  of  water  be- 
tween the  membrane  and  the  wall  of  the  flask  or  test-tube.  Shake  the  inclined 
vessel  while  rotating  on  its  longitudinal  axis,  thus  detaching  the  membrane. 
Now  withdraw  the  detached  bag  and  fill  with  water,  to  determine  whether  or  not 
it  contains  defects.1 

All  monosaccharides  and  disaccharides  are  diffusible,  but  many  polysac- 
charides  are  not. 

5.  Influence  of  Alkali  (Moore's  Test).— To  2-3  c.c.  of  sugar  solution  in  a  test- 
tube  add  an  equal  volume  of  concentrated  KOH  or  NaOH,  and  boil.  The  solution 


FIG.  2. — DIALYZING  APPARATUS  FOR  STUDENTS'  USE. 


darkens  and  finally  assumes  a  brown  color.     At  this  point  the  odor  of  caramel 
may  be  detected. 

This  test  is  of  little  practical  value  for  the  detection  of  glucose.  The  alkali 
brings  about  condensation  and  decomposition.  The  brown  color  is  due  to  the 
formation  of  condensation  products.  Among  the  decomposition  products  are  the 
potassium  or  sodium  salts  of  certain  organic  acids. 

6.  Reduction  Tests. — To  their  aldehyde  or  ketone  structure  many 
sugars  owe  the  property  of  readily  reducing  alkaline  solutions  of  the 
oxides  of  metals  like  copper,  bismuth  and  mercury;  they  also  possess 
the  property  of  reducing  ammoniacal  silver  solutions  with  the  separa- 
tion of  metallic  silver.  Upon  this  property  of  reduction  the  most 
widely  used  tests  for  sugars  are  based.  When  whitish-blue  cupric 
hydroxide  in  suspension  in  an  alkaline  liquid  is  heated  it  is  converted 
into  insoluble  black  cupric  oxide,  but  if  a  reducing  agent  like  certain 
sugars  be  present  the  cupric  hydroxide  is  reduced  to  insoluble  yellow 
or  red  cuprous  oxide.  These  changes  are  indicated  as  follows: 

lGies:  Quoted  by  Clark.    Bioch.  Bull.,  i,  198,  1911. 


CARBOHYDRATES  25 

OH 
Cu  -»  Cu  =  0+H2O. 

\  Cupric  oxide 

\  (black). 

OH 

Cupric  hydroxide 
(whitish-blue). 

Reaction  in  absence  of  a  reducing  agent. 

OH 

2Cu  -»  Cu2O+2H2O+O. 

\Cuprous  oxide 
(yellow  to  red). 

OH 

Cupric  hydroxide 

Reaction  in  presence  of  a  reducing  agent. 

The  chemical  equations  here  discussed  are  exemplified  in  Trommer's 
and  Fehling's  tests. 

(a)  Trammer's  Test. — To  5  c.c.  of  sugar  solution  in  a  test-tube  add  one-half  its 
volume  of  KOH  or  NaOH.    Mix  thoroughly  and  add,  drop  by  drop,  a  very  dilute 
solution  of  copper  sulphate.     Continue  the  addition  until  there  is  a  slight  permanent 
precipitate  of  cupric  hydroxide  and  in  consequence  the  solution  is  slightly  turbid. 
Heat,  and  the  cupric  hydroxide  is  reduced  to  yellow  or  brownish-red  cuprous  oxide. 

If  the  solution  of  copper  sulphate  used  is  too  strong  a  small  brownish-red  pre- 
cipitate produced  in  a  weak  sugar  solution  may  be  entirely  masked.  On  the  other 
hand,  particularly  in  testing  for  sugar  in  the  urine,  if  too  little  copper  sulphate  is 
used  a  light-colored  precipitate  formed  by  uric  acid  and  purine  bases  may  obscure 
the  brownish-red  precipitate  of  cuprous  oxide.  The  action  of  KOH  or  NaOH  in  the 
presence  of  an  excess  of  sugar  and  insufficient  copper  will  produce  a  brownish  color. 
Phosphates  of  the  alkaline  earths  may  also  be  precipitated  in  the  alkaline  solution 
and  be  mistaken  for  cuprous  oxide.  Trommer's  test  is  not  very  satisfactory. 

Salkowski1  has  proposed  a  modification  of  the  Trommer  procedure  which  he 
claims  is  a  very  accurate  sugar  test. 

(b)  Fehling's  Test— To  about  i  c.c.  of  Fehling's  solution2  in  a  test-tube  add 
about  4  c.c.  of  water,  and  boil.3    [The  cupric  hydroxide  is  held  in  solution  by  the 
sodium  potassium  tartrate  (Rochelle  salt).]    This  is  done  to  determine  whether 
the  solution  will  of  itself  cause  the  formation  of  a  precipitate  of  brownish-red 
cuprous  oxide.    If  such  a  precipitate  forms,  the  Fehling's  solution  must  not  be 
used.    Add  sugar  solution  to  the  warm  Fehling's  solution  a  few  drops  at  a 
time  and  heat  the  mixture  after  each  addition.    The  production  of  yellow 
or  brownish-red   cuprous   oxide  indicates   that  reduction  has   taken  place. 
The  yellowish  precipitate  is  more  likely  to  occur  if  the  sugar  solution  is  added 

1  Salkowski:  Zeit.  physiol.  Chem.,  79,  164,  1912. 

2  Fehling's  solution  is  composed  of  two  definite  solutions — a  copper  sulphate  solution 
and  an  alkaline  tartrate  solution — which  may  be  prepared  as  follows: 

Copper  sulphate  solution  =  34.65  grams  of  copper  sulphate  dissolved  in  water  and  made 
up  to  500  c.c. 

Alkaline  tartrate  solution  =  125  grams  of  potassium  hydroxide  and  173  grams  of  Rochelle 
salt  dissolved  in  water  and  made  up  to  500  c.c. 

These  solutions  should  be  preserved  separately  in  rubber-stoppered  bottles  and  mixed 
in  equal  volumes  when  needed  for  use.  This  is  done  to  prevent  deterioration. 

3  More  dilute  Fehling's  solution  should  be  used  in  testing  very  dilute  sugar  solutions. 
In  case  of  concentrated  sugar  solutions  it  may  sometimes  be  desirable  to  use  a  larger  volume 
of  the  Fehling's  solution. 


26  PHYSIOLOGICAL   CHEMISTRY 

rapidly  and  in  large  amount,  whereas  with  a  less  rapid  addition  of  smaller 
amounts  of  sugar  solution  the  brownish-red  precipitate  is  generally  formed. 
The  differences  in  color  of  the  cuprous  oxide  precipitates  under  different  con- 
ditions are  apparently  due  to  differences  in  the  size  of  the  particles,  the  more 
finely  divided  precipitates  having  a  yellow  color,  while  the  coarser  ones  are  red. 
In  the  presence  of  protective  colloidal  substances  the  yellow  precipitate  is 
usually  formed.1 

This  is  a  much  more  satisfactory  test  than  Trommer's,  but  even  this 
test  is  not  entirely  reliable  when  used  to  detect  sugar  in  the  urine.  Such 
bodies  as  conjugate  glycuronates,  uric  acid,  nulceoprotein,  and  homogen- 
tisic  acid  when  present  in  sufficient  amount  may  produce  a  result  simi- 
lar to  that  produced  by  sugar.  Phosphates  of  the  alkaline  earths  may 
be  precipitated  by  the  alkali  of  the  Fehling's  solution  and  in  appearance 
may  be  mistaken  for  cuprous  oxide.  Cupric  hydroxide  may  also 
be  reduced  to  cuprous  oxide  and  this  in  turn  be  dissolved  by  creatinine, 
a  normal  urinary  constituent.  This  will  give  the  urine  under  examina- 
tion a  greenish  tinge  and  may  obscure  the  sugar  reaction  even  when  a 
considerable  amount  of  sugar  is  present.  According  to  Laird,2  even 
small  amounts  of  creatinine  will  retard  the  reaction  velocity  of  reducing 
sugars  with  Fehling's  solution. 

In  testing  urine  preserved  by  chloroform  a  positive  test  may  be  ob- 
tained in  the  absence  of  sugar.  This  is  due  to  the  fact  that  the  hot 
alkali  produces  formic  acid  (a  reducing  fatty  acid)  from  the  chloroform. 

Ammonium  salts  also  interfere  with  Fehling's  test.  If  present  in 
excess  the  solution  (e.g.,  urine)  should  be  made  alkaline  and  boiled  in 
order  to  decompose  the  ammonium  salts. 

If  the  solution  under  examination  by  Fehling's  test  is  acid  in  reaction 
it  must  be  neutralized  or  made  alkaline  before  applying  the  test. 

(c)  Benedict's  Test.3 — Benedict  has  modified  the  Fehling  solution  and  has 
succeeded  in  obtaining  one  which  does  not  deteriorate  upon  long  standing.4 
The  following  is  the  procedure  for  the  detection  of  glucose  in  solution.  To  5  c.c. 
of  the  reagent  in  a  test-tube  add  8  (not  more)  drops  of  the  solution  under  exami- 

1  Fischer  and  Hooker:  Science,  N.  S.,  45,  505,  1917. 

'Laird:  Journal  of  Pathology  and  Bacteriology,  16,  398,  1912. 

3 Benedict:  Jour.  'Biol.  Chem.,  5,  485,  1909:  Jour.  Am.  Med.  Ass'n,  57,  1193,  1911. 

4  Benedict's  solution  has  the  following  composition: 

Copper  sulphate 17  •  3  grams. 

Sodium  citrate 173 -o  grams. 

Sodium  carbonate  (anhydrous) 100 .  o  grams. 

Distilled  water  to  make  i  liter. 

With  the  aid  of  heat  dissolve  the  sodium  citrate  and  carbonate  in  about  800  c.c.  of  water. 
Pour  (through  a  folded  filter  paper  if  necessary)  into  a  glass  graduate  and  make  up  to  850 
c.c.  Dissolve  the  copper  sulphate  in  about  100  c.c.  of  water.  Pour  the  carbonate-citrate 
solution  into  a  large  beaker  or  casserole  and  add  the  copper  sulphate  solution  slowly,  with 
constant  stirring  and  make  up  to  one  liter.  The  mixed  solution  is  ready  for  use  and  does 
not  deteriorate  upon  long  standing. 


CARBOHYDRATES  27 

nation.  Boil  the  mixture  vigorously  for  two  minutes  and  then  allow  the  fluid 
to  cool  spontaneously  (Do  not  hasten  cooling  by  immersion  in  cold  water). 
In  the  presence  of  dextrose  the  entire  body  of  the  solution  will  be  filled  with  a 
colloidal  precipitate,  which  may  be  red,  yellow  or  green  in  color,  depending 
upon  the  amount  of  sugar  present.  In  the  presence  of  over  0.2-0.3  per  cent 
of  glucose  the  precipitate  will  form  quickly.  If  no  glucose  is  present,  the  solution 
will  remain  perfectly  clear.  (If  urine  is  being  tested,  it  may  show  a  very  faint 
turbidity,  due  to  precipitated  urates.) 

Even  very  small  quantities  of  glucose  (o.i  per  cent)  yield  precipi- 
tates of  surprising  bulk  with  this  reagent,  and  the  positive  reaction  for 
glucose  is  the  filling  of  the  entire  body  of  the  solution  with  a  precipitate, 
so  that  the  solution  becomes  opaque.  Since  amount  rather  than  color  of 
the  precipitate  is  made  the  basis  of  this  test,  it  may  be  applied  even  for 
the  detection  of  small  quantities  of  glucose,  as  readily  in  artificial  light  as 
in  daylight.  Chloroform  does  not  interfere  with  this  test  nor  do  uric  acid 
or  creatinine  interfere  to  such  an  extent  as  in  the  case  of  Fehling's  test. 

(d)  Folin-McEllroy  Test.1 — To  5  c.c.  of  the  reagent2  in  a  test  tube  add 
5-8  drops  of  urine  (never  add  more  than  0.5  c.c.)  and  boil  for  1-2  minutes  or 
heat  in  a  beaker  of  boiling  water  for  3  minutes.    If  more  than  the  normal  traces 
of  sugar  be  present  the  hot  solution  will  be  filled  with  a  colloidal  (greenish- 
yellow  or  reddish)  precipitate  as  in  Benedict's  test.    Because  of  the  sensitiveness 
of  this  test,  when  working  with  urine  only  a  distinctly  positive  test  obtained  with 
the  solution  still  hot  is  to  be  regarded  as  positive. 

(e)  Bismuth  Reduction  Test  (Nylander). — To  5  c.c.  of  sugar  solution  in  a  test- 
tube  add  one-tenth  its  volume  of  Nylander's  reagent3  and  heat  for  five  minutes 
in  a  boiling  water-bath.4    The  solution  will  darken  if  reducing «ugaris^>resent, 
and  upon  standing  for  a  few  moments  a  black  color  will  appear. 

This  color  is  due  to  the  precipitation  of  bismuth.  If  the  test  is  made 
on  urine  containing  albumin  this  must  be  removed,  by  boiling  and 
filtering,  before  applying  the  test,  since  with  albumin  a  similar  change  of 
color  is  produced.  Glucose  when  present  to  the  extent  of  0.08  per  cent 
may  be  easily  detected  by  this  reaction  (Rabe6  claims  that  o.oi  per  cent 
sugar  may  be  so  detected).  Uric  acid  and  creatinine  which  interfere 

1  Folin  and  McEllroy:  Jour.  BioL  Chem.,  33,  513,  1918. 

2  Folin-McEllroy  Reagent. — It  has  been  shown  that  alkaline  phosphates  may  be  used 
in  [place  of  tartrates  or  citrates  to  hold  cupric  hydroxide  in  solution.     This  reagent  is 
based  on  that  principle.     Dissolve  100  g.  of  sodium  pyrophosphate,  30  g.  of  disodium  phos- 
phate and  50  g.  of  dry  sodium  carbonate  in  approximately  i  liter  of  water  by  the  aid  of 
a  little  heat.     Dissolve  separately  13  g.  of  copper  sulphate  in  about  200  c.c.  of  water. 
Pour  the  copper  sulphate  solution  into  the  phosphate-carbonate  solution  and  shake. 

3  Nylander's  reagent  is  prepared  by  digesting  2  grams  of  bismuth  subnitrate  and  4  grams 
of  Rochelle  salt  in  100  c.c.  of  a  10  per  cent  potassium  hydroxide  solution.    The  reagent  is 
then  cooled  and  filtered. 

4  Hammarsten  suggests  that  the  mixture  should  be  boiled  2-5  minutes  (according  to  the 
sugar  content)  over  a  free  flame  and  the  tube  then  permitted  to  stand  5  minutes  before 
drawing  conclusions. 

6  Rabe:  Apoth.  Ztg.,  29,  554,  1914. 


28  PHYSIOLOGICAL  CHEMISTRY 

with  the  Fehling's  test  do  not  interfere  with  the  Nylander  test.  It 
is  claimed  by  Bechold  that  the  bismuth  reduction  tests  give  a  negative 
reaction  with  solutions  containing  sugar  when  mercuric  chloride  or 
chloroform  is  present.  Other  observers1  have  failed  to  verify  the 
inhibitory  action  of  mercuric  chloride  and  have  shown  that  the  in- 
hibitory influence  of  chloroform  may  be  overcome  by  raising  the  tem- 
perature of  the  urine  to  the  boiling-point  for  a  period  of  five  minutes 
previous  to  making  the  test.  Urines  rich  in  indican,  urochrome,  uroery- 
thrin  or  hematoporphyrin,  as  well  as  urines  excreted  after  the  ingestion  of 
large  amounts  of  certain  medicinal  substances,  may  give  a  darkening  of 
Nylander 's  reagent  similar  to  that  of  a  true  sugar  reaction.  It  is  a  dis- 
puted point  whether  the  urine  after  the  administration  of  urotropin 
will  reduce  Nylander 's  reagent.2  Strausz3  has  recently  shown  that  the 
urine  of  diabetics  to  whom  "lothion"  (diiodohydroxypropane)  has 
been  administered  will  give  a  negative  Nylander-Almen  reaction  and 
respond  positively  to  the  Fehling  and  polariscopic  tests.  " lothion" 
also  interferes  with  the  Nylander-Almen  test  in  vitro  whereas  KI  and 
I  do  not. 

According  to  Rustin  and  Otto,  the  addition  of  PtCl2  increases  the 
delicacy  of  Nylander-Almen  reaction.  They  claim  that  this  procedure 
causes  the  sugar  to  be  converted  quantitatively.  No  quantitative 
method  has  yet  been  devised,  however,  based  upon  this  principle. 

Bohmansson4  before  testing  the  urine  under  examination  treats 
it  (10  c.c.)  with  J^  volume  of  25  per  cent  hydrochloric  acid  and  about 
J^  volume  of  boneblack.  This  mixture  is  shaken  one  minute,  then 
filtered  and  the  neutralized  filtrate  tested  by  Nylander-Almen  reaction. 
Bohmansson  claims  that  this  procedure  removes  certain  interfering 
substances,  in  particular  urochrome. 

A  positive  bismuth  reduction  test  is  probably  due  to  the  following 
reactions: 

(a)  Bi(OH)2NO3  +  KOH-»Bi(OH)3  +  KN03. 

(b)  2Bi(OH)3-30  -»  Bi2  +  3H20. 

(f )  Indigo  Carmine  Test. — Place  in  a  test  tube  2  c.c.  of  water  with  an  in- 
digo sodium-carbonate  tablet  and  one  sodium  carbonate  tablet.5 

Heat  the  tube  gently  until  the  indigo  is  dissolved.    Add  to  the  blue  solution, 

1Rehfuss  and  Hawk:  Journal  of  Biological  Chemistry;  7,  267,  1910;  also  Zeidlitz: 
Upsala  Lakareforen  Fork.,  N.  F.,  n,  1906. 

2Abt:  Archives  of  Pediatrics,  24,  275,  1907;  also  Weitbrecht:  Schweiz.  Wochschr.,  47, 
577,  1909. 

'Strausz:  Munch,  med.  Wcoh,.  59  85,  1912. 

4  Bohmansson :  Biochem.  Zeit.,  19,  p.  281. 

5  These  tablets  may  be  obtained  from  Parke,  Davis  &  Company. 


CARBOHYDRATES  2  9 

from  a  pipette,  one  drop  of  the  solution  to  be  tested,  and  keep  the  fluid  at  the 
boiling  point  for  sixty  seconds,  without,  however,  permitting  active  boiling. 

If  no  change  is  produced  add  a  second  drop  of  the  solution,  and  heat  once 
more.  If  any  notable  quantity  of  sugar  is  present,  the  fluid  will  be  observed  to 
change  from  pure  blue  to  violet,  then  to  purple  and  red,  and  in  extreme  cases 
will  fade  to  a  pale  yellow.  If  there  is  only  a  trace  of  sugar,  the  color  will  merely 
change  to  one  of  the  intermediate  shades. 

Care  should  be  exercised  to  prevent  agitation  or  boiling  of  the  liquid  during 
this  test.  Contact  with  oxygen  of  the  air  from  boiling  or  agitation  prevents  the 
discharge  of  the  blue  color. 

(g)  Barfoed's  Test.  —  Place  about  5  c.c.  of  Barfoed's  solution1  hi  a  test-tube 
and  heat  to  boiling.  Add  glucose  solution  slowly,  a  few  drops  at  a  time,  heating 
after  each  addition.  Reduction  is  indicated  by  the  formation  of  a  red  precipitate 
of  cuprous  oxide.  If  the  precipitate  does  not  form  after  boiling  one-half  minute2 
allow  the  tube  to  stand  a  few  minutes  and  examine. 

According  to  Welker3  chlorides  interfere  spronouncedly  with  the 
reaction  causing  the  formation  of  a  green  precipitate. 

Barfoed's  test  is  not  a  specific  test  for  glucose  as  is  frequently  stated, 
but  simply  serves  to  detect  monosaccharides.  Disaccharides  will  also 
respond  to  the  test,  under  proper  conditions  of  acidity.4  Also  if  the 
sugar  solution  is  boiled  sufficiently  long,  in  contact  with  the  reagent,  to 
hydrolyze  the  disaccharide  through  the  action  of  the  acetic  acid  present 
in  the  Barfoed's  solution  a  positive  test  results.5  Barfoed's  is  a  copper 
reduction  test,  but  differs  from  Fehling's  and  other  reduction  tests  in 
that  the  reduction  is  brought  about  in  an  acid  solution.  It  is  unsuited 
for  the  detection  of  sugar  in  urine. 

(h)  Picric  Acid  Test.  —  To  5  c.c.  of  the  sugar  solution  add  2-3  c.c.  of  saturated 
picric  acid  solution  and  about  i  c.c.  of  10  per  cent  KOH.  Warm.  Note  the 
development  of  a  mahogany  red  color  in  the  presence  of  glucose  due  to 
reduction  of  the  picric  acid  with  the  formation  of  picramic  acid  : 


OH(NO2)3  ->  CeH2  OH  NH2(NO2)2 

Picric  Acid  Picramic  Acid 

This  test  has  been  made  the  basis  of  a  method  for  the  colorimetric  determina- 
tion of  sugar  in  blood.  See  Chapter  XVI. 

7.  Alcoholic  Fermentation.  —  Prepare  500  c.c.  of  a  concentrated  (10  per  cent) 
solution  of  glucose,  add  a  small  amount  of  egg  albumin  or  commercial  peptone 
and  introduce  the  mixture  into  a  liter  flask.  Add  yeast,  and  by  means  of  a  bent 

1  Barfoed's  solution  is  prepared  as  follows:  Dissolve  9  grams  of  neutral  crystallized 
cppper^acetate  in  100  c.c.  of  water  and  add  1.2  c.c.  of  50  per  cent  acetic  acid.    This  solu- 
tion should  be  freshly  made. 

2  Blake:  Jour.  Am.  Chem.  Soc.,  38,  1245,  1916. 

3  Welker:  Jour.  Am.  Chem.  Soc.,  37,  2227,  1915. 
4Mathews  and  McGuigan:  Am.  Jour.  PhysioL,  19,  175,  1907. 
6Hinkle  and  Sherman:  Jour.  Am.  Chem.  Soc.,  29,  1744,  1907 


PHYSIOLOGICAL  CHEMISTRY 


tube  connect  this  flask  with  a  second  flask  containing  a  solution  of  barium 
hydroxide  protected  from  the  air  by  a  soda  lime  tube  in  the  stopper  (see  Fig.  3). 

Place  the  flasks  in  a  warm  place  and  note  the 
passage  of  gas  bubbles  into  the  barium  hydroxide 
solution.  As  these  gas  bubbles  (CO2)  enter,  a 
white  precipitate  of  barium  carbonate  will  form. 
The  glucose  has  been  fermented  according  to  the 
following  equation: 


FIG.  3. — FERMENTATION 
APPARATUS. 


FIG.  4. — IODOFORM.  (Autenrieth .) 


2<X>2 

When  the  activity  of  the  yeast  has  practically  ceased  decant  the  supernatant 
fluid,  return  it  to  the  cleaned  flask,  connect  with  a  condenser  and  distil.  Catch 
the  first  portion  of  the  distillate,  which  may  be  redistilled  if  its  alcohol  content 
is  low,  and  test  for  alcohol  by  one  of  the  following  re- 
actions : 

(a)  lodoform  Test.— Render  2-3  c.c.  of  the  distillate 
alkaline  with  potassium  hydroxide  solution  and  add  a 
few  drops  of  iodine  solution.    Heat  gently  and  note 
the  formation  of  iodoform  crystals.    Examine  these 
crystals  under  the  microscope  and  compare  them  with 
those  hi  Fig.  4. 

(b)  Aldehyde  Test.— Place  5  c.c.  of  the  distillate 
in  a  test-tube,  add  a  few  drops  of  potassium  dichro- 
mate  solution,  K2Cr2O7,  and  render  it  acid  with  dilute 
sulphuric  acid.    Boil  the  acid  solution  and  note  the 
odor  of  aldehyde  changing  to  that  of  acetic  acid. 

8.  Fermentation  Test— "Rub  up"  in  a  mortar 
about  20  c.c.  of  the  sugar  solution  with  a  small  piece 
of  compressed  yeast.  Transfer  the  mixture  to  a  sac- 
charometer  (shown  in  Fig.  5)  and  stand  it  aside  in  a 
warm  place  for  about  twelve  hours.  If  the  sugar  is 
fermentable,  alcoholic  fermentation  will  occur  and  car- 
bon dioxide  will  collect  as  a  gas  in  the  upper  portion  of 
the  tube.  On  the  completion  of  fermentation  introduce 
a  little  potassium  hydroxide  solution  into  the  graduated 

portion  by  means  of  a  bent  pipette,  fill  the  bulb  portion  with  water,  place  the 
thumb  tightly  over  the  opening  in  the  apparatus  and  invert  the  saccharometer. 


FIG.  5. — EiNHORNj  SAC- 
CHAROMETER. 


CARBOHYDRATES  31 

Remembering  that  KOH  has  the  power  to  absorb  CO  2  how  do  you  explain  the 
result?1  Filter  some  of  the  mixture.  To  5  c.c.  of  the  filtrate  add  several  drops 
of  a  solution  of  iodine  in  potassium  iodide  (enough  to  give  a  yellow  color  to  the 
whole  mixture).  Warm  gently.  Note  iodoform  odor  and  examine  under 
microscope  for  crystals  of  iodoform  (see  Fig.  4).  What  does  a  positive  test 
here  indicate? 

9.  Formation   of   Caramel. — Gently  heat  a  small  amount  of  pulverized  glu- 
cose in  a  test-tube.     After  the  sugar  has  melted  and  turned  brown,  allow  the 
tube  to  cool,  add  water  and  warm.    The  coloring  matter  produced  is  known  as 
caramel. 

10.  Demonstration  of  Optical  Activity. —  A  demonstration  of  the  use  of  the 
polariscope,  by  the  instructor,  each  student  being  required  to  take  readings  and 
compute  the  "specific  rotation." 

USE  OF  THE  POLARISCOPE 

For  a  detailed  description  of  the  different  forms  of  polariscopes,  the 
method  of  manipulation  and  the  principles  involved,  the  student  is 
referred  to  any  standard  text-book  of  physics.  A  brief  description  fol- 


FIG.  6. — ONE  FORM  or  LAURENT  POLARISCOPE. 

Bt  Microscope  for  reading  the  scale;  C,  a  vernier;  E,  position  of  the  analyzing^Nicol  prism; 
H,  polarizing  Nicol  prism  in  the  tube  below  this  point. 

lows.  An  ordinary  ray  of  light  vibrates  in  every  direction.  If  such  a 
ray  is  caused  to  pass  through  a  "polarizing"  Nicol  prism  it  is  resolved 
into  two  rays,  one  of  which  vibrates  in  every  direction  as  before  and  a 
second  ray  which  vibrates  in  one  plane  only.  This  latter  ray  is  said  to 
be  polarized.  Many  organic  substances  (sugar,  proteins,  etc.)  have  the 
power  of  twisting  or  rotating  this  plane  of  polarized  light,  the  extent  to 
which  the  plane  is  rotated  depending  upon  the  number  of  molecules 

1The  findings  of  Neuberg  and  associates2  indicate  that  the  liberation  of  carbon  di- 
oxide by  yeast  is  not  necessarily  a  criterion  of  the  presence  of  sugar.  The  presence  of 
an  enzyme,  called  carboxylase,  has  been  demonstrated  in  yeast  which  has  the  power  of 
splitting  off  CO*  from  the  carboxyl  group  of  amino-  and  other  aliphatic  acids. 

J Neuberg  and  Associates:  Biochem.  Zeitsch.,  31,  170;  32,  323;  36,  (60,  68,  76),  1911. 


32  ,  PHYSIOLOGICAL  CHEMISTRY 

which  the  polarized  light  passes.  Substances  which  possess  this  power 
are  said  to  be  "optically  active."  The  specific  rotation  of  a  substance  is 
the  rotation  expressed  in  degrees  which  is  afforded  by  i  gram  of  sub- 
stance dissolved  in  i  c.c.  of  water  in  a  tube  one  decimeter  in  length. 
The  specific  rotation,  (ct)D,  may  be  calculated  by  means  of  the  following 
formula  : 


in  which 

D  =  sodium  light. 

a  =  observed  rotation  in  degrees. 

p  =  grams  of  substance  dissolved  in  i  c.c.  of  liquid.] 

/  =  length  of  the  tube  in  decimeters. 

If  the  specific  rotation  has  been  determined  and  it  is  desired  to  ascer- 
tain the  per  cent  of  the  substance  in  solution,  this  may  be  obtained  by 
the  use  of  the  following  formula, 


The  value  of  p  multiplied  by  100  will  be  the  percentage  of  the  substance 
in  solution. 

SPECIFIC  ROTATIONS  OF  MORE  COMMON  CARBOHYDRATES1 


d-  Glucose 

-1-     S2    $° 

Sucrose  

+    66.5° 

(f-Fructose 

—     02    3° 

Lactose                                       .  .  . 

+    52  5° 

d-Galactose 

+     8l    <)° 

Maltose  

+  137.0° 

d-M!annose 

4-     Id.    2° 

Raffinose                            

-(-  104  o° 

J-Arabinose 

+  104  5° 

Dextrin  

+  10^.0° 

/-Xylose  

+IQ.O° 

Starch  (soluble)  

+  196.0° 

Rhamnose. 

+      00° 

Glycogen  

+  197.0° 

An  instrument  by  means  of  which  the  extent  of  the  rotation  may  be 
determined  is  called  a  polariscope  or  poldrimeter.  Such  an  instrument 
designed  especially  for  the  examination  of  sugar  solutions  is  termed  a 
saccharimeter  or  polarizing  saccharimeter .  The  form  of  polariscope  in 
Fig.  6,  page  31,  consists  essentially  of  a  long  barrel  provided  with  a 
Nicol  prism  at  either  end  (Fig.  7) .  The  solution  under  examination  is 
contained  in  a  tube  which  is  placed  between  these  two  prisms.  At. 
the  front  end  of  the  instrument  is  an  adjusting  eyepiece  for  focusing 
and  a  large  recording  disc  which  registers  in  degrees  and  fractions  of  a 

1  The  specific  rotation  varies  with  the  temperature  and  concentration  of  the  solution. 
The  figures  here  given  are  for  concentrations  of  about  10  per  cent  and  temperatures  of  about 
2o°C.  Fresh  solutions  may  give  markedly  different  values  due  to  mutarotation,  the  figures 
here  given  representing  the  constant  values  obtained  on  standing. 


CARBOHYDRATES 


33 


degree.  The  light  is  admitted  into  the  far  end  of  the  instrument  and  is 
polarized  by  passing  through  a  Nicol  prism.  This  polarized  ray  then 
traverses  the  coluirm  of  liquid  within  the  tube  mentioned  above  and 
if  the  substance  is  optically  active  the  plane  of  the  polarized  ray  is 


FIG.  7. — DIAGRAMMATIC  REPRESENTATION  OF  THE  COURSE  OF  THE  LIGHT  THROUGH  THE 

LAURENT  POLARISCOPE.     (The  direction  is  reversed  from  that  of  Fig.  6,  p.  31.) 
a,  Bichromate  plate  to  purify  the  light;  b,  the  polarizing  Nicol  prism;  c,  a  thin  quartz 
plate  covering  one-half  the  field  and  essential  in  producing  a  second  polarized  plane;  dt 
tube  to  contain  the  liquid  under  examination;  e,  the  analyzing  Nicol  prism;/  and  g,  ocular 
lenses. 

rotated  to  the  right  or  left.     Bodies  rotating  the  ray  to  the  right  are 
called  dexro-rotatory  and  those  rotating  it  to  the  left  lew-rotatory. 

Within  the  apparatus  is  a  disc  which  is  so  arranged  as  to  be  without 
lines  and  uniformly  light  at  zero.     Upon  placing  the  optically  active 


FIG.  8. — POLARISCOPE  (SCHMIDT  AND  HANSCH  MODEL). 

substance  in  position,  however,  the  plane  of  polarized  light  is  rotated 
or  turned  and  it  is  necessary  to  rotate  the  disc  through  a  certain  number 
of  degrees  in  order  to  secure  the  normal  conditions,  i.e., "  without  lines 

3 


34  PHYSIOLOGICAL  CHEMISTRY 

and  uniformly  light."  The  difference  between  this  reading  and  the 
zero  is  a  or  the  observed  rotation  in  degrees. 

Sugar  solutions  (glucose,  levulose,  lactose,  maltose,  but  not  sucrose) 
when  freshly  prepared  possess  a  changing  rotation,  so  called  mutarotation. 
For  this  reason  such  solutions  before  polariscopic  examination  should 
be  allowed  to  stand  over  night,  heated  to  ioo°C.  and  then  cooled,  or 
treated  with  a  drop  of  ammonia  followed  by  a  drop  of  acid. 

Polarizing  saccharimeters  are  also  constructed  by  which  the  per- 
centage of  sugar  in  solution  is  determined  by  making  an  observation 
and  multiplying  the  value  of  each  division  on  a  horizontal  sliding  scale 
by  the  value  of  the  division  expressed  in  terms  of  dextrose.  This 
factor  may  vary  according  to  the  instrument. 

"Optical"  methods  embracing  the  determination  of  the  optical 
activity  are  being  utilized  in  recent  years  in  many  "quantitative" 
connections. l 

CH2OH 

I 
FRUCTOSE  (CHOH)3 

CO 

:H2OH 

As  already  stated,  fructose,  sometimes  called  levulose  or  fruit  sugar, 
occurs  widely  disseminated  throughout  the  plant  kingdom  in  company 
with  glucose.  Although  it  is  a  ketose  it  nevertheless  reduces  metallic 
oxides  in  alkaline  solution  due  to  the  presence  of  the  terminal  group 
CO  CH^OH.  For  the  same  reason  monohydroxyacetone  (CH3  CO-- 
CH2OH)  also  reduces  such  solutions  although  acetone  (CHS  CO  CHs) 
does  not.  The  reducing  power  of  fructose  is  somewhat  weaker  than 
that  of  dextrose.  Fructose  does  not  ordinarily  occur  in  the  urine  in 
diabetes  mellitus,  but  has  been  found  in  exceptional  cases.  With 
phenylhydrazine  it  forms  the  same  osazone  as  glucose.  With  me  thy  1- 
phenylhydrazine,  levulose  forms  a  characteristic  methylphenylfruc- 
tosazone. 

(For  a  further  discussion  of  fructose  see  the  section  on  Hexoses, 
page  20.) 

EXPERIMENTS  ON  FRUCTOSE 

1-6.  Repeat  Solubility,  Fehling's,  Phenylhydrazine,  Barfoed's,  Nylander's, 
and  Fermentation  tests  as  given  under  Glucose,  pages  21-32. 

Abderhalden  and  Schmidt:  "Determination  of  blood  content  by  means  of  the  optical 
method,"  Zeit.  physiol.  Chem.,  66,  120,  1910;  also  C.  Neuberg:  "Determination  of  nucleic 
acid  cleavage  by  polarization,"  Biochemische  Zeitschrift,  30,  505,  1911. 


CARBOHYDRATES  35 

7»  Resorcinol-Hydrochloric  Acid  Reaction  (Seliwanoff). — To  5  c.c.  of  Seli- 
wanofPs  reagent1  in  a  test-tube  add  a  few  drops  of  a  fructose  solution  and  heat  the 
mixture  to  boiling.  A  positive  reaction  is  indicated  by  the  production  of  a  red 
color  and  the  separation  of  a  brown-red  precipitate.  The  latter  may  be  dissolved 
in  alcohol  to  which  it  will  impart  a  striking  red  color. 

If  the  boiling  be  prolonged  a  similar  reaction  may  be  obtained  with 
solutions  of  glucose  or  maltose.  This  has  been  explained2  in  the  case 
of  glucose  as  due  to  the  transformation  of  the  glucose  into  fructose  by 
the  catalytic  action  of  the  hydrochloric  acid.  The  precautions  neces- 
sary for  a  positive  test  for  levulose  are  as  follows:  The  concentration 
of  the  hydrochloric  acid  must  not  be  more  than  12  per  cent.  The  reac- 
tion (red  color)  and  the  precipitate  must  be  observed  after  not  more 
than  20-30  seconds  boiling.  Glucose  must  not  be  present  in  amounts 
exceeding  2  per  cent.  The  precipitate  must  be  soluble  in  alcohol  with 
a  bright  red  color. 

8.  Borchardfs  Reaction. — To  about  5  c.c.  of  a  solution  of  fructose  in  a  test- 
tube  add  an  equal  volume  of  25  per  cent  hydrochloric  acid  and  a  few  crystals  of 
resorcinol.    Heat  to  boiling  and  after  the  production  of  a  red  color,  cool  the  tube 
under  running  water  and  transfer  to  an  evaporating  dish  or  beaker.     Make  the 
mixture  slightly  alkaline  with  solid  potassium  hydroxide,  return  it  to  a  test-tube, 
add  2-3  c.c.  of  acetic  ether  and  shake  the  tube  vigorously.    In  the  presence  of 
levulose,  the  acetic  ether  is  colored  yellow.     (For  further  discussion  of  the  test  see 
Chapter  XXIV.) 

9.  Formation  of  Methylphenylfructosazone. — To  a  solution  of  1.8  grams  of 
levulose  in  10  c.c.  of  water  add  4  grams3  of  methylphenylhydrazine  and  enough 
alcohol  to  clarify  the  solution.    Introduce  4  c.c.  of  50  per  cent  acetic  acid  and  heat 
the  mixture  for  5-10  minutes  on  a  boiling  water-bath.4     On  standing  15  minutes 
at  room  temperature,  crystallization  begins  and  is  complete  in  two  hours.     By 
scratching  the  sides  of  the  flask  or  by  inoculation,  the  solution  quickly  congeals  to 
form  a  thick  paste  of  reddish-yellow  silky  needles.     These  are  the  crystals  of  methyl- 
phenylfructosazone.     They  may  be  recrystallized  from  hot  95  per  cent  alcohol  and 
melt  at  iS3°C. 

CH2OH 
I 

GALACTOSE,  (CHOH)4' 

CHO 

Galactose  occurs  with  glucose  as  one  of  the  products  of  the  hydro- 
lysis of  lactose.  It  is  dextro-rotatory,  forms  an  osazone  with  phenyl- 
hydrazine  and  ferments  slowly  with  yeast.  Upon  oxidation  with  nitric 
acid  galactose  yields  mucic  acid,  thus  differentiating  this  monosac- 
charide  from  glucose  and  fructose.  Lactose  also  yields  mucic  acid 
under  these  conditions.  The  mucic  acid  test  may  be  used  in  urine 

1  Seliwanoff  s  reagent  may  be  prepared  by  dissolving  0.05  gram  of  resorcinol  in  100  c.c. 
of  dilute  (1:2)  hydrochloric  acid. 

2Koenigsfeld:  Bioch.  ZeiL,  38,  311,  1912. 
3  3.66  grams  if  absolutely  pure. 
4 Longer  heating  is  to  be  avoided. 


36  PHYSIOLOGICAL   CHEMISTRY 

examination  to  differentiate  lactose  and  galactose  from  other  reducing 
sugars. 

EXPERIMENTS  ON  GALACTOSE 

1 .  Phloroglucinol-Hydrochloric  Acid  Reaction  (Tollens) . — To  equal  volumes  of 
galactose  solution  and  hydrochloric  acid  (sp.  gr.  1.09)  add  a  little  phloroglucinol, 
and  heat  the  mixture  on  a  boiling  water-bath.     Galactose,  pentose  and  glycuronic 
acid  will  be  indicated  by  the  appearance  of  a  red  color.     Galactose  may  be 
differentiated  from  the  two  latter  substances  in  that  its  solutions  exhibit  no 
absorption  bands  upon  spectroscopical  examination. 

2.  Mucic  Acid  Test. — Treat  100  c.c.  of  the  solution  containing  galactose  with 
20  c.c.  of  concentrated  nitric  acid  (sp.  gr.  1.4)  and  evaporate  the  mixture  hi  a  broad, 
shallow  glass  vessel  on  a  boiling  water-bath  until  the  volume  of  the  mixture  has 
been  reduced  to  about  20  c.c.    At  this  point  the  fluid  should  be  clear,  and  a  fine 
white  precipitate  of  mucic  acid  should  form. 

If  the  percentage  of  galactose  present  is  low  it  may  be  necessary  to 
cool  the  solution  and  permit  it  to  stand  for  some  time  before  the 
precipitate  will  form.  It  is  impossible  to  differentiate  between  galactose 
and  lactose  by  this  test,  but  the  reaction  serves  to  differentiate  these 
two  sugars  from  all  other  reducing  sugars.  Differentiate  lactose  from 
galactose  by  means  of  Barfoed's  test  (page  29). 

3.  Phenylhydrazine  Reaction. — Make  the  test  according  to  directions  given 
under  Glucose,  3,  page  22. 

Pentoses,  C5Hi005 

In  plants,  and  more  particularly  in  certain  gums,  very  complex  car- 
bohydrates, called  pentosans  (see  page  50),  occur.  These  pentosans 
through  hydrolysis  by  acids  may  be  transformed  into  pentoses.  Pen- 
toses do  not  ordinarily  occur  in  the  animal  organism,  but  have  been 
found  in  the  urine  of  morphine  habitues  and  others,  their  occurrence 
sometimes  being  a  persistent  condition  without  known  cause.  They 
may  be  obtained  from  the  hydrolysis  of  nucleoproteins  being  present 
in  the  nucleic  acid  complex  of  the  molecule.  Pentoses  are  non- 
fermentable  have  strong  reducing  power  and  form  osazones  with  phenyl- 
hydrazine.  Pentoses  are  an  important  constituent  of  the  dietary  of 
herbivorous  animals.  Glycogen  is  said  to  be  formed  after  the  ingestion 
of  these  sugars  containing  five  oxygen  atoms.  This,  however,  has  not 
been  conclusively  proven.  On  distillation  with  strong  hydrochloric  acid 
pentoses  and  pentosans  yield  furfurol,  which  can  be  detected  by  its 
characteristic  red  reaction  with  aniline-acetate  paper. 

CH2OH 

ARABINOSE,  (CHOH)3 

CHO 


CARBOHYDRATES  37 

Arabinose  is  one  of  the  most  important  of  the  pentoses.  The 
/-arabinose  may  be  obtained  from  gum  arabic,  plum  or  cherry  gum  by 
boiling  for  10  minutes  with  concentrated  hydrochloric  acid.  This 
pentose  is  dextro-rotatory,  forms  an  osazone  and  has  reducing  power, 
but  does  not  ferment.  The  z-arabinose  has  been  isolated  from  the  urine 
and  yields  an  osazone  which  melts  at  i66°-i68°C. 

EXPERIMENTS  ON  ARABINOSE 

1.  Orcinol-Hydrochloric  Acid  Reaction  (Bial).1 — To  5  c.c.  of  Bial's  reagent2  in 
a  test-tube  add  2-3  c.c.  of  the  arabinose  solution  and  heat  the  mixture  gently  until 
the  first  bubbles  rise  to  the  surface.    Immediately  or  upon  cooling  the  solution 
becomes  green  and  a  flocculent  precipitate  of  the  same  color  may  form.     (For 
further  discussion  see  Chapter  XXTV.)    The  test  may  also  be  performed  by 
adding  the  pentose  to  the  hot  reagent. 

It  is  claimed  that  this  test  is  more  delicate  than  the  original  orcinol 
test  (see  3)  and  more  accurate,  since  menthol,  kreosotal,  etc.,  respond 
to  the  original  orcinol  test  but  not  to  BiaPs.  Sachs3  has  offered  sug- 
gestions as  to  modification  of  the  test  in  order  to  avoid  confusion 
with  glycuronic  acid. 

2.  Phloroglucinol-Hydrochloric  Acid  Reaction  (Tollens) . — To  equal  volumes  of 
arabinose  solution  and  hydrochloric  acid  (sp.  gr.  1.09)  add  a  little  phloroglucinol 
and  heat  the  mixture  on  a  boiling  water-bath.    Galactose,  pentose  or  glycuronic 
acid  will  be  indicated  by  the  appearance  of  a  red  color.    To  differentiate  between 
these  bodies  make  a  spectroscopic  examination  and  look  for  the  absorption  band 
between  D  and  E  given  by  pentoses  and  glycuronic  acid.    Differentiate  between 
the  two  latter  bodies  by  the  melting-points  of  their  osazones. 

Compare  the  reaction  with  that  obtained  with  galactose  (page  36). 

3.  Orcinol  Test. — Repeat  2,  using  orcinol  instead  of  phloroglucinol.     A  suc- 
cession of  colors  from  red  through  reddish  blue  to  green  is  produced.     A  green  pre- 
cipitate is  formed  which  is  soluble  in  amyl  alcohol  and  has  absorption  bands  be- 
tween C  and  D. 

4.  Phenylhydrazine  Reaction. — Make  this  test  on  the  arabinose  solution 
according  to  directions  given  under  Glucose,  3,  page  22. 

CH2OH 

I 

XYLOSE,  (CHOH)3 

CHO 

Xylose,  or  wood  sugar;  is  obtained  by  boiling  wood  gums  with  dilute 
acids  as  explained  under  Arabinose,  (see  above) .  It  is  dextro-rotatory, 
forms  an  osazone  and  has  reducing  power,  but  does  not  ferment. 

1Bial:  Deut.  med.  Woch.,  28,  252,  1902,  and  Berl.  klin.  Woch.,  No.  18,  1903. 
2  Orcinol 1.5  gram. 

Fuming  HC1 500  grams. 

Ferric  chloride  (10  per  cent)         20-30  drops. 
'Sachs:  Bioch.  Zeit.,  i,  383,  1906,  and  2,  245,  1906. 


38  PHYSIOLOGICAL  CHEMISTRY 

EXPERIMENTS  ON  XYLOSE 
1-4.     Same  as  for  arabinose  (see  above). 

RHAMNOSE,  C6H1206 

Rhamnose  or  methyl-pentose  is  an  example  of  a  true  carbohydrate 
which  does  not  have  the  H  and  0  atoms  present  in  the  proportion  to 
form  water.  Its  formula  is  CeH^Os.  It  has  been  found  that  rham- 
nose  when  ingested  by  rabbits  or  hens  has  a  positive  influence  upon  the 
formation  of  glycogen  in  those  organisms. 

DISACCHARIDES,  C12H22On 

The  disaccharides  as  a  class  may  be  divided  into  two  rather  dis- 
tinct groups.  The  first  group  would  include  those  disaccharides  which 
are  found  in  nature  as  such,  e.g.,  sucrose  and  lactose,  and  the  second 
group  would  include  those  disaccharides  formed  in  the  hydrolysis  of 
more  complex  carbohydrates,  e.g.,  maltose  and  iso-maltose. 

The  disaccharides  have  the  general  formula  Ci2H22On,  to  which, 
in  the  process  of  hydrolysis,  a  molecule  of  water  is  added  causing  the 
single  disaccharide  molecule  to  split  into  two  monosaccharide  (hexose) 
molecules.  The  products  of  the  hydrolysis  of  the  more  common  di- 
saccharides are  as  follows: 

Maltose  =  glucose  +  glucose. 

Lactose   =  glucose  +  galactose. 

Sucrose  =  glucose  +  fructose. 

All  of  the  more  common  disaccharides  except  sucrose  have  the  power 
of  reducing  certain  metallic  oxides  in  alkaline  solution,  notably  those 
of  copper  and  bismuth.  This  reducing  power  is  due  to  the  presence 
of  the  aldehyde  group  ( — CHO)  in  the  sugar  molecule. 

MALTOSE,  Ci2H22Ou 

Maltose  or  malt  sugar  is  formed  in  the  hydrolysis  of  starch  through 
the  action  of  an  enzyme,  vegetable  amylase  (diastase) ,  contained  in  sprout- 
ing barley  or  malt.  Certain  enzymes  in  the  saliva  and  in  the  pancreatic 
juice  may  also  cause  a  similar  hydrolysis.  Maltose  is  also  an  intermedi- 
ate product  of  the  action  of  dilute  mineral  acids  upon  starch.  It  is 
strongly  dextro-rotatory,  reduces  metallic  oxides  in  alkaline  solution 
and  is  fermentable  by  yeast  after  being  inverted  (see  Polysaccharides, 
page  42)  by  the  enzyme  maltase  of  the  yeast.  In  common  with  the  other 
disaccharides,  maltose  may  be  hydrolyzed  with  the  formation  of  two 
molecules  of  monosaccharide.  In  this  instance  the  products  are  two 
molecules  of  glucose.  With  phenylhydrazine  maltose  forms  an  osa- 
zone;  maltosazone.  The  following  formula  represents  the  probable 
structure  of  maltose: 


CARBOHYDRATES 


39 


CH2OH               CHO 

1                           i 

CHOH 
rrnr 

CHOH 
CHOH 
CHOH 
CHOH 

v_xUxl 

CHOH 
CHOH 

-CH2 

Maltose. 

EXPERIMENTS  ON  MALTOSE 

1-6.  Repeat  Solubility,  Fehling's,  Nylander's,  Phenylhydrazine,  Barfoed's 
and  Fermentation  tests  as  given  under  Glucose,  pages  21-31. 

ISO-MALTOSE,  C12H22On 

Iso-maltose,  an  isomeric  form  of  maltose,  is  formed  along  with  mal- 
tose, by  the  action  of  diastase  upon  starch  paste,  and  also  by  the  action 
of  hydrochloric  acid  upon  glucose.  It  also  occurs  with  maltose  as  one 
of  the  products  of  salivary  digestion.  It  is  dextro-rotatory  and  with 
phenylhydrazine  gives  an  osazone  which  is  characteristic  Iso-maltose 
is  very  soluble  and  reduces  the  oxides  of  bismuth  and  copper  in  alkaline 
solution.  Pure  iso-maltose  is  probably  only  slightly  fermentable. 

LACTOSE,  Ci2H22On 

Lactose  or  milk  sugar  occurs  ordinarily  only  in  milk,  but  has  often 
been  found  in  the  urine  of  women  during  pregnancy  and  lactation.  It 
may  also  occur  in  the  urine  of  normal  persons  after  the  ingestion  of 
unusually  large  amounts  of  lactose  in  the  food.  It  has  a  strong  reducing 
power,  is  dextro-rotatory  and  forms  an  osazone  with  phenylhydrazine. 
Upon  hydrolysis  lactose  yields  one  molecule  of  glucose  and  one  molecule 
of  galactose. 

In  the  souring  of  milk  the  Bacterium  lactis  acidi  or  Streptococcus 
lacticus  and  certain  other  micro-organisms  bring  about  lactic  acid 
fermentation  by  transforming  the  lactose  of  the  milk  into  lactic  acid , 

H    OH 

I      I 
H— C— C— COOH, 

H    H 


4O  ,  PHYSIOLOGICAL   CHEMISTRY 

and  alcohol.  This  same  reaction  may  occur  in  the  alimentary  canal  as 
the  result  of  the  action  of  putrefactive  bacteria.  In  the  preparation  of 
kephyr  and  koumyss  the  lactose  of  the  milk  undergoes  alcoholic  fermen- 
tation, through  the  action  of  ferments  other  than  yeast,  and  at  the 
same  time  lactic  acid  is  produced.  Lactose  and  galactose  yield  mucic 
acid  on  oxidation  with  nitric  acid.  This  fact  is  made  use  of  in  urine 
analysis  to  facilitate  the  differentiation  of  these  sugars  from  other  re- 
ducing sugars.  Mucic  acid  is  COOH(HCOH)4COOH. 

Lactose  is  not  fermentable  by  ordinary  baker's  yeast.  Mathews1 
has  suggested  an  easy  way  to  differentiate  and  determine  lactose  in  the 
presence  of  glucose  based  on  reduction  before  and  after  fermentation 
with  yeast. 

EXPERIMENTS  ON  LACTOSE 

1-6.  Repeat  Solubility,  Fehling's,  Phenylhydrazine,  Barfoed's,  Nylander's 
and  Fermentation  tests  as  given  under  Glucose,  pages  21-31. 

7.  Mucic  Acid  Test.  —  Treat  100  c.c.  of  the  solution  containing  lactose  with 
20  c.c.  of  concentrated  nitric  acid  (sp.  gr.  1.4)  and  evaporate  the  mixture  in  a 
broad,  shallow  glass  vessel  on  a  boiling  water-bath,  until  the  volume  of  the  mix- 
ture has  been  reduced  to  about  20  c.c.  At  this  point  the  fluid  should  be  clear, 
and  a  fine  white  precipitate  of  mucic  acid  should  form. 

If  the  percentage  of  lactose  present  is  low  it  may  be  necessary  to 
cool  the  solution  and  permit  it  to  stand  for  some  time  before  the  pre- 
cipitate will  appear.  It  is  impossible  to  differentiate  between  lactose 
and  galactose  by  this  test,  but  the  reaction  serves  to  differentiate  these 
two  sugars  from  all  other  reducing  sugars. 

Differentiate  lactose  from  galactose  by  means  of  Barfoed's  test, 
page  29. 

SUCROSE,  Ci2H22On 

Sucrose,  also  called  saccharose  or  cane  sugar,  is  one  of  the  most 
important  of  the  sugars  and  occurs  very  extensively  distributed  in 
plants,  particularly  in  the  sugar  cane,  sugar  beet,  sugar  millet  and  in 
certain  palms  and  maples. 

Sucrose  is  dextro-rotatory  and  upon  hydrolysis,  as  before  mentioned, 
the  molecule  of  sucrose  takes  on  a  molecule  of  water  and  breaks  down 
into  two  molecules  of  monosaccharide.  The  monosaccharides  formed 
in  this  instance  are  glucose  and  fructose.  This  is  the  reaction  : 


;  Sucrose  Glucose  Fructose 

This  process  is  called  inversion  and  may  be  produced  by  bacteria,  en- 
zymes, and  certain  weak  acids.  After  this  inversion  the  previously 
strongly  dextro-rotatory  solution  becomes  levb-rotatory.  This  is  due 

1  Mathews:  Jour.  Am.  Med.  Ass'n.,  75,  1568,  1920. 


CARBOHYDRATES  4! 

to  the  fact  that  the  fructose  molecule  is  more  strongly  levo-rotatory 
than  the  glucose  molecule  is  dextro-rotatory.  The  product  of  this 
inversion  is  called  invert  sugar. 

Sucrose  does  not  reduce  metallic  oxides  in  alkaline  solution  and  forms 
no  osazone  with  phenylhydrazine.  Prolonged  boiling  in  the  presence 
of  an  acid  phenylhydrazine  solution  will,  however,  hydrolyze  the  su- 
crose and  cause  the  forrnation  of  glucosozone  and  fructosozone.  It 
is  not  fermentable  directly  by  yeast,  but  must  first  be  inverted  by  the 
enzyme  sucrase  (invertase  or  invertin)  contained  in  the  yeast.  The 
probable  structure  of  sucrose  may  be  represented  by  the  following 
formula.  Note  the  absence  of  any  free  ketone  or  aldehyde  group. 
CH2OH  CH2OH 

I  I 

CHOH  HC 


HC          —  CHOH 

O 


CHOH 

I 
CHOH 


O 


CHOH 

I 
C 


C-        -Q/     CH2OH 
H 

Sucrose. 

EXPERIMENTS  ON  SUCROSE 

i-6.  Repeat  Solubility,  Fehling's,  Nylander's,  Barfoed's,  Phenylhydrazine 
and  Fermentation  tests  according  to  the  directions  given  under  Glucose,  pages 
21-31. 

7.  Inversion  of  Sucrose.— To  25  c.c.  of  sucrose  solution  in  a  beaker  add  5 
drops  of  concentrated  H2SC>4  and  boil  one  minute.  Cool  the  solution  and  render 
neutral  with  saturated  barium  hydroxide.  Filter  off  the  precipitate  of  barium 
sulphate  and  upon  the  resulting  fluid  repeat  the  phenylhydrazine,  Fehling, 
Nylander's  and  Barfoed's  reactions  as  given  under  Glucose,  pp.  22,  25,  27  and  29 ; 
and  the  Resorcinol-Hydrochloric  Acid  Reaction  (Seliwanoff),  as  given  under  Fruc- 
tose, page  35.  Explain  the  results. 

TRISACCHARIDES,  Ci8H32Oi6 

RAFFINOSE 

This  trisaccharide,  also  called  melitose,  or  melitriose  occurs  in  cotton 
seed,  Australian  manna,  and  in  the  molasses  from  the  preparation  of 
beet  sugar.  It  is  dextro-rotatory,  does  not  reduce  Fehling's  solution, 
and  is  only  partly  fermentable  by  yeast. 

RatEnose  may  be  hydrolyzed  by  weak  acids  the  same  as  the  poly- 
saccharides  are  hydrolyzed,  the  products  being  fructose  and  melibiose' 
further  hydrolysis  of  the  melibiose  yields  glucose  and  galactose.  Raffi- 


42  PHYSIOLOGICAL   CHEMISTRY 

nose  may  also  be  hydrolyzed  by  the  enzyme  raffinase,  occurring  in 
certain  bacteria  and  yeasts.1 

POLYSACCHARIDES,  (C6H1005)X 

In  general  the  polysaccharides  are  amorphous  bodies,  a  few,  how- 
ever, are  crystallizable.  Through  the  action  of  certain  enzymes  or 
weak  acids  the  polysaccharides  may  be  hydrolyzed  with  the  formation 
of  monosaccharides.  As  a  class  the  polysaccharides  are  quite  insoluble 
and  are  non-fermentable  until  inverted.  By  inversion  is  meant  the 
hydrolysis  of  disaccharide  or  polysaccharide  sugars  to  form  monosacchar- 
ides, as  indicated  in  the  following  equations: 

(a)  Ci2H22Oii+H2O^2(C6H1206). 

(6)  C6H1005+H20->C6H1206. 

STARCH,  (C6H1006)X 

Starch  is  widely  distributed  throughout  the  vegetable  kingdom, 
occurring  in  grains,  fruits,  and  tubers.  It  occurs  in  granular  form,  the 
microscopical  appearance  being  typical  for  each  individual  starch. 
The  granules,  which  differ  in  size  according  to  the  source,  contain, 
according  to  recent  work,2  at  least  three  principal  ingredients, 
amylocellulose  forming  the  cell  walls,  making  up  about  10  per  cent 
of  the  starch  granules  and  not  reacting  with  iodine;  amylose,  comprising 
about  70  per  cent  of  the  granules  and  giving  a  blue  color  with  iodine; 
and  amylopectin,  the  substance  giving  the  high  viscosity  to  starch 
pastes,  making  up  about  20  per  cent  of  the  granules,  and  giving  no 
color  with  iodine.  Ordinary  starch  is  insoluble  in  cold  water,  but  if 
boiled  with  water  the  cell  -walls  are  ruptured  and  starch  paste  results. 
In  general  starch  gives  a  blue  color  with  iodine. 

Starch  is  acted  upon  by  amylases,  e.g.,  salivary  amylase  (ptyalin) 
and  pancreatic  amylase  (amylopsin),  with  the  formation  of  soluble 
starch,  erythro-dextrin,  achroo-dextrins ,  and  maltose  (see  Salivary  Diges- 
tion, page  53).  Maltose  is  the  principal  end-product  of  this  enzyme 
action.  Upon  boiling  a  starch  solution  with  a  dilute  mineral  acid  a 
series  of  similar  bodies  is  formed,  but  under  these  conditions  glucose 
is  the  principal  end-product. 

Soluble  starch  may  be  prepared  by  the  action  of  dilute  hydro- 
chloric acid  on  ordinary  starch  for  several  weeks  at  room  temperature 
or  at  higher  temperatures  for  a  shorter  period.  By  precipitation  with 
alcohol  this  may  be  obtained  in  a  dry  form  readily  soluble  in  cold  water.3 

1  Kuriyama  and  Mendel:  Jour.  Blol  Chem.,  31,  125,  1917. 

2  Blake:  Jour.  Am.  Chem.  Soc.,  38,  1245,  1916;  39,  315,  1917.     Maquenne  and  Roux: 
Ann.  Chim.  Phys.,  9,  179,  1906. 

3Fernbach:  Proceedings  8th  Int.  Cong.  Appl.  Chem.,  13,  131,  1912. 
Chapin:  Jour.  Ind.  and  Eng.  Chem.,  6,  649,  1914. 


CARBOHYDRATES  43 

EXPERIMENTS  ON  STARCH 

1.  Preparation  of  Potato  Starch. — Pare  a  raw  potato,  comminute  it  upon  a  fine 
grater,  mi*  with  water,  and  "whip  up"  the  pulped  material  vigorously  before 
straining  it  through  cheese  cloth  or  gauze  to  remove  the  coarse  particles.    The 
starch  rapidly  settles  to  the  bottom  and  can  be  washed  by  repeated  decantation. 
Allow  the  compact  mass  of  starch  to  drain  thoroughly  and  spread  it  out  on  a  watch 
glass  to  dry  in  the  air.    If  so  desired  this  preparation  may  be  used  in  the  experi- 
ments which  follow. 

2.  Microscopical  Examination. — Examine  microscopically  the  granules  of  the 
various  starches  submitted  and  compare  them  with  those  shown  in  Figs.  9-19, 
page  44.    The  suspension  of  the  granules  in  a  drop  of  water  will  facilitate  the 
microscopical  examination. 

3.  Solubility. — Try  the  solubility  of  one  form  of  starch  hi  each  of  the  ordinary 
solvents  (see  page  22).    If  uncertain  regarding  the  solubility  in  any  reagent, 
filter  and  test  the  filtrate  with  iodine  solution  as  given  under  5  below.    The  pro- 
duction of  a  blue  color  would  indicate  that  the  starch  had  been  dissolved  by  the 
solvent. 

4.  Iodine  Test. — Place  a  few  granules  of  starch  in  one  of  the  depressions  of  a 
porcelain  test-tablet  and  treat  with  a  drop  of  a  dilute  solution  of  iodine  hi  potas- 
sium iodide.    The  granules  are  colored  blue  due  to  the  formation  of  so-called 
iodide  of  starch.    The  amylo-cellulose  of  the  granule  is  not  stained  as  may  be 
seen  by  examining  microscopically. 

5.  Iodine  Test  on  Starch  Paste.1— Repeat  the  iodine  test  using  the  starch 
paste.    Place  2-3  c.c.  of  starch  paste2  hi  a  test-tube,  add  a  drop  of  the  dilute 
iodine  solution  and  observe  the  production  of  a  blue  color.    Heat  the  tube  and 
note  the  disappearance  of  the  color.    It  reappears  on  cooling. 

In  similar  tests  note  the  influence  of  alcohol  and  of  alkali  upon  the  so-called 
iodide  of  starch. 

The  composition  of  the  iodide  of  starch  is  not  definitely  known.  In  per- 
forming this  test  the  solution  must  always  be  neutral  or  acid  in  reaction. 

6.  Fehling's  Test.— On  starch  paste  (see  page  25). 

7.  Hydrolysis  of  Starch. — Place  about  25  c.c.  of  starch  paste  hi  a  small 
beaker,  add  10  drops  of  concentrated  HC1,  and  boil.    By  means  of  a  small  pipette, 
at  the  end  of  each  minute,  remove  a  cfrop  of  the  solution  to  the  test-tablet  and 
make  the  regular  iodine  test.    As  the  testing  proceeds  the  blue  color  should 
gradually  fade  and  finally  disappear.    At  this  point,  after  cooling  and  neutraliz- 
ing with  solid  KOH,  Fehling's  test  (see  page  25)  should  give  a  positive  result 
due  to  the  formation  of  a  reducing  sugar  from  the  starch.    Make  the  phenyl- 
hydrazine  test  upon  some  of  the  hydrolyzed  starch.    What  sugar  has  been 
formed? 

8.  Influence  of  Tannic  Acid. — Add  an  excess  of  tannic  acid  solution  to  a  small 
amount  of  starch  paste  in  a  test-tube.     The  liquid  will  become  strongly  opaque 
and  ordinarily  a  yellowish-white  precipitate  is  produced.     Compare  this  result  with 
the  result  of  the  similar  experiment  on  dextrin  (page  47). 

1  Preparation  of  Starch  Paste.-^ Grind  2  grams  of  starch  powder  in  a  mortar  with  a  small 
amount  of  cold  water.     Bring  200  c.c.  of  water  to  the  boiling-point  and  add  the  starch  mix- 
ture from  the  mortar  with  continuous  stirring.     Bring  again  to  the  boiling-point  and  allow 
it  to  cool.     This  makes  an  approximate  i  per  cent  starch  paste  which  is  a  very  satisfactory 
strength  for  general  use. 

2  For  this  particular  test  a  starch  paste  of  very  satisfactory  strength  may  be  made  by 
mixing  i  c.c.  of  a  i  per  cent  starch  paste  with  100  c.c.  of  water. 


44 


PHYSIOLOGICAL   CHEMISTRY 


FIG.  9. — POTATO. 


FIG.  12. — RYE. 


m       v^       'jp 

9,p:  ff 

>*>     /"Ci  ^ 

S:  A 


) 


FIG.  15. — BUCKWHEAT. 


FIG.  10. — BEAN.  FIG.  n. — ARROWROOT. 


FIG.  13. — BARLEY. 


FIG.  14. — OAT. 


«fe 


FIG.  16. — MAIZE. 


FIG.  17. — RICE. 


FIG.  18. — PEA.  FIG.  19. — WHEAT. 

STARCH  GRANULES  FROM  VARIOUS  SOURCES.     (Leffmann  and  Beam.} 


CARBOHYDRATES  45 

9.  Diffusibility  of  Starch  Paste.— Test  the  diffusibility  of  starch  paste  through 
animal  membrane,  parchment  paper  or  collodion,  making  a  dialyzer  like  one  of  the 
models  shown  in  Fig.  2,  page  24. 

INULIN,    (C6Hio05)x 

Inulin  is  a  polysaccharide  which  may  be  obtained  as  a  white,  odor- 
less, tasteless  powder  from  the  tubers  of  the  artichoke,  elecampane,  or 
dahlia.  It  has  also  been  prepared  from  the  roots  of  chicory,  dandelion, 
and  burdock.  It  is  very  slightly  soluble  in  cold  water  and  quite  easily 
soluble  in  hot  water.  In  cold  alcohol  of  60  per  cent  or  over  it  is  prac- 
tically insoluble.  Inulin  gives  a  negative  reaction  with  iodine  solution. 
The  "yellow"  color  reaction  with  iodine  mentioned  in  many  books  is 
doubtless  merely  the  normal  color  of  the  iodine  solution.  It  is  very 
difficult  to  prepare  inulin  which  does  not  reduce  Fehling's  solution 
slightly.  This  reducing  power  may  be  due  to  an  impurity.  Prac- 
tically all  commercial  preparations  of  inuMn  possess  considerable 
reducing  power. 

Inulin  is  levo-rotatory  and  upon  hydrolysis  by  acids  or  by  the 
enzyme  inulase  it  yields  the  monosaccharide  fructose  which  readily 
reduces  Fehling's  solution.  The  ordinary  amylolytic  enzymes  occur- 
ring in  the  animal  body  do  not  digest  inulin.  A  small  part  of  the 
ingested  inulin  may  be  hydrolyzed  by  the  acid  gastric  juice,  but  Lewis1 
has  shown  that  "the  value  of  inulin  as  a  significant  source  of  energy 
in  human  dietaries  must  be  questioned." 

EXPERIMENTS  ON  INULIN 

1.  Solubility. — Try  the  solubility  of  inulin  powder  in  hot  and  cold  water  and 
alcohol.    If  uncertain  regarding  the  solubility  in  any  reagent,  filter  and  neutralize 
the  filtrate  if  it  is  alkaline  in  reaction.    Add  a  drop  of  concentrated  hydrochloric 
acid  to  the  filtrate  and  boil  it  for  one  minute.    Render  the  solution  neutral  or 
slightly  alkaline  with  solid  potassium  hydroxide  and  try  Fehling's  test.    What 
is  the  significance  of  a  positive  Fehling's  test  in  this  connection? 

2.  Iodine  Test. — (a)  Place  2-3  c.c.  of  the  inulin  solution  in  a  test-tube  and 
add  a  drop  of  dilute  iodine  solution.    What  do  you  observe? 

(b)  Place  a  small  amount  of  inulin  powder  in  one  of  the  depressions  of  a  test- 
tablet  and  add  a  drop  of  dilute  iodine  solution.  Is  the  effect  any  different  from 
that  observed  above? 

3.  Molisch's  Reaction. — Repeat  this  test  according  to  directions  given  under 
Glucose,  2,  page  22. 

4.  Fehling's  Test. — Make  this  test  on  the  inulin  solution  according  to  the 
instructions  given  under  Glucose,  page  25.    Is  there  any  reduction?2 

5.  Hydrolysis  of  Inulin. — Place  5  c.c.  of  inulin  solution  in  a  test-tube,  add  a 
drop  of  concentrated  hydrochloric  acid  and  boil  it  for  one  minute.    Now  cool 
the  solution,  neutralize  it  with  concentrated  KOH  and  test  the  reducing  action 

1  Lewis:  Journal  American  Medical  Ass'n,  58,  1176,  1912 
1  See  the  discussion  of  the  properties  of  inulin,  above. 


46  PHYSIOLOGICAL   CHEMISTRY 

of  i  c.c.  of  the  solution  upon  i  c.c.  of  diluted  (i  :  4)  Fehling's  solution.  Also 
try  the  Resorcinol-Hydrochloric  Acid  reaction  as  given  on  p.  35.  Explain  the 
result.1 

GLYCOGEN,    (C6Hi005)x 

(For  discussion  and  experiments  see  Muscular  Tissue,  Chapter  XX.) 
LICHENIN,   (C6Hio06)x 

Lichenin  may  be  obtained  from  Cetraria  islandica  (Iceland  moss). 
It  forms  a  difficultly  soluble  jelly  in  cold  water  and  an  opalescent  solu- 
tion in  hot  water.  It  is  optically  inactive  and  gives  no  color  with 
iodine.  Upon  hydrolysis  with  dilute  mineral  acids  lichenin  yields  dex- 
trins  and  glucose.  It  is  said  to  be  most  nearly  related  chemically  to 
starch.  Saliva,  pancreatic  juice,  malt  diastase,  and  gastric  juice  have 
no  noticeable  action  on  lichenin. 

DEXTRIN,  (C6H1005)X 

The  dextrins  are  the  bodies  formed  midway  in  the  stages  of  the 
hydrolysis  of  starch  by  weak  acids  or  an  enzyme.  They  are  amorphous 
bodies  which  are  easily  soluble  in  water,  acids,  and  alkalis,  but  are  in- 
soluble in  alcohol  or  ether.  Dextrins  are  dextro-rotatory  and  are  not 
fermentable  by  yeast. 

The  dextrins  may  be  hydrolyzed  by  dilute  acids  to  form  glucose 
and  by  amylases  to  form  maltose.  With  iodine  one  form  of  dextrin 
(erythro-dextrin)  gives  a  red  color.  Their  power  to  reduce  Fehling's 
solution  is  questioned.  The  lower  members  of  the  dextrin  series  prob- 
ably reduce. 

EXPERIMENTS  ON  DEXTRIN 

1.  Solubility. — Test  the  solubility  of  pulverized  dextrin  in  hot  and  cold  water. 
Dextrin  forms  a  clear  solution  hi  hot  water,  distinguishing  it  from  glycogen  which 
gives  an  opalescent  solution. 

2.  Iodine  Test. — Place  a  drop  of  dextrin  solution  in  one  of  the  depressions 
of  the  test-tablet  and  add  a  dilute  solution  of  iodine  hi  potassium  iodide.    A  red 
color  results  due  to  the  formation  of  the  red  iodide  of  dextrin.    Ordinary  dextrin 
preparations  contain  some  starch  and  hi  the  presence  of  starch  it  is  necessary  to 
have  an  excess  of  iodine  present.    If  the  reaction  is  not  sufficiently  pronounced 
make  a  stronger  solution  from  pulverized  dextrin  and  repeat  the  test.    The 
solution  should  be  slightly  acid  to  secure  the  best  results. 

Make  proper  tests  to  show  that  the  red  iodide  of  dextrin  is  influenced' , by 
heat,  alkali,  and  alcohol  in  a  similar  manner  to  the  blue  iodide  of  starch  (see 
page  43). 

llt  the  inulifl  solution  gave  a  positive  Fehling  test  in  the  last  experiment  it  will  be  neces- 
sary to  check  the  hydrolysis  experiment  as  follows:  To  5  c.c.  of  the  inulin  solution  in  a  test- 
tube  add  one  drop  of  concentrated  hydrochloric  acid,  neutralize  with  concentrated  KOH 
solution  and  test  the  reducing  action  of  i  c.c.  of  the  resulting  solution  upon  i  c.c.  of  diluted 
(i :  4)  Fehling's  solution.  This  will  show  the  normal  reducing  power  of  the  inulin  solution. 
In  case  the  inulin  was  hydrolyzed,  the  Fehling's  test  in  the  hydrolysis  experiment  should 
show  a  more  pronounced  reduction  than  that  observed  in  the  check  experiment. 


CARBOHYDRATES  47 

The  color  in  the  case  of  dextrin  does  not  reappear  as  readily  on  cooling  as 
in  the  case  of  starch. 

3.  To  Detect  Dextrin  in  Presence  of  Starch. — Treat  5  c.c.  of  dextrin  solution 
with  about  10  drops  of  starch  paste.    To  the  mixture  add  an  equal  bulk  of  satu- 
rated ammonium  sulphate,  shake  vigorously,  and  allow  to  stand  for  five  minutes. 
The  starch  is  precipitated.    Filter  through  a  dry  paper,  and  to  a  portion  of  the 
filtrate  add  a  drop  or  two  of  iodine  solution.     The  red  reaction  of  erythro-dextrin 
is  obtained. 

4.  Fehling's  Test. — See  if  the  dextrin  solution  will  reduce  Fehling's  solution. 

5.  Hydrolysis  of  Dextrin. — Take  25  c.c.  of  dextrin  solution  hi  a  small  beaker, 
add  5  drops  of  dilute  hydrochloric  acid,  and  boil.    By  means  of  a  small  pipette, 
at  the  end  of  each  minute,  remove  a  drop  of  the  solution  to  one  of  the  depressions 
of  the  test-tablet  and  make  the  iodine  test.    The  power  of  the  solution  to  produce 
a  color  with  iodine  should  rapidly  disappear.    When  a  negative  reaction  is  ob- 
tained cool  the  solution  and  neutralize  it  with  concentrated  potassium  hydroxide. 
Try  Fehling's  test  (see  page  25).    This  reaction  is  now  strongly  positive,  due  to 
the  formation  of  a  reducing  sugar.    Determine  the  nature  of  the  sugar  by  means 
of  the  phenylhydrazine  test  (see  pages  22  and  23).    s 

6.  Precipitation  by  Alcohol. — To  about  50  c.c.  of  95  per  cent  alcohol  in  a  small 
beaker  add  about  10  c.c.  of  a  concentrated  dextrin  solution.    Dextrin  is  thrown 
out  of  solution  as  a  gummy  white  precipitate. 

7.  Influence  of  Tannic  Acid. — Add  an  excess  of  tannic  acid  solution  to  a 
small  amount  of  dextrin  solution  in  a  test-tube.    No  precipitate  forms.    This 
result  differs  from  the  result  of  the  similar  experiment  upon  starch  (see  Starch,  8, 

page  45)- 

8.  Diffusibility  of  Dextrin.— (See  Starch,  9,  page  45>) 

CELLULOSE,  (C6Hio06)x 

This  complex  polysaccharide  forms  a  large  portion  of  the  cell  wall 
of  plants.  It  is  extremely  insoluble  and  its  molecule  is  much  more  com- 
plex than  the  starch  molecule.  The  best  quality  of  filter  paper  and 
the  ordinary  absorbent  cotton  are  good  types  of  cellulose. 

At  one  time  there  was  but  a  single  known  solvent  for  cellulose. 
Further  investigation  has,  however,  revealed  a  long  list  of  cellulose 
solvents.  (See  Experiment  7.) 

Cellulose  is  not  hydrolyzed  by  boiling  with  dilute  mineral  acids.  It 
may  be  hydrolyzed,  however,  by  treating  with  concentrated  sulphuric 
acid  then  subsequently  diluting  the  solution  with ,  water  and  boiling. 
The  product  of  this  hydrolysis  is  glucose. 

There  is  some  difference  of  opinion  as  to  the  exact  extent  to  which 
cellulose  is  utilized  in  the  animal  organism.  It  is  no  doubt,  more  effi- 
ciently utilized  by  herbivora  than  by  carnivora  or  by  man.  It  is  claimed 
that  about  25  per  cent  may  be  utilized  by  herbivora,  less  than  5  per  cent 
by  dogs  whereas  the  quantity  utilized  by  man  is  "  too  small  for  it  to  play 
a  r61e  of  importance  in  the  diet  of  a  normal  individual."1  In  neither 
man  nor  the  lower  animals  has  there  been  demonstrated  any  formation 

1Swartz:  Transactions  of  the  Connecticut  Academy  of  Arts  and  Sciences,  16,  247, 1911. 


48  PHYSIOLOGICAL   CHEMISTRY 

of  sugar  or  glycogen  from  cellulose.1  It  is  probable  that  the  cellulose 
which  disappears  from  the  intestine  is  transformed  for  the  most  part  into 
fatty  acids.2 

EXPERIMENTS  ON  CELLULOSE 

1 .  Solubility. — Test  the  solubility  of  cellulose  in  water,  dilute  and  concentrated 
acid  and  alkali. 

2.  Iodine  Test. — Add  a  drop  of  dilute  iodine  solution  to  a  few  shreds  of  cotton 
on  a  test-tablet.    Cellulose  differs  from  starch  and  dextrin  in  giving  no  color 
with  iodine. 

3.  Formation  of  Amyloid.3 — Add  10  c.c.  of  dilute  and  5  c.c.  of  concentrated 
H2SO4  to  some  absorbent  cotton  in  a  test-tube.    When  entirely  dissolved  (with- 
out heating)  pour  one-half  of  the  solution  into  another  test-tube,  cool  it  and  dilute 
with  water.    Amyloid  forms  as  a  gummy  precipitate  and  gives  a  brown  or  blue 
coloration  with  iodine. 

After  allowing  the  second  portion  of  the  acid  solution  of  cotton  to  stand  about 
10  minutes,  dilute  it  with  water  hi  a  small  beaker  and  boil  for  15-30  minutes. 
Now  cool,  neutralize  with  solid  KOH  and  test  with  Fehling's  solution.  Glucose 
has  been  formed  from  the  cellulose  by  the  action  of  the  acid. 

4.  Ammoniacal  Cupric  Hydroxide  Solubility  Test   (Schweitzer). — Place  a 
little  absorbent  cotton  hi  a  test-tube,  add  Schweitzer's  reagent,4  and  stir  the 
cellulose  with  a  glass  rod.    When  completely  dissolved  acidify  the  solution  with 
acetic  acid.    An  amorphous  precipitate  of  cellulose  is  produced. 

5.  Hydrochloric  Acid — Zinc  Chloride  Solubility  Test  (Cross  and  Bevan)'.5 — 
Place  a  little  absorbent  cotton  in  a  test-tube,  add  Cross  and  Sevan's  reagent,6 
and  stir  the  cellulose  with  a  glass  rod.    When  solution  is  complete  reprecipitate 
the  cellulose  with  95  per  cent  alcohol. 

6.  Iodine-Zinc  Chloride  Reaction. — Place  a  little  absorbent  cotton  or  quantita- 
tive filter  paper  in  a  test-tube  and  treat  it  with  the  iodine-zinc  chloride  reagent.7 
A  blue  color  forms  on  standing.     Amyloid  has  been  formed  from  the  cellulose 
through  the  action  of  the  ZnCU  and  the  iodine  solution  has  stained  the  amyloid 
blue. 

7.  Other  Cellulose  Solvents. — It  has  been  demonstrated  by  Deming8  that 
there   are   many  excellent  solvents  for  cellulose   (filter  paper).     For  example, 
the  concentrated  aqueous  solutions  of  certain  salts  such  as  antimony  trichloride, 

1Lusk:  American  Journal  of  Physiology,  27,  467,  1911;  also  Hoffmann,  Inaugural  dis- 
sertation, Halle- Wittenberg,  1910. 

2Tappeiner:  Zeitschrift  fur  Biologic,  24,  105   1888. 

3  This  body  derives  its  name  from  amylum  (starch)  and  is  not  to  be  confounded  with 
amyloid,  the  glycoprotein. 

4  Schweitzer's  reagent  is  made  by  adding  potassium  hydroxide  to  a  5  per  cent  solution 
of  copper  sulphate,  which  contains  5  per  cent  of  ammonium  chloride,  until  precipitation  is 
complete.     A  precipitate  of  cupric  hydroxide  forms  and  this  is  filtered  off,  washed,  and 
3  grams  of  the  moist  cupric  hydroxide  brought  into  solution  in  a  liter  of  20  per  cent  am- 
monium hydroxide. 

6  Cross  and  Bevan:  Chemical  News,  63,  p.  66. 

6  Cross  and  Bevan's  reagent  may  be  prepared  by  combining  two  parts  of  concentrated 
hydrochloric  acid  and  one  part  of  zinc  chloride,  by  weight. 

7  The  iodine-zinc  chloride  reagent  as  suggested  by  Nowopokrowsky  (Beihefte  Botan. 
Centr.,  28,  90,  1912)  may  be  made  by  dissolving  20  grams  ZnCl2  in  8.5  c.c.  water  and  when 
cool  introducing  the  iodine  solution  (3  grams  KI+i.5  gram  I  in  60  c.c.  water)  drop  by  drop 
until  iodine  begins  to  precipitate. 

8  Deming:  Journal  American  Chemical  Society,  33,  1515,  1911. 


CARBOHYDRATES  49 

stannous  chloride  and  zinc  bromide.  In  hydrochloric  acid  solution  the  solvent  action 
of  the  above  salts  is  increased.  The  following  salts  are  also  good  solvents  in  hydro- 
chloric acid  solution:  mercuric  chloride,  bismuth  chloride,  antimony  pentachloride, 
tin  tetrachloride  and  titanium  tetrachloride.  In  the  case  of  the  last-mentioned  salt 
the  swollen,  transparent  character  of  the  cellulose  fibers  preliminary  to  solution 
can  be  seen  very  nicely. 

Try  selected  solvents  suggested  by  the  instructor. 


HEMICELLULOSES 

The  hemicelluloses  differ  from  cellulose  in  that  they  may  be  hydro- 
lyzed  upon  boiling  with  dilute  mineral  acids.  They  differ  from  other 
polysaccharides  in  not  being  readily  digested  by  amylases.  Hemi- 
cellulose  may  yield  pentosans,  or  hexosans  upon  hydrolysis. 

Pentosans. — Pentosans  yield  pentoses  upon^  hydrolysis.  So  far  as  is 
known  they  do  not  occur  in  the  animal  kingdom.  They  have,  however, 
a  very  wide  distribution  in  the  vegetable  kingdom,  being  present 
in  leaves,  roots,  seeds,  and  stems  of  all  forms  of  plants,  many  times  in 
intimate  association  or  even  chemical  combination  with  galactans.  In 
herbivora,  pentosans  are  40-80  per  cent  utilized.1  The  few  tests  on 
record  as  to  the  pentosan  utilization  by  man2  indicate  that  80-95 
per  cent  disappear  from  the  intestine.  According  to  Cramer,3  bacteria 
are  efficient  hemicellulose  transformers.  It  has  not  yet  been  dem- 
onstrated that  pentosans  form  glycogen  in  man,  and  for  this  reason 
they  must  be  considered  as  playing  an  unimportant  part  in  human 
nutrition.  Gum  arabic  an  important  pentosan  may  be  hydrolyzed 
by  concentrated  hydrochloric  acid  if  boiled  for  a  short  time.  The 
pentose  arabinose  results  from  such  hydrolysis. 

Galactans. — In  common  with  the  pentosans  the  galactans  have  a  very 
wide  distribution  in  the  vegetable. kingdom.  The  pure  galactans  yield 
galactose  upon  hydrolysis.  One  of  the  most  important  members  of 
the  galactan  group  is  agar-agar,  a  product  prepared  from  certain  types 
of  Asiatic  sea-weed.  This  galactan  is  about  50  per  cent  utilizable  by. 
herbivora4  and  8-27  per  cent  utilizable  by  man.5  Agar  ingestion  has 
been  shown  to  be  a  very  efficient  therapeutic  aid  in  cases  of  chronic 
constipation.6  This  is  particularly  true  when  the- constipation  is  due 
to  the  formation  of  dry,  hard,  fecal  masses  (scybala),  a  type  of  fecal 
formation  which  frequently  follows  the  ingestion  of  a  diet  which  is 

1  Swartz:  Transactions  of  the  Connecticut  Academy  of  Arts  and  Sciences,  16,  247,  1911. 

2  Konig  and  Reinhardt:  Zeil.f.  Untersuchung  der  Nahrungs  u.  Genussmittel,  5,  no,  1902. 
'Cramer:  Inaug.  Diss.,  Hille,  1910. 

4Lohrisch:  Zeit.f.  exper.  Path.  u.  Pharm.,  5,  478,  1908. 
8Saiki:  Jour.  Biol.  Chem.,  2,  251,  1906. 

•Mendel:  Zenlralblat  f.  d.  gesammte  Phys.  u.  Path,  des  Sto/w.,  No.  17,  i,  1908. 
Schmidt:  Miinch.  med.  Woch.,  52,  1970,  1905. 


50  PHYSIOLOGICAL  CHEMISTRY 

very  thoroughly  digested  and  absorbed.  The  agar,  because  of  its 
relative  indigestibility  and  its  property  of  absorbing  water  yields  a 
bulky  fecal  mass  which  is  sufficiently  soft  to  permit  of  easy  evacua- 
tion. Agar  has  been  used  with  good  results  in  the  treatment  of  con- 
stipation in  children.1  Agar  is  not  limited  to  its  use  in  connection 
with  constipation,  but  may  serve  in  other  capacities  as  an  aid  to  intes- 
tinal therapeutics.2 

EXPERIMENTS  ON  A  PENTOSAN 

1.  Solubility. — Test  the  solubility  of  gum  arable  in  hot  and  cold  water  and 
alcohol. 

2.  Iodine  Test. — Add  a  drop  of  dilute  iodine  solution  to  a  little  gum  arable 
on  a  test-tablet.    It  resembles  cellulose  in  giving  no  color  with  iodine. 

3.  Hydrolysis  of  Gum  Arabic. — Introduce  a  little  gum  arabic  into  a  test-tube, 
add  5-10  c.c.  of  strong  hydrochloric  acid  (cone.  HC1  and  water  i :  i)  and  heat  to 
boiling  for  5-10  minutes.    Cool,  neutralize  with  potassium  hydroxide  and  test 
by  the  Fehling  or  some  other  reduction  test.    A  positive  reaction  should  be  ob- 
tained indicating  that  the  gum  arabic  has  been  hydrolyzed  by  the  acid  with  the 
production  of  a  reducing  substance.    What  is  this  reducing  substance?    How 
would  you  identify  it? 

EXPERIMENTS  ON  A  GALACTAN 

1.  Solubility. — Test  the  solubility  of  agar-agar  in  hot  and  cold  water.    Ob- 
serve its  marked  property  of  imbibing  water  (see  above). 

2.  Iodine  Test. — Add  a  drop  of  dilute  iodine  solution  to  a  little  agar-agar  on  a 
test-tablet.    It  resembles  cellulose  in  giving  no  color  with  iodine. 

3.  Hydrolysis  of  Agar-agar. — Introduce  a  few  pieces  of  agar-agar  into  a  test- 
tube,  add  5-10  c.c.  of  strong  hydrochloric  acid  (cone.  HC1  and  water  i  :i)  and 
heat  to  boiling  for  5-10  minutes.    Cool,  neutralize  with  potassium  hydroxide  and 
test  by  the  Fehling  or  some  other  reduction  test.    A  positive  reaction  should  be 
obtained  indicating  that  the  agar-agar  has  been  hydrolyzed  by  the  acid  with  the 
production  of  a  reducing  substance.    What  is  this  reducing  substance?    How 
would  you  identify  it? 

REVIEW  OF  CARBOHYDRATES 

In  order  to  facilitate  the  student's  review  of  the  carbohydrates,  the 
preparation  of  a  chart  similar  to  the  appended  model  is  recommended. 
The  signs  +  and  —  may  be  conveniently  used  to  indicate  positive 
and  negative  reaction.  Only  those  carbohydrates  which  are  of  greatest 
importance  from  the  standpoint  of  physiological  chemistry  have  been 
included  in  the  chart. 

1  Morse:  Journal  American  Medical  Ass'n.,  55,  934,  1910. 
2Einhorn:  Berl.  klin.  Woch.,  49,  113,  1912. 


GARB  OH  YDRATE  S 


MODEL  CHART  FOR  REVIEW  PURPOSES 


off? 

i 

Carbo- 
hydrate 

Solubility 

a-Naphthol  Reaction 
(Molisch) 

1 
.* 

1 

Fehling's  Test 

Nylander-Alme'n  Test 

Barfoed's  Test 

4J 

I 

•1 

,  o 
t-t 

Resorcinol-Hydrochlori 
cid  Reaction  (Seliwano 

Orcinol-Hydrochloric 
Acid  Reaction  (Bial) 

! 
i 

.Si 
"5 

1 

Precipitation  by 
Alcohol 

i 

Rotation 

Diffusibility 

Fermentation 

Products  of  Hydrolysi 

Remarks 

<; 

Glucose. 

Fructose. 

j 

Galactose 

Pentose. 

• 

Maltose. 

Lactose. 

Sucrose. 

\ 

Starch. 

Inulin. 

Glycogen. 

Dextrin. 

Cellulose. 

Gum  Arabic. 

Agar-agar. 

"UNKNOWN"  SOLUTIONS  OF  CARBOHYDRATES 

At  this  point  the  student  will  be  given  several  "unknown"  solutions, 
each  solution  containing  one  or  more  of  the  carbohydrates  studied. 
He  will  be  required  to  detect,  by  means  of  the  tests  on  the  preceding 
pages,  each  carbohydrate  constituent  of  the  several  "  unknown "  solu- 
tions and  hand  in,  to  the  instructor,  a  written  report  of  his  findings,  on 
slips  furnished  by  the  laboratory. 

The  scheme  given  above  may  be  of  use  in  this  connection. 


52 


PHYSIOLOGICAL  CHEMISTRY 


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CHAPTER  III 
SALIVARY  DIGESTION 

THE  saliva  is  secreted  by  three  pairs  of  glands,  the  submaxillary, 
sublingual,  and  parotid,  reinforced  by  numerous  small  glands  called 
buccal  glands.  The  saliva  secreted  by  each  pair  of  glands  possesses 
certain  definite  characteristics  peculiar  to  itself.  For  instance,  in  man 
the  parotid  glands  ordinarily  secrete  a  thin,  watery  fluid,  the  submaxil- 
lary glands  secrete  a  somewhat  thicker  fluid  containing  mucin,  while  the 
product  of  the  sublingual  glands  has  a  more  ^mucilaginous  character. 
The  saliva  as  collected  from  the  mouth  is  the  combined  product  of  all 
the  glands  mentioned.  The  fact  that  there  are  pronounced  variations 
in  the  composition  of  different  fractions  of  saliva  secreted  by  the  same 
normal  individual  on  a  uniform  diet  has  been  emphasized  by  Lothrop 
and  Gies.1 

The  saliva  may  be  induced  to  flow  by  many  forms  of  stimuli,  such  as 
chemical,  mechanical,  electrical,  thermal,  and  psychical,  the  nature  and 
amount  of  the  secretion  depending,  to  a  limited  degree,  upon  the  par- 
ticular class  of  stimuli  employed  as  well  as  upon  the  character  of  the 
individual  stimulus.  For  example,  in  experiments  upon  dogs  it  has  been 
found  that  the  mechanical  stimulus  afforded  by  dropping  several  pebbles 
int«  the  animal's  mouth  caused  the  flow  of  but  one  or  two  drops  of 
saliva,  whereas  the  mechanical  stimulus  afforded  by  sand  thrown  into 
the  mouth  induced  a  copious  flow  of  thin  watery  fluid.  Again,  when 
ice- water  or  snow  was  placed  in  the  animal's  mouth  no  saliva  was  seen, 
while  an  acid  or  anything  possessing  a  bitter  taste,  which  the  dog  wished 
to  reject,  caused  a  free  flow  of  the  thin  saliva.  On  the  other  hand,  when 
articles  of  food  were  placed  in  the  dog's  mouth  the  animal  secreted  a 
thicker  saliva  having  a  higher  mucin  content — a  fluid  which  would  lubri- 
cate the  food  and  assist  in  the  passage  of  the  bolus  through  the  esopha- 
gus. It  was  further  found  that  by  simply  drawing  the  attention  of  the 
animal  to  any  of  the  substances  named  above,  results  were  obtained 
similar  to  those  secured  when  the  substances  were  actually  placed  in  the 
animal's  mouth.  For  example,  when  a  pretense  was  made  of  throw- 
ing sand  into  the  dog's  mouth,  a  watery  saliva  was  secreted,  whereas 
food  under  the  same  conditions  excited  a  thicker  and  more  slimy 
secretion.  The  exhibition  of  dry  food,  in  which  the  dog  had  no  par- 

1  Lothrop  and  Gies:  Journal  of  the  Allied  (Dental)  Societies,  6,  65,  1911. 

S3 


54  PHYSIOLOGICAL    CHEMISTRY 

ticular  interest  (dry  bread),  caused  the  secretion  of  a  large  amount  of 
watery  saliva,  while  the  presentation  of  moist  food,  which  was  eagerly 
desired  by  the  animal,  called  forth  a  much  smaller  secretion,  slimy  in 
character.  These  experiments  show  it  to  be  rather  difficult  to  dif- 
ferentiate between  the  influence  of  physiological  and  psychical  stimuli. 

The  amount  of  saliva  secreted  by  an  adult  in  24  hours  has  been  vari- 
ously placed,  as  the  result  of  experiment  and  observation,  between  1000 
and  1500  c.c.,  the  exact  amount  depending,  among  other  conditions, 
upon  the  character  of  the  food. 

The  saliva  of  adults  ordinarily  has  a  weak,  alkaline  reaction  to  litmus, 
but  becomes  acid,  in  some  instances,  2-3  hours  after  a  meal  or  during 
fasting.  The  saliva  of  the  newborn  is  generally  neutral  to  litmus, 
whereas  that  of  infants,  especially  those  breast-fed,  is  generally  acid.1 
The  alkalinity  of  saliva  is  due  principally  to  di-sodium  hydrogen  phos- 
phate (Na2HP04)  and  its  average  alkalinity  may  be  said  to  be  equiva- 
lent to  0.08-0.1  per  cent  sodium  carbonate.  The  saliva  is  the  most  dilute 
of  all  the  digestive  secretions,  having  an  average  specific  gravity  of  1.005 
and  containing  only  0.5  per  cent  of  solid  matter.  Among  the  solids  are 
found  albumin,  globulin,  mucin,  urea,  the  enzymes  salivary  amylase 
(ptyalin),  maltase,  and  pep  tide-splitting  enzymes,  phosphates,  .and 
other  inorganic  constituents.  Potassium  thiocyanate,  KSCN,  is  also 
generally  present  in  the  saliva.  It  has  been  claimed  that  this  sub- 
stance is  present  in  greatest  amount  in  the  saliva  of  habitual  smokers. 
The  significance  of  thiocyanate  in  the  saliva  is  not  known;  it  probably 
comes  from  the  ingested  thiocyanates  and  from  the  breaking  down  of 
protein  material.  The  attempts  to  show  some  relationship  between 
tooth  decay  and  the  thiocyanate  content  of  the  saliva  secreted  into 
the  mouth  cavity  have  met  with  failure.  The  most  recent  experiments2 
indicate  a  virtual  absence  of  such  relationship. 

The  so-called  tartar  formation  on  the  teeth  is  composed  almost 
entirely  of  calcium  phosphate  with,  some  calcium  carbonate,  mucin, 
epithelial  cells,  and  organic  debris  derived  from  the  food.  The  calcium 
salts  are  held  in  solution  as  acid  salts,  and  are  probably  precipitated  by 
the  ammonia  of  the  breath.  The  various  organic  substances  just  men- 
tioned are  carried  down  in  the  precipitation  of  the  calcium  salts.  ^ 

The  suggestion  has  been  made  that  mucin  is  the  salivary  constituent 
"which  is  particularly  influential  in  the  development  of  local  conditions 
favoring  the  onset  of  dental  decay."3 

The  principal  enzyme  of  the  saliva  is  known  as  salivary  amylase  or 
ptyalin.     This  is  an  amylolytic  enzyme  (see  page  4),  so  called  because  it 
1Allaria:  Monatsschr.  fur  Kinderheilkunde,  10,  179,  1911. 
'Lothrop  and  Gies:  Journal  of  the  Allied  (Dental)  Societies,  6,  65,  1911. 
3 Id.:  Ibid.,  5,  No.  4,  1910. 


SALIVARY   DIGESTION  55 

possesses  the  property  of  transforming  complex  carbohydrates  such  as 
starch  and  dextrin  into  simpler  bodies.  The  action  of  salivary  amylase 
is  one  of  hydrolysis  and  through  this  action  a  series  of  simpler  bodies  are 
formed  from  the  complex  starch.  The  first  product  of  the  action  of  the 
ptyalin  of  the  saliva  upon  starch  paste  is  soluble  starch  (amidulin)  and  its 
formation  is  indicated  by  the  disappearance  of  the-opalescence  of  the 
starch  solution.  This  body  resembles  true  starch  in  giving  a  blue  color 
with  iodine.  Next  follows  the  formation,  in  succession,  of  a  series  of 
dextrins,  called  erythro-dextrin,  a-achroo-dextrin,  fi-achroo-dextrin,  and 
y-achroo-dextrin,  the  erythro-dextrin  being  formed  directly  from  soluble 
starch  and  later  being  itself  transformed  into  a-achroo-dextrin  from  which 
in  turn  are  produced  fi-achroo-dextrin,  y-achroo-dextrin  and  perhaps  other 
dextrins.  Accompanying  each  dextrin  a  small  amount  of  maltose  is 
formed,  the  quantity  of  maltose  growing  gradually  larger  as  the  proc- 
ess of  transformation  progresses.  (Erythro-dextrin  gives  a  red  color 
with  iodine,  the  other  dextrins  give  no  color.)  The  next  stage  is  the 
transformation  of  the  final  dextrin  into  maltose,  the  latter  being  the  prin- 
cipal end-product  of  the  salivary  digestion  of  starch.  At  this  point 
a  small  amount  of  glucose  is  formed  from  the  maltose  through  the  ac- 
tion of  the  enzyme  maltase.  The  above  changes  may  be  represented 

graphically  as  follows:1 

Starch 

I 
Soluble  starch 


I  I 

Erythro-dextrin  Maltose 


'    I  I 

a-Achroo-dextrin  Maltose 

I 


I  I 

j3-Achroo-dextrin  Maltose 


7-Achroo-dextrin  Maltose 


Maltose 

Salivary  amylase  acts  in  alkaline,  neutral,  or  combined  acid  solu- 
tions. It  will  act  in  the  presence  of  relatively  strong  combined  HC1  (see 
page  139),  whereas  a  trace  (0.003  per  cent  to  0.0006  per  cent)  of  ordinary 
free  hydrochloric  acid  will  not  only  prevent  the  action  but  will  destroy 
1  For  a  recent  discussion  of  starch  digestion  see  Blake:  Jour.  Am.  Chem.  Soc.,  38,  I245i 
1916539,  3i 


56  PHYSIOLOGICAL   CHEMISTRY 

the  enzyme.     By  sufficiently  increasing  the  alkalinity  of  the  saliva  to 
litmus,  the  action  of  the  salivary  amylase  is  inhibited. 

It  has  been  shown  by  Cannon  that  salivary  digestion  may  proceed 
for  a  considerable  period  after  the  food  reaches  the  stomach,  owing 
to  the  slowness  with  which  the  contents  are  thoroughly  mixed  with 
the  acid  gastric  juice  and  the  consequent  tardy  destruction  of  the 
enzyme.  Food  in  the  pyloric  end  of  the  stomach  is  soon  mixed  with  the 
gastric  secretion,  but  food  in  the  cardiac  end  is  not  mixed  with  the  acid 
gastric  juice  for  a  considerable  period  of  time  and  in  this  region  during 
that  time  salivary  digestion  may  proceed  undisturbed. 

It  has  been  found  that  salivary  amylase  acts  more  efficiently  when 
the  saliva  is  diluted  from  4  to  7  times.1 

Water  softened  by  lime2  inhibits  the  action  of  salivary  amylase  due 
to  the  presence  of  magnesium  hydroxide  in  this  water.3  Electrolytes 
have  an  important  influence  upon  the  action  of  amylases.  For  ex- 
ample Rockwood4  has  shown  that  Cl,  Br  and  NO3  ions  have  a  pro- 
nounced stimulating  action  upon  salivary  amylase. 

The  question  of  the  adaptation  of  the  salivary  secretion  to  diet  is  one 
which  has  received  considerable  attention.  It  has  been  claimed, 
on  the  basis  of  experimental  evidence,5  that  the  continued  feeding 
of  a  carbohydrate  diet  causes  the  secretion  of  a  saliva  which  con- 
tains a  higher  concentration  of  salivary  amylase  and  one  which  is 
therefore  able  to  more  efficiently  digest  the  carbohydrate  fed.  On  the 
other  hand,  strong  evidence6  has  been  submitted  that  the  amylase  con- 
tent of  the  saliva  is  not  increased  through  the  continued  feeding  of  a 
carbohydrate  diet.  In  general  the  consensus  of  opinion  is  opposed 
to  the  adaptation  of  digestive  secretions  to  diet. 

Maltase,  sometimes  called  glucase,  is  the  second  enzyme  of  the  saliva. 
The  principal  function  of  maltase  is  the  splitting  of  maltose  into  glucose. 
Besides  occurring  in  the  saliva  it  is  also  present  in  the  pancreatic  and 
intestinal  juices.  For  experimental  purposes  the  enzyme  is  ordinarily 
prepared  from  corn.  The  principles  of  the  " reversibility"  of  enzyme 
action  were  first  demonstrated  in  connection  with  maltase  by  Croft  Hill. 

It  is  claimed  that  the  saliva  contains  dipeptide-  and  tripeptide- 
splitting  enzymes.7  Leucyl-glycyl-alanine  was  the  tripeptide  split, 

1  Bergeim  and  Hawk:  Jour.  Am.  Chem.  Soc.,  35,  461,  1913. 

2  Prepared  by  -treating  tap  water  with  one-sixth  its  volume  of  saturated  lime  water, 
allowing  to  stand  24  hours  and  filtering. 

3  Bergeim  and  Hawk:  Jour.  Am.  Chem.  Soc.,  35,  1049,  1913. 

4  Rockwood:  Jour.  Am.  Chem.  Soc.,  41,  228,  1919. 

5  Neilson  and  Terry:  American  Journal  of  Physiology,  15,  406,  1905;  Neilsonand  Lewis: 
Journal  of  Biological  Chemistry,  4,  501,  1908. 

6  Mendel:  American  Journal  of  the  Medical  Sciences,  Oct.,  1909;  Mendel  and  Underbill : 
Journal  of  Biological  Chemistry,  3,  135,  1907;  Mendel,  Chapman  and  Blood:  Medical 
Record,  Aug.  27,  1910. 

7Koelker:  Zeitschrift  fur  physiol.  Chem.,  76,  27,  1911. 


SALIVARY   DIGESTION  57 

whereas  the  cleavage  of  several  dipeptids  was  brought  about.  The 
action  is  similar  to  that  of  intestinal  erepsin  (see  Chapter  XI).  'Later 
investigations  (see  page  202),  apparently  have  demonstrated  that  the 
peptolytic  power  of  saliva,  at  least  in  some  cases,  is  due  to  bacteria. 

Microscopical  examination  of  the  saliva  reveals  salivary  corpuscles,  S 
bacteria,  food  debris,  epithelial  cells,  mucus,  and  fungi.  In  certain  ( 
pathological  conditions  of  the  mouth,  pus  cells  and  blood  corpuscles  / 
may  be  found  in  the  saliva.  ^^ 

EXPERIMENTS  ON  SALIVA 

A  satisfactory  method  of  obtaining  the  saliva  necessary  for  the  ex- 
periments which  follow  is  to  chew  a  small  piece  of  pure  paraffin  wax, 
thus  stimulating  the  flow  of  the  secretion,  which  may  be  collected  in  a 
small  beaker.  Filtered  saliva  is  to  be  used  in  every  experiment  except 
for  the  microscopical  examination. 

i.  Microscopical  Examination. — Examine  a  drop  of  unfiltered  saliva  micro- 
scopically, after  staining  with  methylene  blue,  and  compare  with  Fig.  20  below. 


FIG.  20. — MICROSCOPICAL  CONSTITUENTS  OF  SALIVA. 

o,  Epithelial  cells;  b,  salivary  corpuscles;  c,  fat  drops;  d,  leucocytes;  e,  f  and  g,  bacteria; 

h,  i,  and  k,  fission-fungi. 

2.  Reaction.— Test  the  reaction  to  litmus,  phenolphthalein  and  Congo  red. 

3.  Specific  Gravity. — Partially  fill  a  urinometer  cylinder  with  saliva,  introduce 
the  urinometer,  and  observe  the  reading. 

4.  Test  for  Mucin.— To  a  small  amount  of  saliva  in  a  test-tube  add  1-2  drops 
of  dilute  acetic  acid.    Mucin  is  precipitated. 

5.  Biuret  Test.1— Render  a  little  saliva  alkaline  with  an  equal  volume  of  KOH 
and  add  a  few  drops  of  a  very  dilute  (2-5  drops  in  a  test-tube  of  water)  copper 
sulphate  solution.    The  formation  of  a  purplish-violet  color  is  due  to  mucin. 

This  reaction  is  given  by  protein  material  and  simply  indicates  that  mucin  is 
a  protein. 

6.  Mfflon's  Reaction.2— Add  a  few  drops  of  Millon's  reagent  to  a  little  saliva. 
A  light  yellow  precipitate  formed  by  the  mucin  gradually  turns  red  upon  being 
gently  heated. 

This  reaction  indicates  the  presence  of  protein  (mucin). 

1  The  significance  of  this  reaction  is  pointed  out  on  p.  99. 

2  The  significance  of  this  reaction  is  pointed  out  on  p.  97. 


58  PHYSIOLOGICAL   CHEMISTRY 

7.  Preparation  of  Mucin. — Pour  25  c.c.  of  saliva  into  100  c.c.  of  95  per  cent 
alcohol,  stirring  constantly.    Cover  the  vessel  and  allow  the  precipitate  to  stand 
at  least  12  hours.    Pour  off  the  supernatant  liquid,  collect  the  precipitate  on  a 
filter  and  wash  it,  in  turn,  with  alcohol  and  ether.    Finally  dry  the  precipitate, 
remove  it  from  the  paper  and  make  the  following  tests  on  the  mucin :     (a)  Test 
its  solubility  in  the  ordinary  solvents  (see  page  22);  (b)  Millon's  reaction;  (c) 
dissolve  a  small  amount  in  KOH,  and  try  the  biuret  test  on  the  solution ;  (d)  boil 
the  remainder,  with  10-25  c.c.  of  water  to  which  5  c.c.  of  dilute  HC1  has  been 
added,  until  the  solution  becomes  brownish.    Cool,  render  alkaline  with  solid 
KOH,  and  test  by  Fehling's  solution.    A  reduction  should  take  place. 

Mucin  is  what  is  known  as  a  conjugated  protein  or  glycoprotein 
(see  page  1 1 1)  and  upon  boiling  with  the  acid  the  carbohydrate  group 
in  the  molecule  has  been  split  off  from  the  protein  portion  and  its 
presence  is  indicated  by  the  reduction  of  Fehling's  solution. 

8.  Inorganic  Matter. — Test  for  chlorides,  phosphates,  sulphates,  and  cal- 
cium.   For  chlorides,  acidify  with  HNOs  and  add  AgNOs.    For  phosphates, 
acidify  with  HNO3,  heat  and  add  molybdate  solution.1    For  sulphates,  acidify 
with  HC1  and  add  BaCl2  and  warm.    For  calcium,  acidify  with  acetic  acid,  CH3- 
COOH,  and  add  ammonium  oxalate,  (NH4)2C2O4. 

9.  Viscosity  Test. — Place  filter  papers  in  two  funnels,  and  to  each  add  an  equal 
quantity  of  starch  paste  (5  c.c.).    Add  a  few  drops  of  saliva  to  one  lot  of  paste  and 
an  equivalent  amount  of  water  to  the  other.    Note  the  progress  of  filtration  in 
each  case.    Why  does  one  solution  filter  more  rapidly  than  the  other? 

10.  Test  for  Nitrites. — Add  1-2  drops  of  dilute  H2S04  to  a  little  saliva  and 
thoroughly  stir.    Now  add  a  few  drops  of  a  potassium  iodide  solution  and  some 
starch  paste.    Nitrous  acid  is  formed  which  liberates  iodine,  causing  the  formation 
of  the  blue  iodide  of  starch. 

11.  Thiocyanate  Tests. — (a)  Ferric  Chloride  Test— To  a  little  saliva  in  a 
small  porcelain  crucible,  or  dish,  add  a  few  drops  of  dilute  ferric  chloride  and 
acidify  slightly  with  HC1.    Red  ferric  thiocyanate  Fe(SCN)8  forms.    To  show 
that  the  red  coloration  is  not  due  to  iron  phosphate  add  a  drop  of  HgCl2  when 
colorless  mercuric  thiocyanate  forms. 

(b)  Solera's  Reaction. — This  test  depends  upon  the  liberation  of  iodine  through 
the  action  of  thiocyanate  upon  iodic  acid.  Moisten  a  strip  of  starch  paste-iodic  acid 
test  paper2  with  a  little  saliva.  If  thiocyanate  be  present  the  test  paper  will  assume 
a  blue  color,  due  to  the  liberation  of  iodine  and  the  subsequent  formation  of  the  so- 
called  iodide  of  starch. 

12.  Digestion  of  Starch  Paste. — To  25  c.c.  of  starch  paste  hi  a  small  beaker, 
add  5  drops  of  saliva  and  stir  thoroughly.    At  intervals  of  a  minute  remove  a 
drop  of  the  solution  to  one  of  the  depressions  in  a  test-tablet  and  test  by  the  io- 
dine test.    If  th.e  blue  color  with  iodine  still  forms  after  five  minutes,  add  another 
5  drops  of  saliva.    The  opalescence  of  the  starch  solution  should  soon  disappear, 
indicating  the  formation  of  soluble  starch  which  gives  a  blue  color  with  iodine. 

1  See  "Reagents  and  Solutions,"  p.  638. 

2  This  test  paper  is  prepared  as  follows:  Saturate  a  good  quality  of  filter  paper  with  0.5 
per  cent  starch  paste  to  which  has  been  added  sufficient  iodic  acid  to  make  a  i  per  cent 
solution  of  iodic  acid  and  allow  the  paper  to  dry  in  the  air.     Cut  it  in  strips  of  suitable  size 
and  preserve  for  use. 


SALIVARY  DIGESTION  59 

This  body  should  soon  be  transformed  into  ery  thro -dextrin  which  gives  a  red 
color  with  iodine,  and  this  in  turn  should  pass  into  achroo -dextrin  which  gives  no 
color  with  iodine.  This  is  called  the  achromic  point.  When  this  point  is  reached 
test  by  Fehling's  test  to  show  the  production  of  a  reducing  body.  A  positive 
Fehling's  test  may  be  obtained  while  the  solution  still  reacts  red  with  iodine 
inasmuch  as  some  maltose  is  formed  from  the  soluble  starch  coincidentiy  with 
the  formation  of  the  erythro -dextrin.  How  long  did  it  take  for  a  complete  trans- 
formation of  the  starch?  For  a  graphic  representation  of  the  above  changes  see 
page  55. 

13.  Separation  of  the  Products  of  Salivary  Digestion.— To  25  c.c.  of  starch 
paste  in  a  small  beaker  add  i  c.c.  of  saliva  and  stir  thoroughly.    At  intervals  of 
one  minute  test  a  drop  of  the  mixture  by  the  iodine  test.    If  the  blue  color  per- 
sists after  five  minutes  add  another  i  c.c.  of  saliva.    When  the  mixture  reacts 
red  with  iodine,  indicating  that  erythro-dextrin  has  been  formed,  add  100  c.c.  of- 
95  per  cent  alcohol.    Allow  to  stand  until  the  white  precipitate  has  settled. 
Filter,  evaporate  the  filtrate  to  dryness,  dissolve  the^residue  in  5-10  c.c.  of  water 
and  try  Fehling's  test  (page  25)  and  the  phenylhydrazine  reaction  (see  Glucose,  3, 
page  22).    On  the  dextrin  precipitate  try  the  iodine  test  (page  43).    Also  hydro- 
lyze  the  dextrin  as  given  under  Dextrin,  5,  page  47. 

14.  Digestion  of  Raw  Starch. — In  a  test-tube  shake  up  a  small  amount  of  raw 
starch  with  a  little  water.    Add  a  few  drops  of  saliva,  mix  well,  and  allow  to 
stand.    After  10-20  minutes  filter  and  test  the  filtrate  by  Fehling's  test.    What 
is  the  result? 

It  has  been  shown  that  raw  corn  starch  and  wheat  starch  are  com- 
pletely digested  and  absorbed  by  normal  adults  whereas  raw  potato 
starch  is  somewhat  less  than  80  per  cent,  available.'1 

15.  Digestion  of  Inulin. — To  5  c.c.  of  inulin  solution  in  a  test-tube  add  10  drops 
of  saliva  and  place  the  tube  in  the  incubator  or  water-bath  at  4o°C.    After  one- 
half  hour  test  the  solution  by  Fehling's  test.2    Is  any  reducing  substance  present? 
What  do  you  conclude  regarding  the  salivary  digestion  of  inulin? 

1 6.  Influence  of  Temperature.— In  each  of  four  tubes  place  about  5  c.c.  of 
starch  paste.    Immerse  one  tube  in  cold  water  from  the  faucet,  keep  a  second  at 
room  temperature,  and  place  a  third  in  the  incubator  or  the  water-bath  at  4O°C. 
(If  the  temperature  of  the  bath  or  incubator  is  allowed  to  rise  to  7o°C.  or  over  the 
enzyme  is  destroyed  and  no  digestion  takes  place.)    Now  add  to  the  contents  of 
each  of  these  three  tubes  two  drops  of  saliva  and  shake  well;  to  the  contents  of 
the  fourth  tube  add  two  drops  of  boiled  saliva.    Test  frequently  by  the  iodine 
test,  using  the  test-tablet,  and  note  in  which  tube  the  most  rapid  digestion  occurs. 
Explain  the  results. 

17.  Influence  of  Dilution.3 — Take  a  series  of  six  test-tubes  each  containing 
9  c.c.  of  water.    Add  i  c.c.  of  saliva  to  tube  i  and  shake  thoroughly.    Transfer 
i  c.c.  of  the  solution  from  tube  i  to  tube  2  and  after  mixing  thoroughly  6  saliva 

'  ^angworthy  and  Deuel:  Jour.  Biol.  Chem.,  42,  27,  1920. 

*  If  the  inulin  solution  gives  a  reduction  before  being  acted  upon  by  the  saliva  it  will  be 
necessary  to  determine  the  extent  of  the  original  reduction  by  means  of  a  "check"  test  (see 
p.  46). 

3  The  technic  of  Wohlgemuth's  method  (see  Chapter  X)  may  be  employed  in  this  test 
if  so  desired. 


60  PHYSIOLOGICAL   CHEMISTRY 

i  c.c.  from  tube  2  to  tube  3.  Continue  in  this  manner  until  you  have  transfer 
solutions  of  gradually  decreasing  strength.  Now  add  starch  paste  in  equal 
amounts  to  each  tube,  mix  very  thoroughly,  and  place  in  the  incubator  or  water- 
bath  at  40°C.  After  10-20  minutes  test  by  both  the  iodine  and  Fehling's  tests. 
In  how  great  dilution  does  your  saliva  act? 

18.  Influence  of  Acids  and  Alkalis. — (a)  Influence  of  Free  Acid. — Prepare  a 
series  of  six  tubes  in  each  of  which  is  placed  4  c.c.  of  one  of  the  following  strengths 
of  free  HC1:  0.2  per  cent,  o.i  per  cent,  0.05  per  cent,  0.025  per  cent,  0.0125  per 
cent  and  0.006  per  cent.  Now  add  2  c.c.  of  starch  paste  to  each  tube  and  shake 
them  thoroughly.  Complete  the  solutions  by  adding  2  c.c.  of  saliva  to  each  and 
repeat  the  shaking.  The  total  acidity  of  this  series  would  be  as  follows :  o.i  per 
cent,  0.05  per  cent,  0.025  per  cent,  0.0125  per  cent,  0.006  per  cent  and  0.003  per 
cent.  Place  these  tubes  on  the  water-bath  at  4o°C.  for  10-20  minutes.  Divide 
the  contents  of  each  tube  into  two  parts,  testing  one  part  by  the  iodine  test  and 
testing  the  other,  after  neutralization,  by  Fehling's  test.  What  do  you  find? 

(b)  Influence  of  Combined  Acid  (Protein  Salt). — Repeat  the  first  three  ex- 
periments of  the  above  series  using  combined  hydrochloric  acid  (see  page  139) 
instead  of  the  free  acid.    How  does  the  action  of  the  combined  acid  differ  from 
that  of  the  free  acid?     (For  a  discussion  of  combined  acid  see  page  139.) 

(c)  Influence  of  Alkali. — Repeat  the  first  four  experiments  under  (a)  replac- 
ing the  HC1  by  2  per  cent,  i  per  cent,  0.5  per  cent  and  0.25  per  cent  NajCO3. 
Neutralize  the  alkalinity  before  trying  the  iodine  test  (see  Starch,  5,  page  43). 

(d)  Nature  of  the  Action  of  Acid  and  Alkali. — Place  2  c.c.  of  saliva  and  2  c.c. 
of  0.2  per  cent  HC1  in  a  test-tube  and  leave  for  15  minutes.    Neutralize  the 
solution,  add  4  c.c.  of  starch  paste  and  place  the  tube  in  the  incubator  or  water- 
bath  at  40°C.    In  ro  minutes  test  by  the  iodine  and  Fehling's  tests  and  explain 
the  result.    Repeat  the  experiment,  replacing  the  0.2  per  cent  HC1  by  2  per  cent 
Na2CO3.    What  do  you  deduce  from  these  two  experiments? 

19.  Influence  of  Metallic  Salts,  etc. — In  each  of  a  series  of  tubes  place  4  c.c. 
of  starch  paste  and  0.5  c.c.  of  one  of  the  solutions  named  below.     Shake  well,  add 
0.5  c.c.  of  saliva  to  each  tube,  thoroughly  mix,  and  place  in  the  incubator  or  water- 
bath  at  4o°C.  for  10-20  minutes.    Show  the  progress  of  digestion  by  means  of  the 
iodine  and  Fehling  tests.     Use  the  following  chemicals:  Metallic  salts,  10  per  cent 
lead  acetate,  2  per  cent  copper  sulphate,  5  per  cent  ferric  chloride,  8  per  cent  mer- 
curic chloride;  Neutral  salts,  10  per  cent  sodium  chloride,  10  per  cent  magnesium 
sulphate,  3  per  cent  barium  chloride,  10  per  cent  Rochelle  salt.     Also  try  the  influ- 
ence of  2  per  cent  carbolic  acid,  95  per  cent  alcohol,  and  ether  and  chloroform. 
What  are  your  conclusions? 

Antiseptics  do  not  necessarily  inhibit  enzyme  action. 

20.  Excretion  of  Potassium  Iodide. — Ingest  a  small  dose  of  potassium  iodide 
(0.2  gram)  contained  in  a  gelatin  capsule,  quickly  rinse  out  the  mouth  with 
water,  and  then  test  the  saliva  at  once  for  iodine.    This  test  should  be  negative. 
Make  additional  tests  for  iodine  at  two-minute  intervals.    The  test  for  iodine  is 
made  as  follows:  Take  i  c.c.  of  NaNO2  and  i  c.c.  of  dilute  H2SO41  in  a  test- 
tube,  add  a  little  saliva  directly  from  the  mouth,  and  a  small  amount  of  starch 
paste.    The  formation  of  a  blue  color  signifies  that  the  potassium  iodide  is  being 
excreted  through  the  salivary  glands.    Note  the  length  of  time  elapsing  between 

1  Instead  of  this  mixture  a  few  drops  of  HN08  possessing  a  yellowish  or  brownish  color 
due  to  the  presence  of  HNO2  may  be  employed.  J  „ 


SALIVARY  DIGESTION  6 1 

the  ingestion  of  the  potassium  iodide  and  the  appearance  of  the  first  traces  of  the 
substance  in  the  saliva.  If  convenient,  the  urine  may  also  be  tested.  The 
chemical  reactions  taking  place  in  this  experiment  are  indicated  hi  the  following 
equations : 

(a)  2NaN02+H2S04^2HN02+Na2S04. 

(*)  2KI+H2S04-»2HI+K2S04. 

(c)  2HN02+     2HI->I2+2H20+2NO. 


CHAPTER  IV 
PROTEINS:1  THEIR  DECOMPOSITION  AND  SYNTHESIS 

THE  proteins  are  a  class  of  substances  which,  in  the  light  of  our  pres- 
ent knowledge,  consist,  in  the  main,  of  combinations  of  a-amino  acids  or 
their  derivatives.  These  protein  substances  form  the  chief  constituents 
of  many  of  the  fluids  of  the  body,  constitute  the  organic  basis  of  animal 
tissue,  and  at  the  same  time  occupy  a  decidedly  preeminent  position 
among  our  organic  food-stuffs.  They  are  absolutely  necessary  to  the 
uses  of  the  animal  organism  for  the  continuance  of  life  and  they  cannot 
be  satisfactorily  replaced  in  the  diet  of  such  an  organism  by  any  other 
dietary  constituent  either  organic  or  inorganic.  Such  an  organism  may 
exist  without  protein  food  for  a  period  of  time,  the  length  of  the  period 
varying  according  to  the  specific  organism  and  the  nature  of  the  substi- 
tution offered  for  the  protein  portion  of  the  diet.  Such  a  period  is,  how- 
ever, distinctly  one  of  existence  rather  than  one  of  normal  life  and  one 
which  is  consequently  not  accompanied  by  such  a  full  and  free  exercise 
of  the  various  functions  of  the  organism  ,as  would  be  possible  upon  an 
evenly  balanced  ration,  i.e.,  one  containing  the  requisite  amount  of 
protein  food.  These  protein  substances  are,  furthermore,  essential 
constituents  of  all  living  cells  and  therefore  without  them  vegetable  life 
as  well  as  animal  life  is  impossible. 

The  proteins,  which  constitute  such  an  important  group  of 
substances,  differ  from  carbohydrates  and  fats  very  decidedly  in 
elementary  composition.  In  addition  to  containing  carbon,  hydrogen, 
and  oxygen,  which  are  present  in  fats  and  carbohydrates,  the  pro- 
teins invariably  contain  nitrogen  in  their  molecule  and  generally 
sulphur  also.  Proteins  have  also  been  described  which  contain  phos- 
phorus, iron,  copper,  iodine,  manganese,  and  zinc.  The  percentage 
composition  of  the  more  important  members  of  the  group  of  protein 
substances  would  fall  within  the  following  limits:  C  =  50-55  per 
cent,  H  =  6~7.3  per  cent,  0=19-24  per  cent,  N=  15-19  per  cent, 
8  =  0.3-2.5  per  cent,  P  =  0.4- 0.8  per  cent  when  present.  When  iron, 
copper,  iodine,  manganese,  or  zinc  are  present  in  the  protein  molecule 

1  The  term  proteid  has  been  very  widely  used  by  English-speaking  scientists  to  signify  the 
class  of  substances  we  have  called  proteins. 

62 


PROTEINS  63 

they  are  practically  without  exception  present  only  in  traces  and 
with  the  exception  of  iodine  are  probably  not  constituents  of  the 
protein  molecule.1 

Of  all  the  various  elements  of  the  protein  molecule,  nitrogen  is  by  far 
the  most  important.  The  human  body  needs  nitrogen  for  the  continua- 
tion of  life,  but  it  cannot  use  the  nitrogen  of  the  air  or  that  in  various 
other  combinations  as  we  find  it  in  nitrates,  nitrites,  etc.  However,  in 
the  protein  molecule  the  nitrogen  is  present  in  a  form  which  is  utilizable 
by  the  body.  The  protein  molecule  is  made  up  of  various  nitrogen- 
containing  components,  which  may  be  classified  in  the  manner  indi- 
cated: I,  monamino  acids;  II,  diamino  acids;  III,  substances  containing 
nitrogen  in  imid  form,  and  IV,  substances  containing  nitrogen  as  in 
guanidin. 

The  actual  structure  of  the  protein  molecule  is  still  unknown,  and  we 
have  as  yet  no  means  by  which  its  molecular  weight  can  be  even  approxi- 
mately established.  The  many  attempts  which  have  been  made  to 
determine  this  have  led  to  very  different  results,  some  of  which  are  given 
in  the  following  table: 

Globin  =15000—16086 

Oxyhemoglobin    =  14800—15000  —  16655  —  16730 

Of  these  figures,  those  given  for  oxyhemoglobin  deserve  the  most 
consideration,  for  these  are  based  on  the  atomic  ratios  of  the  sulphur 
and  iron  contained  in  this  substance.  The  simplest  formula  that  can 
be  calculated  from  analyses  of  oxyhemoglobin,  namely, 


serves  to  show  the  great  complexity  of  this  substance. 

The  decomposition2  of  protein  substances  may  be  brought  about  by 
oxidation  or  hydrolysis,  but  inasmuch  as  the  hydrolytic  procedure  has 
been  productive  of  the  more  satisfactory  results,  that  type  of  decomposi- 
tion procedure  alone  is  used  at  present.  This  hydrolysis  of  the  protein 
molecule  may  be  accomplished  by  acids,  alkalis,  or  superheated  steam, 
and  in  digestion  by  the  action  of  the  proteolytic  enzymes.  The  char- 
acter of  the  decomposition  products  varies  according  to  the  method 
utilized  in  tearing  the  molecule  apart.  Bearing  this  in  mind,  we  may 
say  that  the  decomposition  products  of  proteins  include  proteoses,  pep- 
tones, peptides,  carbon  dioxide,  ammonia,  hydrogen  sulphide,  and  amino 

1  Some  investigators  regard  these  elements  as  contaminations,  or  constituents  of  some 
non-protein  substance  combined  with  the  protein. 

2  The  terms  "degradation,"  "dissociation,"  and  "cleavage,"  are  often  used  in  this  con- 
nection. 


64  PHYSIOLOGICAL  CHEMISTRY 

acids.  These  amino  acids1  constitute  a  long  list  of  important  substances 
which  contain  nuclei  belonging  either  to  the  aliphatic,  carbocyclic,  or 
heterocydic  classes  of  compounds.  The  list  includes  glycocoll  (glycine), 
alanine,  serine,  phenylalanine,  tyrosine,  cystine,  tryptophane,  histidine, 
valine,  arginine,  leucine,  isoleucine,  lysine,  aspartic  acid,  glutamic  acid, 
proline,  oxyproline,  and  norleucine.  Of  these  amino  acids,  tyrosine 
and  phenylalanine  contain  carbocyclic  nuclei;  histidine,  proline,  and 
tryptophane  contain  heterocyclic  nuclei;  and  the  remaining  members 
of  the  list,  as  given,  contain  aliphatic  nuclei.  The  amino  acids  are 
preeminently  the  most  important  class  of  protein  decomposition  prod- 
ucts. These  amino  acids  are  all  a-amino  acids,  and,  with  the  exception 
of  glycocoll,  are  all  optically  active.  Furthermore,  they  are  amphoteric 
substances  and  consequently  are  able  to  form  salts  with  both  bases  and 
acids.  These  properties  are  inherent  in  the  NH2  and  COOH  groups  of 
the  amino  acids. 

The  decomposition  products  of  protein  may  be  grouped  as  pri- 
mary and  secondary  decomposition  products.  By  primary  products  are 
meant  those  which  exist  as  radicals  within  the  protein  molecule  and 
which  are  liberated,  upon  cleavage  of  this  molecule,  with  their  carbon 
chains  intact  and  the  position  of  their  nitrogen  unaltered.  The  second- 
ary products  are  those  which  result  from  the  disintegration  of  the 
primary  cleavage  products.  No  matter  what  method  is  used  to  de- 
compose a  given  protein  molecule,  the  primary  products  are  largely  the 
same  under  all  conditions.2 

In  the  process  of  hydrolysis  the  protein  molecule  is  gradually  broken 
down  and  less  complicated  aggregates  than  the  original  molecule  are 
formed,  which  are  known  as  proteoses,  peptones,  and  peptides,  and  which 
still  possess  true  protein  characteristics.  Further  hydrolysis  causes  the 
ultimate  transformation  of  these  substances,  of  a  protein  nature,  into  the 
amino  acids  of  known  chemical  structure.  In  this  decomposition  the 
protein  molecule  is  not  broken  down  in  a  regular  manner  into  J^,  J4, 
%  portions  and  the  amino  acids  formed  in  a  group  at  the  termination  of 
the  hydrolysis.  On  the  contrary,  certain  amino  acids  are  formed  very 
early  in  the  process,  in  fact  while  the  main  hydrolytic  action  has  pro- 
ceeded no  further  than  the  proteose  stage.  Gradually  the  complexity 
of  the  protein  portion  undergoing  decomposition  is  simplified  by  the 
splitting  off  of  the  amino  acids  and  finally  it  is  so  far  decomposed 
through  previous  cleavages  that  it  yields  only  amino  acids  at  the 
succeeding  cleavage.  In  shortj  the  general  plan  of  the  hydrolysis  of 
the  protein  molecule  is  similar  to  the  hydrolysis  of  starch.  In  the  case 

1For  a  discussion  of  amino  acids  see  Underbill's  "Physiology  of  Amino  Acids,"  Yale 
University  Press,  Nov.,  1915. 

2  Alkaline  hydrolysis  yields  urea  and  ornithine  which  result  from  arginine.  {he  product  of 
acid  hydrolysis. 


PROTEINS  65 

of  starch  there  is  formed  a  series  of  dextrins  of  gradually  decreasing 
complexity  and  coincidently  with  the  formation  of  each  dextrin  a  small 
amount  of  sugar  is  split  off  and  finally  nothing  but  sugar  remains.  In 
the  case  of  protein  hydrolysis  there  is  a  series  of  proteins  of  gradually 
decreasing  complexity  produced  and  coincidently  with  the  formation  of 
each  new  protein  substance  amino  acids  are  split  off  and  finally  the  sole 
products  remaining  are  amino  acids. 

Inasmuch  as  diversity  in  the  method  of  decomposing  a  given  protein 
does  not  result  in  an  equally  diversified  line  of  decomposition  products, 
but,  on  the  other  hand,  yields  products  which  are  quite  comparable  in 
character,  it  may  be  argued  that  there  are  probably  well-defined  lines  of 
cleavage  in  the  individual  protein  molecule  and  that  no  matter  what  the 
force  brought  to  bear  to  tear  such  a  molecule  apart,  the  disintegration, 
when  it  comes,  will  yield  in  every  case  certain  definite  fragments. 
These  fragments  may  be  called  the  "building  stones"  of  the  protein 
molecule,  a  term  used  by  some  of  the  German  investigators.  Take,  for 
example,  the  decomposition  of  protein  which  may  be  brought  about 
through  the  action  of  the  enzyme  trypsin  of  the  pancreatic  juice. 
When  this  enzyme  is  allowed  to  act  upon  a  given  protein,  the  latter  is 
disintegrated  in  a  series  of  definite  cleavages,  resulting  in  the  formation 
of  proteases,  peptones,  and  peptides  in  regular  order,  the  peptides  being 
the  last  of  the  decomposition  products  which  possess  protein  character- 
istics. They  are  all  built  up  from  amino  acids  and  are  therefore  closely 
related  to  these  acids  on  the  one  side  and  to  peptones  on  the  other. 
We  have  di-,  tri-,  tetra-,  penta-,  deca-,  and  poly-peptides  which  are 
named  according  to  the  number  of  amino  acids  included  in  the  peptide 
molecule.  Following  the  peptides  there  are  a  diverse  assortment  of 
monamino  and  diamino  acids  which  constitute  the1  final  products  of 
the  protein  decomposition.  These  acids  are  devoid  of  any  protein 
characteristics  and  are  therefore  decidedly  different  from  the  original 
substance  from  which  they  were  derived.  From  a  protein  of  huge 
molecular  weight,  a  typical  colloid,  perhaps  but  slightly  soluble,  and 
entirely  non-diffusible,  we  have  passed  by  way  of  proteoses,  peptones, 
and  peptides  to  a  class  of  simpler  crystalline  substances  which  are,  for 
the  most  part,  readily  soluble  and  diffusible. 

These  amino  acids  after  their  production  in  the  process  of  digestion, 
as  just  indicated,  are  synthesized  within  the  cells  of  the  crganism  to 
form  protein  material  which  goes  to  build  up  the  tissues  of  the  body. 
It  is  thus  seen  that  the  amino  acids  are  of  prime  importance  in  the 
animal  economy.  It  was  formerly  believed  that  these  essential  factors 
in  metabolism  and  nutrition  could  not  be  produced  within  the  animal 
organism  from  their  elements,  but  were  only  yielded  upon  the  hydrol- 
5 


66 


PHYSIOLOGICAL  CHEMISTRY 


ysis  of  ingested  protein  of  animal  or  vegetable  origin.  Experi- 
ments, however,  by  Abderhalden  and  by  Grafe  and  Schlapfer  and  others 
indicate  that  the  nitrogen  of  food  protein  may  in  part  be  replaced  by 
ammonium  salts.  Experiments  by  Osborne  and  others  also  indicate 
amino  acid  synthesis  by  animals. 

Important  data  regarding  the  decomposition  products  of  the  protein 
molecule  are  given  in  the  tables  which  follow. 

COMPARISON  OF  THE  DECOMPOSITION  PRODUCTS  OF  PROTAMINES,  AND 

OTHER  PROTEINS. 


Decomposition 
Product. 

PROTAMINES.* 
(Per  cent  of  total  nitrogen  of 
amino  acid.) 

OTHER  PROTEINS. 
(Per  cent  of  amiro  acids  in 
proteins.) 

Scombrine. 

Cyclopterine. 

Sturine. 

a-cyprinine. 

0-cyprinine. 

Clupeine. 

Salmine. 

Gliadin* 
(wheat). 

Edestin.* 

Casein.1 

Gelatin.5  . 

Globin.* 

jj 

? 

Glycocoll  

o 

3-8 

o 

16.5 

0 

0 

Alanine.  

+ 

+ 

+ 

2.0O 

3-6 

1-5 

0.8 

4-2 

9-79 

Valine  

+ 

+ 

+ 

1.65 

3-34 

6.2 

7-2 

1  .0 



1.88 

Leucine  

+ 

6.62 

14-5 

9-4 

7-1 

29.0 

19-55 

Proline  

3.8 

+ 

4-3 

13-22 

4.1 

6.7 

9-5 

2.3 

9.04 

Phenylalanine        .  .    . 

2.35 

3-1 

3-2 

1.4 

4.2 

6.55 

Aspartic  acid  

0.58 

4-5 

1.4 

3-4 

4-4 

1.71 

Glutamic  acid  

43-66 

18.74 

II.  0 

5.8 

1-7 

26.17 

Serine  

+ 

3-25 

0.13 

0-33 

o.S 

0.4 

0.6 

1.02 

+ 

1.5 

1.  50* 

2.1 

4-5 

O.OI 

1-3 

3-55 

Arginine  

88.8 

67.7 

63-5 

8.7 

28.0 

88.0 

89.2 

2.70* 

14-2 

4.84 

8.2 

5-4 

i.SS 

Lysine  . 

8.4 

30.3 

6.6 



0.6 

1-7 

5-95 

5-9 

4-3 

0 

II   8 

i.50« 

2.2 

2.50 

0.9 

II.  0 

0.82 

+ 

+ 

I.  01° 

+ 

1-5 

0 

+ 

0 

Cystine 

0.45 

1.  00 

0.065 

0 

0-3 

? 

? 

0" 

0.23 

14.1 

I.O 

? 

Ammonia 

5-22 

2.3 

1.61 

0.4 

3.64 

When  we  examine  the  formulas  of  the  principal  members  of  the 
crystalline  end-products  of  protein  decomposition  we  note  that  they  are 

1Kossel:  Zeit.  physiol.  Chem.,  44,  347,  1905. 
'Osborne  and  Guest:  Jour.  Biol.  Chem.,  9,  425,  1911. 
8  Abderhal4en,  Kossel  and  others. 

4  Abderhalden,  Fischer,  Morner  and  others. 

5  Fischer,  Levene  and  Aders:  Zeit.  physiol.  Chem.,  35,  70,  1902;  also  Levene  and  Beatty: 
Ibid.,  49,  252,  1906.    Dakin:  Jour.  Biol.  Chem.,  44,  449,  1920. 

•Abderhalden:  Zeit.  physiol.  Chem.,  37,  484,  1903. 

'Osborne  and  Liddle,  Am.  Jour.  Physiol.,  26,  295,  1910. 

'Osborne  and  Leaven  worth:  Unpublished  data  furnished  by  authors. 

"Osborne,  Van  Slyke,  Leavenworth  and  Vinograd:  Jour.  Biol.  Chem.,  22,  259,  1915. 

10  Roughly  estimated. 

11  Osborne  and  Liddle:  Am.  Jour  Physiol.,  26,  295,  1910. 

*  This  unique  and  important  protein  has  probably  been  more  carefully  analyzed  than 
any  other.  § 


PROTEINS 


67 


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a-amino-valeric 
acid. 

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pionic  acid. 

Lysine:  a-e-diami^o- 
caproic  acid. 

Histidine:  a  -  amino  -  /3  - 
imidazolyl  -  propionic 
acid. 

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carboxylic  acid.  . 

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a-  a  m  i  n  o-propionic- 
acid. 

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droxy-a-pyrrolidine 
carboxylic  acid. 

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methyl-j8-ethyl-pro- 
pionic  acid. 

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PHYSIOLOGICAL   CHEMISTRY 


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PROTEINS  69  , 

invariably  acids,  as  has  already  been  mentioned,  and  contain  an  NH2 
group  in  the  a  position.  This  relation  of  the  NH2  group  to  the  acid  radi- 
cal is  constant,  no  matter  what  other  groups  or  radicals  are  present.  We 
may  have  straight  chains  as  in  alanine  and  glutamic  acid,  the  benzene 
ring  as  in  phenylalanine,  or  we  may  have  sulphurized  bodies  as  in  cystine 
and  still  the  formula  is  always  of  the  same  type,  i.e., 

NH2 
R— CH— COOH 

It  is  seen  that  this  characteristic  grouping  in  the  amino  acid  provides 
each  one  of  these  ultimate  fragments  of  the  protein  molecule  with  both  a 
strong  acid  and  a  strong  basic  group.  For  this  reason  it  is  theoretically 
possible  for  a  large  number  of  these  amino  acidfc  to  combine  and  the  re- 
sulting combinations  may  be  very  great  in  number,  since  there  is  such 
a  varied  assortment  of  the  acids.  The  protein  molecule,  which  is  of 
such  mammoth  proportions,  is  probably  constructed  on  a  foundation  of 
this  sort.  Many  valuable  data  have  been  collected  regarding  the  syn- 
thetic production  of  protein  substances,  the  leaders  in  this  line  of  in- 
vestigation being  Fischer  and  Abderhalden.  After  having  gathered  a 
mass  of  data  regarding  the  final  products  of  the  protein  decomposition 
and  demonstrating  that  amino  acids  were  the  ultimate  results  of  the 
various  forms  of  decomposition,  these  investigators,  and  notably  Fis- 
cher, set  about  in  an  effort  to  form,  from  these  amino  acids,  by  syn- 
thetic means,  substances  which  should  possess  protein  characteristics. 
The  simplest  of  these  bodies  formed  in  this  way  was  synthesized  from 
two  molecules  of  glycocoll  with  the  liberation  of  water,  thus: 

H2N-CH2-CO   OH  H  HN-CH2-COOH. 

The  body  thus  formed  is  a  dipeptide,  called  glycyl-glycine.  In  an  analo- 
gous manner  may  be  produced  leucyl-leucine,  through  the  synthesis  of 
two  molecules  of  leucine  or  leucyl-alanyl-glycine  through  the  union  of  one 
molecule  of  leucine,  one  of  alanine,  and  one  of  glycocoll.  By  this  pro- 
cedure Fischer  and  his  pupils  have  been  able  to  make  a  large  number  of 
peptides  containing  varied  numbers  of  amino  acid  radicals,  the  name 
polypeptides  being  given  to  the  whole  group  of  synthetic  substances  thus 
formed.  One  of  the  most  complex  polypeptides  \yet  produced  is  one 
containing  fifteen  glycocoll  and  three  leucine  residues. 

Notwithstanding  the  fact  that  most  synthetic  polypeptides  are  pro- 
duced through  a  union  of  amino  acids  by  means  of  their  imide  bonds,  it 
must  not  be  imagined  that  the  protein  molecule  is  constructed  from 


70  PHYSIOLOGICAL  CHEMISTRY 

amino  acids  linked  together  in  straight  chains  in  a  manner  analogous  to 
the  formation  of  simple  peptides,  such  as  glycyl-glycine.  The  molecu- 
lar structure  of  the  proteins  is  much  too  complex  to  be  "explained  upon 
any  such  simple  formation  as  that.  There  must  be  a  variety  of  linkings, 
since  there  is  a  varied  assortment  of  decomposition  products  of  totally 
different  structure. 

Many  of  these  synthetic  bodies  respond  to  the  biuret  test,  are  pre- 
cipitated by  phosphotungstic  acid,  and  behave,  in  other  ways,  as  to 
leave  no  doubt  as  to  their  protein  characteristics.  For  instance,  a 
number  of  amino  acids  each  possessing  a  sweet  taste  have  been  syn- 
thesized in  such  a  manner  as  to  yield  a  polypeptide  of  bitter  taste,  a 
well-known  characteristic  of  peptones.  From  the  fact  that  the  poly- 
peptides  formed  in  the  manner  indicated  have  free  acidic  and  basic 
radicals  we  gather  the  explanation  of  the  amphoteric  character  of  true 
proteins. 

For  the  benefit  of  those  especially  interested  in  such  matters  a  photo- 
graph of  the  Fischer  apparatus  (Fig.  24,  page  74)  used  in  the  fractional 
distillation,  in  vacuo}  of  the  esters  of  the  decomposition  products  of  the 
proteins,  as  well  as  micro-photographs  and  drawings  of  preparations  of 
several  of  these  decomposition  products  (Figs.  21  to  33,  pages  71  to  83) 
are  introduced.  For  the  preparations  and  the  photograph  of  the  appa- 
ratus the  author  is  indebted  to  Dr.  T.  B.  Osborne,  of  New  Haven,  Conn., 
who  has  made  many  important  observations  upon  the  hydrolysis  of 
proteins.  The  reproduction  of  the  crystalline  form  of  some  of  the  more 
recent  of  the  products  may  be  of  interest  to  those  viewing  the  field  of 
physiological  chemistry  from  other  than  the  student's  aspect. 

An  extended  discussion  of  the  various  decomposition  products  being 
out  of  place  in  a  book  of  this  character,  we  will  simply  make  a  few  general 
statements  in  connection  with  the  primary  decomposition  products. 

DISCUSSION  OF  THE  PRODUCTS 

Ammonia,  NH3. — Ammonia  is  an  important  decomposition  product 
of  all  proteins  and  probably  arises  from  an  amide  group  combined 
with  a  carboxyl  group  of  some  of  the  amino  acids.  It  is  possible  that  the 
dibasic  acids,  aspartic  and  glutamic,  furnish  most  of  these  carboxyl 
groups.  This  is  indicated  by  the  more  or  less  close  relationship  which 
exists  between  the  amount  of  ammonia  and  that  of  the  dibasic  acids 
which  the  .several  proteins  yield  upon  decomposition.  The  elimination 
of  the  ammonia  from  proteins- under  the  action  of  acids  and  alkalis  is 
very  similar  to  that  from  amides  like  asparagine. 

Glycocoll  (glycine),  CH2(NH2)-COOH.— Glycocoll,  or  amino  acetic 


PROTEINS  71 

acid,  is  the  simplest  of  the  ammo  acids  which  occurs  as  a  protein  de- 
composition product1  and  has  the  following  formula:] 

NH2 
H— C— COOH. 


Glycocoll,  as  the  formula  shows,  contains  no  asymmetric  carbon  atom, 
and  is  the  only  amino  acid  yielded  by  protein  decomposition  which  is 
optically  inactive.  Glycocoll  and  leucine  were  among  the  first  decom- 
position products  of  proteins  to  be  discovered.  Upon  administering 
benzoic  acid  to  man  or  lower  animals  the  output  of  hippuric  acid  in  the 


FIG.  21. — GLYCOCOLL  ESTER  HYDROCHLORIDE. 

urine  is  greatly  increased,  thus  showing  a  synthesis  from  benzoic  acid  and 
glycocoll  in  the  organism  (see  page  619,  Chapter  XXVIII).  Glycocoll, 
ingested  in  small  amount,  is  excreted  in  the  urine  as  urea,  whereas  if 
administered  in  excess  it  appears  in  part  unchanged  in  the  urine.  It  is 
usually  separated  from  the  mixture  of  protein  decomposition  products 
as  the  hydrochloride  of  the  ester.  The  crystalline  form  of  this  com- 
pound is  shown  in  Fig.  21. 

Alanine,  CH3-CH(NH2)-COOH. — Alanine  is  a-amino-propionic  acidt 
and  as  such  it  may  be  represented  structurally  as  follows: 

H    NH2 
H— C— C— COOH. 

1 1 ;  H  i 

1  Amino Jorrnic  acid  (carbamic  acid),  NH2-COOH,  is  the  simplest  amino  acid. 


72  PHYSIOLOGICAL  CHEMISTRY 

Obtained  from  protein  substances,  alanine  is  dextro-rotatory,  is  very 
soluble  in  water,  and  possesses  a  sweet  taste.  Tyrosine,  phenylalanine, 
cystine,  and  serine  are  derivatives  of  alanine.  This  amino  acid  has  been 
obtained  from  nearly  all  proteins  examined.  Its  absence  from  those 
proteins  from  which  it  has  not  been  obtained  has  not  been  proven. 
Most  proteins  yield  relatively  small  amounts  of  alanine. 

Serine,  CH2(OH)-CH(NH2)-COOH.-- Serine  is  a-amino-p-hydroxy- 
propionic  acid  and  possesses  the  following  structural  formula: 

OHNH2 

I      I 
H— C— C— COOH. 

I.     I 
H    H 

Serine  obtained  from  proteins  is  levo-rotatory,  possesses  a  sweet  taste, 
and  is  quite  soluble  in  water.  Serine  is  not  obtained  in  quantity  from 


FIG.  22. — SERINE. 

most  proteins,  but  is  yielded  abundantly  by  silk  glue.  Owing  to  the 
difficulty  of  separating  serine  it  has  not  been  found  in  a  number  of 
proteins  in  which  it  probably  occurs.  Serine  crystals"  are  shown  in  Fig. 
22. 

Phenylalanine,  C6H5-CH2-CH(NH2)-COQH.— This  product  is  0- 
phenyl-a-ami^o-propionic  acid,  and  may  be  represented  graphically  as 
follows: 

H     NH2 

-C—  C—  COOH. 

I       I 
H    H 


PROTEINS 


73 


The  levo-rotatory  form  is  obtained  from  proteins.  Phenylalanine  has 
been  obtained  from  all  the  proteins  examined  except  from  the  pro- 
tamines  and  some  of  the  albuminoids.  The  yield  of  this  body  from  the 
decomposition  of  proteins  is  frequently  greater  than  the  yield  of  tyro- 
sine.  The  crystalline  form  of  phenylalanine  is  shown  in  Fig.  23. 

Tyrosine,  C6H4(OH)-CH2-CH(NH2)-COOH.— Tyrosine,  one  of  the 
first  discovered  end-products  of  protein  decomposition,  is  the  ammo 
acid,  a-amino-$-para-hydroxy-phenyl-propionic  acid  or  hydroxy  phenyl- 
alanine. It  has  the  following  formula. 

H     NH2 

I       I 
^C— C— COOH. 


H    H 


OH 


The  tyrosine  which  results  from  protein  decomposition  is  usually  levo- 
rotatory.  Tyrosine  is  one  of  the  end-products  of  tryptic  digestion  and 
usually  separates  in  conspicuous  amount  early  in  the  process  of  diges- 


FIG.  23.— PHENYLALANINE. 

tion.     It  does  not  occur,  however,  as  an  end-product  of  the  decomposi- 
tion of  gelatin. 

Tyrosine  is  found  in  old  cheese,  and  derives  its  name  from  this  fact. 
It  crystallizes  in  tufts,  sheaves,  or  balls  of  fine  needles,  which  decompose 
at  095°C.  and  are  sparingly  soluble  in  cold  (1-2454)  water,  but  much 
more  so  in  boiling  (1-154)  water.  Tyrosine  forms  soluble  salts  with 
alkalis,  ammonia,  or  mineral  acids,  and  is  soluble  with  difficulty  in 
acetic  acid.  It  responds  to  Millon's  reaction,  thus  showing  the  presence 


74 


PHYSIOLOGICAL   CHEMISTRY 


of  the  hydroxyphenyl  group,  but  gives  no  other  protein  test.  The  aro- 
matic groups  present  in  tyrosine,  phenylalanine,  and  tryptophane  cause 
proteins  to  yield  a  positive  xanthoproteic  reaction.  In  severe  cases  of 
typhoid  fever  and  smallpox,  in  acute  yellow  atrophy  of  the  liver,  and  in 


FIG.  24. — FISCHER  APPARATUS. 

Reproduced  from  a  photograph  made  by  Prof.  E.  T.  Reichert,  of  the  University  of  Penn- 
sylvania. The  negative  was  furnished  by  Dr.  T.  B.  Osborne,  of  New  Haven,  Conn. 

At  Tank  into  which  freezing  mixture  is  pumped  and  from  which  it  flows  through  the 
condenser,  B;  C,  flask  from  which  the  esters  are  distilled,  the  distillate  being  collected  in  D\ 
E,  a  Dewar  flask  containing  liquid  air  serving  as  a  cooler  for  condensing  tube  F;  G  and  G', 
tubes  leading  to  the  Geryck  pump  by  which  the  vacuum  is  maintained;  /,  tube  leading  to  a 
McLeod  gauge  (not  shown  in  figure);  /,  a  bath  containing  freezing  mixture  in  which  the 
receiver  D  is  immersed;  K,  a  bath  of  water  during  the  first  part  of  the  distillation  and  of 
oil  during  the  last  part  of  the  process;  1-5,  stop  cocks  which  permit  the  cutting  out  of 
different  parts  of  the  apparatus  as  the  procedure  demands. 


acute  phosphorus  poisoning,  tyrosine  has  been  found  in  the  urine. 
Tyrosine  crystals  are  shown  in  Fig.  25,  page  75. 

Cystine,  C6Hi2O4N2S2. — Friedmann  has  shown  cystine  to  be 
di  (fi-thio-a-amino-propionic  acid)  and  to  possess  the  following  structural 
formula: 


PROTEINS 

CH2-S— S-CH2 

CH-NH2    CH-NH2. 

I  I 

COOH      COOH 


75 


FIG.  25. — TYROSINE. 

Cystine  is  the  principal  sulphur-containing  body  obtained  from  the 
decomposition  of  protein  substances.  It  is  obtained  in  greatest  amount 
as  a  decomposition  product  of  keratin-containing  tissues  as  horn,  hoof, 


FIG.  26. — CYSTINE. 


and  hair.  Cystine  occurs  in  small  amount  in  normal  urine  and  is 
greatly  increased  in  quantity  under  certain  pathological  conditions.  It 
crystallizes  in  thin,  colorless,  hexagonal  plates  which  are  shown  in  Fig. 


76  PHYSIOLOGICAL  CHEMISTRY 

26.     Cystine  is  very  slightly  soluble  in  water  but  its  salts,  with  both 
bases  and  acids,  are  readily  soluble  in  water.     It  is  levo-rotatory. 

It  was  formerly  claimed  that  cystine  occurred  in  two  forms,  i.e., 
stone-cystine  and  protein-cystine,  and  that  these  two  forms  are  distinct 
in  their  properties.  This  view  is  incorrect. 

For  the  preparation  of  cystine  from  wool  or  hair  see  page  86. 

For  a  discussion  of  cystine  sediments  in  urine  see  Chapter  XXV. 

Tryptophane,  C8H6N-CH2-CH(NH2)-COOH —Recently  Ellinger 
and  Flamand  have  shown  that  tryptophane  possesses  the  following 
formula: 

v_     GCH2-CH(NH2>COOH 

CH 
NH 

It  is  therefore  (3-indolyl-a-amino-propionic  acid.  Tryptophane  is  the 
mother-substance  oj  indole,  skatole-,  skatolyl  acetic  acid  and  skatolyl 
carboxylic  acid,  all  of  which  are  formed  as  secondary  decomposition 
products  of  proteins  (see  Chapter  XIII  on  Putrefaction  Products). 
Its  presence  in  protein  substances  may  be  shown  by  means  of  the 
Hopkins-Cole  reaction  (see  page  98).  It  may  be  detected  in  a  tryptic 
digestion  mixture  through  its  property  of  giving  a  violet  color  reaction 
with  bromine  water.1  Tryptophane  is  yielded  by  nearly  all  proteins, 
but  has  been  shown  to  be  entirely  absent  from  zein,  the  prolamin  (alcohol- 
soluble  protein)  of  maize,  and  also  from  gelatin. 

According  to  Osborne  and  Mendel,2  tryptophane  is  present  in  maxi- 
mum amount  in  lactalbumin.  Upon  being  heated  to  285°C.  trypto- 
phane decomposes  with  the  evolution  of  gas. 

Histidine,  CsHs^-CHs-CHtN^-COOH.-- Histidine  is  a-amino-p- 
imidazolyl-propionic  acid  or  p-imidazolyl-alanine  with  the  following 
structural  formula: 

H    NH2 

I       I 
HC-    -C— C— C— COOH. 

I       I 
H    H 
HN        N 

\/  1  . 

CH  f 

The  histidine  obtained  from  proteins  is  levo-rotatory.  It  has  been 
obtained  from  all  the  proteins  thus  far  examined,  the  majority  of  them 
yielding  about  2.5  per  cent  of  the  amino  acid.  However^  about  n  per 

1  Kurajeff:  Zeit.  physiol.  Chem.,  36,  501,  1898-99. 

2 Osborne  and  Mendel:  Jour.  Biol.  Chem.,  20,  357,  1915.  v 


PROTEINS  77 

cent  was  obtained  by  Abderhalden  from  globin,  the  protein  constituent 
of  oxyhemoglobin,  and  about  13  per  cent  by  Kossel  and  Kutscher  from 
the  protamine  sturine. 

Crystals  of  histidine  dichloride  are  shown  in  Fig.  27. 

Knoop's  Color  Reaction  for  Histidine. — To  an  aqueous  solution  of  histidine 
or  a  histidine  salt  in  a  test-tube  add  a  little  bromine  water.  A  yellow  coloration 
develops  in  the  cold  and  upon  further  addition  of  bromine  water  becomes  perma- 
nent. If  the  tube  be  heated,1  the  color  will  disappear  and  will  shortly  be  re- 
placed by  a  faint  red  coloration  which  gradually  passes  into  a  deep  wine  red. 
Usually  black,  amorphous  particles  separate  out  and  the  solution  becomes 
turbid. 

The  reaction  cannot  be  obtained  in  solutions  containing  free  alkali. 
It  is  best  to  use  such  an  amount  of  bromine  as  will  produce  a  permanent 


V  - .;:  ;. 

FIG.  27. — HISTIDINE  DICHLORIDE. 

yellow  color  in  the  cold.  The  use  of  a  less  amount  of  bromine  than  this 
produces  a  weak  coloration,  whereas  an  excess  of  bromine  prevents  the 
reaction.  The  test  is  hot  very  delicate,  but  a  characteristic  reaction 
may  always  be  obtained  in  i  :  1000  solutions.  The  only  histidine  de- 
rivative which  yields  a  similar  coloration  is  imidazolylethylamine,  and 
the  reaction  in  this  case  is  rather  weak  as  compared  with  the  color  ob- 
tained with  histidine  or  histidine  salts. 

Valine,  C5HnNO2. — The  ammo-valeric  acid  obtained  from  proteins 
is  a-amino-isovaleric  acid,  and  as  such  bears  the  following  formula: 

CH3    NH2 

I  I 

H— C C— COOH. 

I          I 
CH3    H 

1  The  same  reaction  will  take  place  in  the  cold  more  slowly. 


78  PHYSIOLOGICAL  CHEMISTRY 

It  closely  resembles  leucine  in  many  of  its  properties,  but  is  more  soluble 
in  water.  It  is  a  difficult  matter  to  identify  valine  in  the  presence  of 
leucine  and  isoleucine  inasmuch  as  these  amino  acids  crystallize  together 
in  such  a  way  that  the  combination  persists  even  after  repeated  recrys- 
tallizations.  Valine  is  dextro-rotatory. 

Arginine,  C6Hi4N402. — Arginine  is  d-guanidine-a-amino-valeric  acid 
and  possesses  the  following  structural  formula: 

H    H    H     NH2 

I       I       I       I 
NH—  C— C—  C—  C—  COOH. 

I         I       I       I       I 
NH=C      H    H    H    H 

NH2 

It  has  been  obtained  from  every  protein  so  far  subjected  to  decomposi- 
tion. The  arginine  obtained  from  proteins  is  dextro-rotatory,  and  has 
pronounced  basic  properties,  reacts  strongly  alkaline  to  litmus,  and  forms 
stable  carbonates.  Because  of  these  facts,  Kossel  considers  arginine  to 
be  the  nucleus  of  the  protein  molecule.  It  is  obtained  in  widely  different 
amounts  from  different  proteins,  over  85  per  cent  of  certain  protamines 
having  been  obtained  in  the  form  of  this  amino  acid.  It  is  claimed  that 
in  the  ordinary jnetabolic  activities  of  the  animal  body  arginine  gives 
rise  to  urea.  While  this  claim  is  probably  true,  it  should,  at  the  same 
time,  be  borne  in  mind  that  the  greater  part  of  the  protein  nitrogen  is 
eliminated  as  urea  and  that,  therefore,  but  a  very  small  part  can  arise 
from  arginine. 

Leucine,  CeHi3NO2. — Leucine  is  an  abundant  end-product  of  the 
decomposition  of  protein  material,  and  was  one  of  the  first  of  these 
products  to  be  discovered.  It  is  a-amino-isobutyl-acetic  aad,jtand 
therefore  has  the  following  formula. 

CH3     NH2 

I  I 

H—  C.CH2-C—  COOH. 

I  I 

CH3    H 

The  leucine  which  results  from  protein  decomposition  is  /-leucine. 
Leucine  is  present  normally  in  the  pancreas,  thymus,  thyroid,  spleen, 
brain,  liver,  kidneys,  and  salivary  glands.  It  has  been  found  patholog- 
ically in  the  urine  (in  acute  yellow  atrophy  of  the  liver,  in  acute  phos- 
phorus poisoning,  and  in  severe  cases  of  typhoid  fever  and  smallpox), 
and  in  the  liver,  blood  and  pus. 

Pure  leucine  crystallizes  in  thin,  white,  hexagonal  plates.   „  Crystals 


PROTEINS 


79 


of  pure  leucine  are  reproduced  in  Fig.  28.  It  is  rather  easily  soluble  in 
water  (46  parts),  alkalis,  ammonia,  and  acids.  On  rapid  heating  to 
295°C.,  leucine  decomposes  with  the  formation  of  carbon  dioxide,  ammo- 
nia, and  amylamine.  Aqueous  solutions  of  leucine  obtained  from  pro- 
teins are  levo-rotatory,  but  its  acid  or  alkaline  solutions  are  dextro- 
rotatory. So-called  impure  leucine1  is  a  slightly  refractive  substance, 
which  generally  crystallizes  in  balls  having  a  radial  structure,  or  in 
aggregations  of  spherical  bodies,  Fig.  145,  Chapter  XXV. 

Isoleucine,  C6Hi3NO2. — Isoleucine  is  a-amino-0-methyl-p-ethyl-pro- 
pionic  acid,  and  possesses  the  following  structural  formula: 

CH3     NH2 

I  I 

H— C    -    C— COOH. 

I  I 

C2H6  H 


FIG.  28. — LEUCINE. 

This  amino  acid  was  discovered  by  Ehrlich  in  1903.  '  Its  presence  has 
been  established  among  the  decomposition  products  of  only  a  few  pro- 
teins, although  it  probably  occurs  among  those  of  many  or  most  of  them. 
Ehrlich  has  shown  that  the  d-amyl  alcohol  which  is  produced  by  yeast 
fermentation  originates  from  isoleucine  and  the  isoamylalcohol  origi- 
nates from  leucine.  Isoleucine  is  dextro-rotatory. 

Lysine,  CH2(NH2)  •CH2-CH2-CH2-CH(NH2)  -COOH.— The  three 
bodies,  lysine,  arginine,  and  histidine,  are  frequently  classed  together 
as  the  hexone  bases.  Lysine  was  the  first  of  the  bases  discovered.  It 
is  a-€-diamino-caproic  acid  and  hence  possesses  the  following  structure. 

1  These  balls  of  so-called  impure  leucine  do  contain  considerable  leucine,  but  inasmuch 
as  they  may  contain  many  other  things  it  is  a  bad  practice  to  allude  to  them  as  leucine. 


8o 


PHYSIOLOGICAL   CHEMISTRY 

NH2H    H    H    NH2 

I       I       I       I       1 
— C— C— C— C— C— COOH 

I       I       I       I       I 
H    H    H    H    H 


FIG.  29. — LYSINE  PICRATE. 

It  is  dextro-rotatory  and  is  found  in  relatively  large  amount  in  casein 
and  gelatin.  Lysine  is  obtained  from  nearly  all  proteins,  but  is  absent 
from  the  vegetable  proteins  which  are  soluble  in  strong  alcohol.  It  is 


FIG.  30. — ASPARTIC  ACID. 

the  mother-substance  of  cadaverine  and  has  never  been  obtained  in 
crystalline  form.  Lysine  is  usually  obtained  -as  the  picrate  which  is 
sparingly  soluble  in  water  and  crystallizes  readily.  These  crystals;  are 
shown  in  Fig  29. 


PROTEINS  8 1 

Aspartic  Acid,  C4H7N04.— Aspartic  acid  is  amino-succinic  acid  and 
has  the  following  structural  formula: 

NH2 

H—  GCOOH 
H—  GCOOH. 

H 

The  amide  of  aspartic  acid,  asparagine,  is  very  widely  distributed 
in  the  vegetable  kingdom.     Asparagine  has  the  following  formula: 

NH2 

I 
H—  GCOOH 

H— GCO(NH2). 
H 

The  crystalline  form  of  aspartic  acid  is  exhibited  in  Fig.  30. 

Aspartic  acid  has  been  found  among  the  decomposition  products  of 
all  the  proteins  examined,  except  the  protamines.  It  has  not  been  ob- 
tained, however,  in  very  large  proportion  from  any  of  them.  The 
aspartic  acid  obtained  from  protein  is  levo-rotatory. 

Glutamic  Acid,  CsHgNO^ — This  acid  is  a-amino-normal-gliUaric 
acid  and  as  such  bears  the  following  graphic  formula: 

NH2 

H—  GCOOH 
H— C— H 
H— GCOOH. 

H 

Glutamic  acid  is  yielded  by  all  the  proteins  thus  far  examined, 
except  the  protamines,  and  by  most  of  these  in  larger  amount  than 
any  other  of  their  decomposition  products.  It  is  yielded  in  especially 
large  proportion  by  most  of  the  proteins  of  seeds,  43.66  per  cent  having 
been  obtained  by  Osborne  and  Guest1  by  the  hydrolysis  of  gliadin,  the 
prolamin  of  wheat.  This  is  the  largest  amount  of  any  single  decompo- 
sition product  yet  obtained  from  any  protein  except  the  protamines. 

1  Osborne  and  Guest:  Jour.  Biol.  Chem.,  9,  425, 
6 


82 


PHYSIOLOGICAL  CHEMISTRY 


Glutamic  acid  and  aspartic  acid  are  the  only  dibasic  acids  which 
have  thus  far  been  obtained  as  decomposition  products  of  proteins.  As 
there  is  an  apparent  relation  between  the  proportion  of  these  acids 
and  that  of  ammonia  which  the  different  proteins  yield  it  is  possible 
that  one  of  the  carboxyl  groups  of  these  acids  is  united  with  NH2  as 
an  amide,  the  other  carboxyl  group  being  united  in  polypeptide  union 
(see  page  70)  with  some  other  amino  acid.  This  might  be  represented 
by  the  following  formula: 

R— CHNH— COOH 

CO— CHNH2— CH2— CH2— CONHo. 

It  has  been  shown  by  Thierf elder  and  Sherwin1  that  the  amide, 
glutamine,  is  a  product  of  normal  metabolism  and  hence  this  substance 
rather  than  glutamic  acid  is  present  in  the  protein  molecule. 


FIG.  31. — GLUTAMIC  ACID. 

Reproduced  from  a  micro-photograph  made  by  Prof.  E.  T.  Reichert,  of  the  University 

of  Pennsylvania. 

The  glutamic  acid,  yielded  by  proteins  upon  hydrolysis,  is  dextro- 
rotatory. Crystals  of  glutamic  acid  are  reproduced  in  Fig.  31. 

Proline,  CsHgNO^ — Proline  is  a-pyrrolidine-carboxylic  acid  and 
possesses  the  following  graphic  structure: 

H2C        CH2 


H2C,      .CH-COOH. 
NH 

Proline  was  first  obtained  as  a  decomposition  product  of  casein.     Pro- 
^hierfelder  and  Sherwin:  Zeit.  Physiol.  Chemie.,  94, 1,  1915. 


PROTEINS 


line  obtained  from  proteins  is  levo-rotatory  and  is  the  only  protein  de- 
composition product  which  is  readily  soluble  in  alcohol.  It  is  also  one  of 
the  few  heterocyclic  compounds  obtained  from  proteins.  Proline  has 
been  found  among  the  decomposition  products  of  all  proteins  except  the 


FlG.   32. — LEVO-a-PROLINE. 

protamines.  The  maximum  yield  reported  is  13.73  Per  cent  obtained 
by  Osborne  and  Clapp  from  the  hydrolysis  of  hordein.  Fischer  and 
Boehner1  have  obtained  7.7  per  cent  from  the  hydrolysis  of  gelatin. 


FIG.  33. — COPPER  SALT  OF  PROLINE. 

Reproduced  from  a  micro-photograph  made  by  Prof.  E.  T.  Reichert,  of  the  University  of 

Pennsylvania. 

The  crystalline  form  of  hw-a-proline  is  shown  in  Fig.  32  and  the 
copper  salt  of  proline  is  represented  by  a  micro-photograph  in  Fig.  33. 
The  crystals  of  the  copper  salt  have  a  deep  blue  color,  but  when  they 
Fischer  and  Boehner:  Zeit.  phys.  chem.,  65,  118,  1910. 


84  PHYSIOLOGICAL   CHEMISTRY 

lose  their  water  of  crystallization  they  assume  a  characteristic  violet 
color. 

Hydroxyproline,  CgHgNOs. — Hydroxyproline  was  discovered  by 
Fischer.  It  has  as  yet  been  obtained  from  only  a  few  proteins,  but  this 
may  be  due  to  the  fact  that  only  a  few  have  been  examined  for  its  pres- 
ence. The  position  of  the  hydroxyl  group  has  not  yet  been  established. 

Diaminotrihydroxydodecanoic  Acid,  Ci2H26N205. — This  amino  acid 
was  discovered  by  Fischer  and  Abderhalden  as  a  product  of  the  hydro- 
lysis of  casein.  It  has  thus  far  been  obtained  from  no  other  source. 
It  is  levo-rotatory  and  its  constitution  has  not  been  determined. 

EXPERIMENTS 

Protein  Decomposition. — While  the  ordinary  courses  in  physiological 
chemistry  preclude  any  extended  study  of  the  decomposition  products 
of  proteins,  the  manipulation  of  a  simple  decomposition  and  the  sub- 
sequent isolation  and  study  of  a  few  o.f  the  products  most  easily  and 
quickly  obtained  will  not  be  without  interest. l  To  this  end  the  student 
may  use  the  following  decomposition  procedure. 

Treat  the  protein  (coagulated  egg  albumin)  in  a  large  flask  with  water  con- 
taining 3-5  per  cent  of  H2SO4  and  place  it  on  a  water-bath  until  the  protein  ma- 
terial has  been  decomposed  and  there  remains  a  fine,  fluffy,  insoluble  residue. 
Filter  off  this  residue  and  neutralize  the  filtrate  with  Ba(OH)2  and  BaCO8. 
Filter  off  the  precipitate  of  BaSO4  which  forms  and  when  certain  that  the  fluid  is 
neutral  or  faintly  acid,2  concentrate  (first  on  a  wire  gauze  and  later  on  a  water- 
bath)  to  a  syrup.  This  syrup  contains  the  end-products  of  the  decomposition  of 
the  protein,  among  which  are  proteoses,  peptones,  tyrosine,  leucine,  etc.  Add 
95  per  cent  alcohol  slowly  to  the  warm  syrup  until  no  more  precipitate  forms, 
stirring  continuously  with  a  glass  rod.  This  precipitate  consists  of  proteoses  and 
peptones.  Gather  the  sticky  precipitate  on  the  rod  or  the  sides  of  the  dish  and, 
after  warming  the  solution  gently  for  a  few  moments,  filter  it  through  a  filter 
paper  which  has  not  been  previously  moistened.  After  dissolving  the  precipi- 
tate of  proteoses  and  peptones  in  water3  the  solution  may  be  treated  according  to 
the  method  of  separation  given  on  page  119. 

The  leucine  and  tyrosine,  etc.,  are  in  solution  hi  the  warm  alcoholic  filtrate. 
Concentrate  this  filtrate  on  the  water-bath  to  a  thin  syrup,  transfer  it  to  a  beaker, 
and  allow  it  to  stand  over  night  in  a  cool  place  for  crystallization.  The  tyrosine 
first  crystallizes  (Fig.  25,  page  75),  followed  later  by  the  formation  of  characteristic 

1  The  procedure  here  set  forth  has  nothing  in  common  with  the  procedure  by  means 
of  which  the  long  line  of  decomposition  products  just  enumerated  are  obtained.  This 
latter  process  is  an  exceedingly  complicated  one  which  is  entirely  outside  the  province  of 
any  course  in  physiological  chemistry. 

9  If  the  solution  is  alkaline  in  reaction  at  this  point,  the  amino  acids  will  be  broken 
down  and  ammonia  will  be  evolved. 

3  At  this  point  the  aqueous  solution  of  the  proteoses  and  peptones  may  be  filtered  to 
remove  any  BaSO4  which  may  still  remain.  Tyrosine  crystals  will  also  be  found  here, 
since  it  is  less  soluble  than  the  leucine  and  may  adhere  to  the  proteose-peptone  precipitate. 
Add  the  crystals  of  tyrosine  to  the  warm  alcohol  nitrate.  v 


PROTEINS  85 

crystals  of  impure  leucine  (see  Fig.  145,  Chapter  XXV).  After  examining  these 
crystals  under  the  microscope,  strain  off  the  crystalline  material  through  fine 
muslin,  heat  it  gently  in  a  little  water  to  dissolve  the  leucine  (the  tyrosine  will  be 
practically  insoluble)  and  filter.  Concentrate  the  filtrate  and  allow  it  to  stand  hi  a 
cool  place  over  night  for  the  crude  leucine  to  crystallize.  Filter  off  the  crystals 
and  use  them  in  the  tests  for  leucine  given  on  page  86.  The  crystals  of  tyrosine 
remaining  on  the  paper  from  the  first  filtration  may  be  used  hi  the  tests  for  tyro- 
sine as  given  below.  If  desired,  the  tyrosine  and  leucine  may  be  purified  by 
recrystallizing  in  the  usual  manner.  Habermann  has  suggested  a  method  of 
separating  leucine  and  tyrosine  by  means  of  glacial  acetic  acid. 

EXPERIMENTS  ON  TYROSINE 

Make  the  following  tests  with  the  tyrosine  crystals  prepared  in 
the  above  experiments,  or  upon  those  obtained  during  the  preparation 
of  cystine  (see  page  86),  or  upon  some  pure  tyrosine  furnished  by  the 
instructor. 

1.  Microscopical  Examination. — Place  a  minute  crystal  of  tyrosine  on  a  slide, 
add  a  drop  of  water,  cover  with  a  cover-glass,  and  examine  microscopically. 
Now  run  more  water  under  the  cover-glass  and  warm  hi  a  Bunsen  flame  until  the 
tyrosine  has  dissolved.    Allow  the  solution  to  cool  slowly,  then  examine  again 
microscopically,  and  compare  the  crystals  with  those  shown  hi  Fig.  25,  page  75. 

2.  Solubility. — Try  the  solubility  of  very  small  amounts  of  tyrosine  hi  cold  and 
hot  water,  cold  and  hot  95  per  cent  alcohol,  dilute  NH4OH,  dilute  KOH  and  dilute 
HC1. 

3.  Sublimation. — Place  a  little  tyrosine  in  a  dry  test-tube,  heat  gently  and 
notice  that  the  material  does  not  sublime.    How  does  this  compare  with  the 
result  of  Experiment  3  under  Leucine? 

4.  Hoffman's  Reaction. — This  is  the  name  given  to  Millon's  reaction  when 
employed  to  detect  tyrosine.    Add  about  3  c.c.  of  water  and  a  few  drops  of  Mil- 
Ion's  reagent  to  a  little  tyrosine  in  a  test-tube.    Upon  dissolving  the  tyrosine  by 
heat  the  solution  gradually  darkens  and  may  assume  a  dark  red  color.    What 
group  does  this  test  show  to  be  present  hi  tyrpsine? 

5.  Sulphuric  Acid  Test  (Piria).— Warm  a  little  tyrosine  on  a  watch  glass  on  a 
boiling  water-bath  for  20  minutes  with  3-5  drops  'of  cone.  H2SO4.    Tyrosine- 
sulphuric  acid  is  formed  in  the  process.    Cool  the  solution  and  wash  it  into  a 
small  beaker  with  water.    Now  add  CaCO3  in  substance  slowly  with  stirring, 
until  the  reaction  of  the  solution  is  no  longer  acid.    Filter,  concentrate  the 
filtrate,  and  add  it  to  a  few  drops  (avoid  an  excess)  of  very  dilute  neutral  ferric 
chloride.    A  purple  or  violet  color,  due  to  the  formation  of  the  ferric  salt  of 
tyrosine-sulphuric  acid,  is  produced.    This  is  one  of  the  most  satisfactory  tests 
for  the  identification  of  tyrosine. 

6.  Formaldehyde-Sulphuric   Acid   Test    (Morner).— Add   about   3    c.c.   of 
MSrner's  reagent1  to  a  little  tyrosine  in  a  test-tube,  and  gently  raise  the  tempera- 
ture to  the  boiling-point.    A  green  color  results. 

1  Morner's  reagent  is  prepared  by  thoroughly  mixing  i  volume  of  formalin,  45  volumes 
of  distilled  water,  and  55  volumes  of  concentrated  sulphuric  acid. 


86  PHYSIOLOGICAL  CHEMISTRY 

7.  Folin  and  Denis's  Test.1 — To  1-2  c.c.  of  the  solution  to  be  tested  add  an 
equal  volume  of  a  special  reagent  (containing  10  per  cent  sodium  tungstate,  2 
per  cent  phosphomolybdic  acid  and  10  per  cent  phosphoric  acid)  and  3-10  c.c. 
of  a  saturated  solution  of  sodium  carbonate.  A  blue  color  indicates  tyrosine. 
It  is  said  to  detect  i  part  in  one  million. 

Abderhalden2  claims  the  reagent  also  reacts  with  tryptophane, 
oxytryptophane  and  /-oxyproline. 

EXPERIMENTS  ON  LEUCINE 

Make  the  following  tests  upon  the  leucine  crystals  already  prepared 
or  upon  some  pure  leucine  furnished  by  the  instructor. 

i,  2  and  3.  Repeat  these  experiments  according  to  the  directions  given 
under  Tyrosine  (pages  85  and  86). 

PREPARATION  OF  CYSTINE  3 

From  50  to  500  grams  of  wool  or  hair  is  pushed  into  a  (Jena)  flask  and  con- 
centrated hydrochloric  acid  (200  c.c.  to  each  100  grams  of  wool)  is  added.  In 
order  to  get  a  part  of  the  acid  quickly  to  the  bottom  of  the  flask  a  part  of  the  acid 
may  be  put  hi  first,  then  the  wool,  and  finally  the  remaining  acid.  A  condenser 
consisting  only  of  a  glass  tube  2  to  3  ft.  long  is  inserted  and  the  mixture  is  boiled 
until  the  biuret  reaction  is  entirely  negative.  The  wool  dissolves  hi  a  few  min- 
utes and  if  much  cystine  is  desired  more  wool  and  acid  can  then  be  introduced. 
After  three  to  five  hours*  boiling  with  moderate  quantities  of  wool  the  biuret 
reaction  has  usually  disappeared. 

To  the  hot  acid  solution  of  amino  acids  so  obtained  is  added  at  once  an  excess 
of  solid  sodium  acetate,  i.e.,  until  the  Congo  red  reaction  for  mineral  acids  is 
entirely  negative.  A  dark,  heavy  precipitate  containing  practically  all  the  cystine 
is  obtained.  After  a  few  hours*  standing  at  room  temperature  the  liquid  is  filtered 
off  and  the  precipitate  is  washed  with  cold  water.  (From  the  mother  liquor 
diluted  with  the  wash  water  is  usually  obtained  on  long  standing  a  second  pre- 
cipitate consisting  chiefly  of  tyrosine.) 

The  crude  cystine  is  then  dissolved  in  boiling  3-5  per  cent  hydrochloric  acid 
and  the  solution  is  decolorized  with  good  boneblack  which  should  have  been 
previously  thoroughly  digested  with  hot,  dilute  hydrochloric  acid  and  then  washed 
with  water  in  order  to  remove  the  calcium  phosphate.  The  hot  filtrate  from  the 
boneblack  should  be  as  clear  as  water.  If  it  is  not  perfectly  colorless  the  bone- 
black  treatment  should  be  repeated  and  if  a  colorless  solution  is  not  then  ob- 
tained the  fault  lies  with  the  quality  of  the  boneblack.  The  last  filtrate  is  heated 
to  boiling  and  the  cystine  precipitated  by  a  slow  addition  of  concentrated  hot 
sodium  acetate  solution. 

Large  amounts  of  colorless  cystine  consisting  of  typical  hexagonal  plates  can 
thus  be  prepared  without  difficulty  and  with  very  little  labor.  Compare  the 
microscopical  appearance  of  these  crystals  with  those  shown  hi  Fig.  26,  page  75. 

1  Folin  and  Denis:  Jour.  Biol.  Chem.,  12,  245,  1912. 

•Abderhalden:  Zeit.  Physiol.  Chem.,  85,  91,  1913. 

'Folin:  Jour.  Biol.  Chem.,  8,  9,  1910.  v 


PROTEINS 


THE  QUANTITATIVE  DETERMINATION  OF  ALIPHATIC 
AMINO  GROUPS 

Method  of  Van  Slyke.1 — Principle. — This  method  for  the  determination  of 
aliphatic  amino  nitrogen  is  based  on  the  measurement  of  the  nitrogen  gas  evolved 
in  the  reaction, 

RNHH-HNO2=ROH+N2+H20. 

During  the  process  the  following  reaction  also  takes  place,  the  nitrous  acid  solution 
decomposing  spontaneously  with  the  formation  of  nitric  oxide. 

2HNO2=HNO3+NO. 


FIG.  34.— VAN  SLYKE  AMINO  NITROGEN 
APPARATUS. 


FIG.  35.— SECTION  or  VAN  SLYKE 
APPARATUS. 


This  latter  reaction  is  utilized  in  displacing  all  the  air  of  the  apparatus  with  nitric 
oxide.    The  amino  solution  is  then  introduced,  evolution  of  nitrogen  mixed  with 
nitric  oxide  resulting.    The  oxide  is  absorbed  with  alkaline  permanganate  solution 
and  the  pure  nitrogen  measured  in  a  special  gas  burette  shown  in  the  figure. 
Procedure.— The  determination  is  carried  out  in  three  stages: 
i.  Displacement  of  Air  by  Nitric  Oxide— Water  from  F  (see  Figs.  34  and  35), 
fills  the  capillary  leading  to  the  Hempel  pipette  and  also  the  other  capillary  as 
far  as  c.    Into  A  one  pours  a  volume  of  glacial  acetic  acid  sufficient  to  fill  one- 
1  Van  Slyke:  Jour.  Biol.  Chem.,  12,  275,  1912;  16,  121  and  125,  1913. 


88  PHYSIOLOGICAL   CHEMISTRY 

fifth  of  D.  For  convenience,  A  is  etched  with  a  mark  to  measure  this  amount. 
The  acid  is  run  into  D,  cock  c  being  turned  so  as  to  let  the  air  escape  from  D. 
Through  A  one  now  pours  sodium  nitrite  solution  (30  grams  NaN02  to  100  c.c. 
H2O)  until  D  is  full  of  solution  and  enough  excess  is  present  to  rise  a  little  above 
the  cock  into  A.  It  is  convenient  to  mark  A  for  measuring  off  this  amount  also. 
The  gas  exit  from  D  is  now  closed  at  c,  and,  a  being  open,  D  is  shaken  for'a  few 
seconds.  The  nitric  oxide,  which  instantly  collects,  is  let  out  at  c,  and  the  shaking 
repeated.  The  second  crop  of  nitric  oxide  which  washes  out  the  last  portions  of  air, 
is  also  let  out  at  c.  D  is  now  connected  with  the  motor  and  shaken  till  all  but  20  c.c. 
of  the  solution  have  been  displaced  by  nitric  oxide  and  driven  back  into  A .  A  mark 
on  D  indicates  the  20  c.c.  point.  One  then  closes  a  and  turns  c  and/  so  that  D  and 
F  are  connected.  The  above  manipulations  require  between  one  and  two  minutes. 

2.  Decomposition  of  the  Amino  Substance.— Of  the  amino  solution  to  be  analyzed 
10  c.c.  or  less,  as  the  case  may  be,  are  measured  off  in  B.    Any  excess  added  above 
the  mark  can  be  run  off  through  the  outflow  tube.    The  desired  amount  is  then  run 
into  D,  which  is  already  connected  with  the  motor,  as  shown  in  Fig.  34.      It 
is  shaken  when  a-amino  acids  are  being  analyzed  for  a  period  of  three  to  five 
minutes.    With  a-amino  acids,  proteins  or  partially  or  completely  hydrolyzed 
proteins,  we  find  that  at  the  most  five  minutes  vigorous  shaking  completes  the 
reaction.     Only  in  the  case  of  some  native  proteins  which,  when  deaminized  form 
unwieldy  coagula  that  mechanically  interfere  with  the  thorough  agitation  of  the 
mixture,  a  longer  time  may  be  required.     In  case  a  viscous  solution  is  being  analyzed 
and  the  liquid  threatens  to  foam  over  into  F}  B  is  rinsed  out  and  a  little  caprylic 
alcohol  is  added  through  it.     For  amino  substances  such  as  amino  purins,  requiting 
a  longer  time  than  five  minutes  to  react,  one  merely  mixes  the  reacting  solutions 
and  lets  them  stand  the  required  length  of  time,  then  shakes  about  two  minutes  to 
drive  the  nitrogen  completely  out  of  solution. 

When  it  is  known  that  the  solution  to  be  analyzed  is  likely  to  foam  violently, 
it  is  advisable  to  add  caprylic  alcohol  through  B  before  the  amino  solution.  B  is 
then  rinsed  with  alcohol  and  dried  with  ether  or  a  roll  of  filter  paper  before  it 
receives  the  amino  solution. 

3.  Absorption  of  Nitric  Oxide  and  Measurement  of  Nitrogen. — The  reaction  being 
completed,  all  the  gas  in  D  is  displaced  into  F  by  liquid  from  A  and  the  mixture  of 
nitrogen  and  nitric  oxide  is  driven  from  F  into  the  absorption  pipette.1    The  driving 
rod  is  then  connected  with  the  pipette  by  lifting  the  hook  from  the  shoulder  of  d  and 
placing  the  other  hook,  on  the  opposite  side  of  the  driving  rod,  over  the  horizontal 
lower  tube  of  the  pipette.    The  latter  is  then  shaken  by  the  motor  for  a  minute, 
which,  with  any  but  almost  completely  exhausted  permanganate  solutions,  com- 
pletes the  absorption  of  nitric  oxide.     The  pure  nitrogen  is  then  measured  in  F. 
During  the  above  operations  a  is  left  open,  to  permit  displacement  of  liquid  from  D 
as  nitric  oxide  forms  in  D. 

Blank  determinations,  performed  as  above  except  that  10  c.c.  of  distilled  water 
replaces  the  solution  of  amino  substance,  must  be  performed  on  every  fresh  lot 
of  nitrite  used.  Nitrite  giving  a  much  larger  correction  than  0.3  to  0.4  c.c.  should 
be  rejected. 

The  room  temperature  and  the  barometric  pressure  must  be  noted.     The 

lThe  solution  in  the  absorption  pipette  is  40  grams  KMnO<  and  25  grams  KOH  in 
a  liter. 


PROTEINS 


89 


MILLIGRAMS  OF  AMINO  NITROGEN  CORRESPONDING  TO  iC.C.  OF  NITRO- 
GEN GAS  AT  n°-3o°C.;  728-772  MM.  PRESSURE 


1 

728 

730 

732 

734 

736 

738 

740 

742 

744 

746 

748 

750 

t 

11° 

0.5680 

0.5695 

0.5510 

0.5725 

0.5745 

0.5760 

0.5775 

0-5790 

0.5805 

0.5820 

0.5840 

0.5855 

11° 

12° 

0.56S5iO.  5670  0.5685 

0.5700 

0.5720 

0.5735  0.575O  0.5765 

0.5780 

0.5795 

0.5815 

0.5830 

12° 

13° 

0.56300.5645  0.56600.5675  0.5695 

0.57i00.5725i0.57400.5755 

0.5770 

0.5785 

0.5805 

13° 

14° 

0.5605 

0.5620 

0.5635 

0.565010.5665 

0.5680 

0.57000.5715 

0.5730 

0.574510.5760 

0.5775 

14° 

15°    0.5580 

0.5595 

o.  561010.5625 

0  .  5640 

0.5655 

0.5670  0.5685 

0.5705 

0.5720 

0.5735 

0.5750 

15° 

16°    0.5555 

0.5570 

0.5585  0.5600 

0.5615  0.5630 

0.5645 

0.5660 

0.5675 

0.5690 

0.5710 

0.5725      16° 

17°    0.5525 

0.5540 

0.5555  0  5575 

0.5590 

0.5605 

0.562010.5635 

0.5650 

0.5665 

0.5680 

0.5695      17° 

18°    0.5500 

0.5515 

0.553010.5545 

0.5560 

0.5580 

0.559510.5610 

0.5625 

0.5640  0.5655 

0.5670 

18° 

19° 

0.5475 

0.5490 

0.5505  0.5520 

0.5535 

0.5550 

o.  5565)0.5580 

0.5595 

0.5610 

0.5630 

0.5645      19° 

20°    0.5445 

0.5400 

0.5475  0.5495 

0.5510 

0.5525 

0.5540 

0.5555 

0.5570 

0.5585 

0.5600 

0.5615 

20° 

21°     0.5420|0.5435 

0.54500.5465 

0.54800.5495 

0.5510 

0.5525 

0.5540 

0.5555 

0.5575 

0.5590      21° 

22°    0.5395  0.5410 

0.5425  0.54400.5455 

0.5470 

0.5485 

0.5500 

0.5515 

0.55300.5545 

0.5560      22° 

23° 

0.5365 

0.5380 

0.539510.5410 

0.5425 

0.5440 

0.5455 

0.5470 

0.5485 

0.55000.5515 

0.5530|     23° 

24° 

0.5335 

0.5350 

0.5365  0.5380 

0.5400 

0.5415 

0.54300.5445 

0,5460 

0.5475 

0.5490 

0.5505      24° 

25°    0.53100.5325 

0.53400.5355 

0.5370 

0.5385 

0.5400 

0.5415 

0.5430 

0.5445 

0.5460 

0.5475      25° 

26°   0.5260 

0.5295 

0.53100.5325 

0.5340 

0.5355 

0.5370 

0.5365 

o  .  5400 

0.5415 

0.5430 

0.5445      26° 

27°     0.5250 

0.5265 

0.5280  0.5295 

0.5310 

0.5325 

0.5340|0.5355 

0.5370 

0.5385 

0.5400 

O.S4IS      27° 

28° 

0.5220 

0.5235  0.5250  0.5265 

0.5280 

0.5295 

0.53100.5325 

0.5340 

0.5355 

0-5370 

0.5385      28° 

29° 

0.5195 

0.5210 

0.5220  0.5235 

0.5250 

0.5265 

0.5280 

0.5295 

0.5310 

0.5325 

0-5340 

0.5355  i     29° 

30° 

0.5160 

O.SI75 

0.5190 

0.5205 

0.5220 

0.5235 

0.5250 

0.5265 

0.5280 

0.5295 

0.5310 

0.5325 

30° 

t 

728 

730 

732 

734 

736 

738 

740 

742 

744 

746 

748 

750 

t 

t 

752 

754 

756 

758 

760 

762 

764 

766 

768 

770 

772 

1 

-  1 

11° 

0.5870 

0.5885 

0  .  5900 

0.5915 

0.5935 

0.5950 

0.5965J0.5980 

0.5995 

0.6010 

0.6030        ii° 

12° 

0.5845 

0.5860 

0.5875  0.5890 

0.5905 

0.5925 

0.59400.5955 

0.5970  0.5985J0.6000 

12° 

13° 

0.5820 

0.5835 

0.5850 

0.5865 

0.5880 

0.5895 

0.5910  0.5930 

0.5945  0.5960 

0.5975 

13° 

14° 

0.5790 

0.5805 

0.5825 

0.5840 

0.5855 

0.5870  0.5885  0.5900 

0.5915 

0.5935  0.5950 

14° 

15°, 

0.5765 

0.5765 

0.5795 

0.5810 

0.5830 

0.5845 

0.5860 

0.5875 

0.5890 

0.5905  0.5920 

15° 

16° 

0.5740 

0.5755 

0.5770 

0.5785 

0.5800 

0.5815 

0.5830 

0.5850 

0.5865 

0.5880 

0.5895 

16° 

17° 

0.5710 

0.5730 

0.5745 

0.5760 

0.5775 

0.5790 

0.5805  0.5820 

0.5825 

0.5850  0.5865 

17° 

1  8° 

0.5685 

O.5700 

0.5715 

0.5730 

0.5745 

0.5765 

0.57800.5795 

0.5810 

0.5825  0.5840 

1  8° 

19° 

0.5660 

0.5675 

0.5690 

0.5705|o.5720 

0.5735 

0.57500.5765 

0.5780 

0.5795  0.5810 

19° 

20° 

0.5630 

0.5645 

0.5660 

0.5675 

0.5690 

0.5705 

0.5725 

0.5740 

0.5755 

0.5770 

0.5785 

20° 

21° 

0.5605 

0.5620  0.5635 

0.5650 

0  .  5665 

0.5680 

0.5695 

0.5710 

0.5725 

0.5740 

0.5755 

21° 

22° 

0.5575 

0.55900.5605 

0.5620 

0.5635 

0.5650 

0.5665 

0.5680 

0  .  5695 

0.5715 

0.5730 

22° 

23° 

0.5545 

O.556oi0.5575 

0.5595 

0.5610 

0.5625 

0.5640J0.5655 

0.5670  0.5685 

0.5700 

23° 

24° 

0.5520 

0.5535  0.5550 

0.5565 

0.5580 

0.5595 

0.561010.5625 

0.5640  0.5655 

0.5670 

24° 

25° 

0.5490 

o.SSOS  0.5520 

0.5535 

0.5550 

0.5565 

0.5580  0.5595  0.561010.5625 

1              1         -  -  -     

0.5640 

25° 

26° 

0.5460 

0.5475 

0.5490 

0.5505 

0.5520 

0.5535 

0.5550 

0.5565  0.5580 

0.5595 

0.5610 

26° 

27° 

0.5430 

0.5445 

0.5460 

0.5475 

0.5490 

0.5505 

0.5520 

0.5535 

0.5550 

0.5565 

0.5580 

27° 

28° 

0.5400 

0.5415 

0  .  5430 

0.5445 

0.5460 

0.5475 

0.54900.5505 

0.5520 

0.5535 

0.5550 

28° 

29° 

0.5370 

0.5385 

0.5400 

0.5415 

0.5430 

0  .  5445 

0.5460  0.5475 

0.5490 

0.5505 

0.5520 

29° 

30° 

0.5340|0.535S 

0.5370 

0.5385 

0.5400 

0.54*5 

0.5430 

0.5445 

0.5460 

0.5475 

0.5490 

30° 

1 

752 

754 

756 

758 

760 

762 

764 

766 

768 

770 

"' 

t 

1  Journal    of    Biological    Chemistry,    12,    275,   1912.    Van  Slyke:  The    Quantitative 
Determination  of  Amino  Groups. 


QO  PHYSIOLOGICAL  CHEMISTRY 

calculation  of  the  weight  of  nitrogen  gas  corresponding  to  the  volume  obtained  is 
most  readily  made  with  the  aid  of  the  tables  (see  page  89)  devised  for  this  purpose.1 

The  Van  Slyke  Micro-apparatus.2 — In  later  work  Van  Slyke  has  used  to  a  large 
extent  an  apparatus  which  differs  from  the  one  described  above  only  in  being  con- 
siderably smaller.  More  accurate  measurements  can  be  made  with  this  and 
smaller  amounts  of  amino  nitrogen  determined.  In  using  this  only  10  c.c.  of 
nitrite  solution  and  2.5  c.c.  of  acetic  acid  are  required  for  an  analysis.  One-fifth 
the  amount  of  substance  may  be  analyzed  with  the  same  degree  of  accuracy  as 
with  the  larger  apparatus.  Practically  the  only  alteration  from  the  mode  of  opera- 
tion already  detailed  above,  is  in  the  speeds  at  which  the  deaminizing  bulb  and  the 
Hempel  pipette  are  shaken.  During  the  first  stage  of  the  analysis  the  deaminizing 
bulb  should  be  shaken  by  the  motor  at  a  very  high  rate  of  speed,  about  as  fast  as 
the  eye  can  follow  or  an  unnecessary  amount  of  time  is  lost  in  freeing  the  apparatus 
from  air.  This  stage  is  also  much  accelerated  by  warming  the  nitrite  solution  to 
30°  before  it  is  used,  in  case  a  low  room  temperature  has  reduced  the  temperature 
of  the  solutions  below  20°.  In  the  third  stage  when  the  nitric  oxide  is  being  ab- 
sorbed by  the  permanganate,  the  Hempel  pipette  should  be  shaken  not  faster  than 
twice  per  second.  This  is  to  prevent  the  breaking  off  of  small  gas  bubbles. 

It  is  especially  necessary  that  in  the  first  stage  the  removal  of  air  be  complete. 
This  is  assured  by  shaking  the  solution  in  the  deaminizing  bulb  back  each  time, 
in  this  stage,  until  the  bulb  is  two-thirds  filled  with  nitric  oxide. 

For  the  determination  of  total  and  free  amino  acid  nitrogen  in  the  urine  by 
this  method  see  chapter  on  Quantitative  Analysis  of  Urine. 

ESTIMATION  OF  AMINO-ACID  NITROGEN 

Method  of  Harding  and  MacLean.3 — Principle. — Ammo-acid  mixtures  when 
treated  with  triketohydrindene  hydrate  give  a  colored  solution  which  may  be  com- 
pared colorimetrically  with  a  standard. 

Procedure. — One  c.c.  of  the  solution  to  be  estimated  (containing  not  more  than 
0.05  mg.  of  amino-acid  of-nitrogen  and  neutral  to  phenolphthalein)  is  mixed  with 
i  c.c.  of  a  10  per  cent  aqueous  solution  of  pure  pyridine  and  i  c.c.  of  a  freshly  pre- 
pared 2  per  cent  solution  of  triketohydrindene  hydrate  and  heated  in  a  rapidly 
boiling  constant-level  water-bath  for  20  minutes.  At  the  end  of  that  time  the  test 
tube  is  removed,  cooled  and  diluted  to  a  suitable  volume,  usually  100  c.c.,  but  if  the 
amino-acid  a-nitrogen  is  very  small  in  amount  a  correspondingly  smaller  dilution 
can  be  used.  The  solution  is  compared  with  a  standard  in  a  Duboscq  colorimeter. 
The  standard  solution  is  prepared  by  dissolving  0.3178  gm.  of  pure,  freshly  crystal- 
lized alanine  in  a  liter  of  distilled  water.  The  solution  contains  0.05  mg.  of  N  per 
c.c.  Treat  i  c.c.  of  this  standard  just  as  above,  except  that  only  i  c.c.  of  trike- 
tohydrindene is  required.  The  standard  solution  is  stable  for  three  months. 
Amounts  of  amino  nitrogen  from  0.005  to  °-°5  mS-  mav  be  determined.  The 

1See  Van  Slyke:  Jour.  Biol.  Chem.,  12,  275,  1912  or  Gattermann:  Praxis  des  organis- 
chen  Chemikers,  ninth  edition.  In  using  the  tables  in  the  latter  work  or  similar  tables  it 
should  be  borne  in  mind  that  the  volume  of  nitrogen  gas  must  be  divided  by  two,  inasmuch 
as  only  one-half  of  the  nitrogen  collected  comes  from  the  amino  groups. 

1  Either  apparatus  may  be  obtained  from  Emil  Greiner,  45  Cliff  Street,  New  York,  or 
from  Robert  Goetze,  Leipzig.  Van  Slyke  has  recently  described  a  third  form  of  his  ap- 
paratus about  half  of  the  size  of  the  earlier  micro-apparatus.  This  has  a  more  accurate 
burette  so  that  the  gas  volumes  can  be  read  to  o.ooi  c.c.  (Van  Slyke:  Jour.  Biol.  Chem.t 
23,  407,  1915.) 

8  Harding  and  MacLean:  Jour.  Biol.  Chem.,  20,  217,  1915;  24,  503,  1916;  25,  319,  1916. 


PROTEINS  91 

method  is  inaccurate  for  cystine  and  has  not  yet  been  adapted  for  use  with  biolog- 
ical fluids  other  than  solutions  of  protein  hydrolysis  products  formed  by  acid  or 
tryptic  hydrolysis. 

Method  of  Kober  and  Sugiura.1 — Kober  and  Sugiura  have  devised  micro- 
chemical  methods  for  the  determination  of  a  and  j3-amino  acids  and  certain  deriva- 
tives in  products  of  protein  hydrolysis  and  other  mixtures  based  upon  the  property 
of  these  amino  acids  and  derivatives  of  dissolving  cupric  hydroxide  quantitatively 
in  neutral  or  slightly  alkaline  solution.  The  reaction  is  said  to  be  very  rapid  and 
sensitive.  See  original  articles  for  details. 

1  Kober  and  Sugiura:  J.  Am.  Ch.  Soc.,  35,  1546,  1913. 
Kober:  /.  Ind.  Eng.  Ch.,  9,  501,  1917. 


CHAPTER  V 

PROTEINS:  THEIR  CLASSIFICATION  AND 
PROPERTIES 

FROM  what  has  already  been  said  in  Chapter  IV  regarding  the 
protein  substances  it  will  be  recognized  that  the  grouping  of  the  diverse 
forms  of  this  class  of  substances  in  a  logical  manner  is  not  an  easy 
task.  The  fats  and  carbohydrates  may  be  classified  upon  the  funda- 
mental principles  of  their  stereo-chemical  relationships,  whereas  such  a 
system  of  classification  in  the  case  of  the  proteins  is  absolutely  im- 
possible since,  as  we  have  already  stated,  the  molecular  structure  of 
these  complex  substances  is  unknown.  Because  of  the  diversity  of 
standpoint  from  which  the  proteins  may  be  viewed,  relative  to  their 
grouping  in  the  form  of  a  logically  classified  series,  it  is  obvious  that 
there  is  an  opportunity  for  the  presentation  of  classifications  of  a  widely 
divergent  character.  The  fact  that  there  were  until  recent  years  at 
least  a  dozen  different  classifications  which  were  recognized  by  various 
groups  of  English-speaking  investigators  emphasizes  the  difficulties  in 
the  way  of  the  individual  or  individuals  who  would  offer  a  classification 
which  should  merit  universal  adoption.  Realizing  the  great  handi- 
cap and  disadvantage  which  the  great  diversity  of  the  protein  classifi- 
cations was  forcing  upon  the  workers  in  this  field,  the  Chemical  and 
Physiological  Societies  of  England  drafted  a  classification  which  ap- 
pealed to  these  groups  of  scientists  as  fulfilling  all  requirements  and 
presented  it  for  the  consideration  of  the  American  Physiological  Society 
and  the  American  Society  of  Biological  Chemists.  The  outcome  of 
this  has  been  that  there  are  now  only  two  protein  classifications  which 
are  recognized  by  English-speaking  scientists,  one  the  British  Classi- 
fication, the  other  the  American  Classification.  These  classifications 
are  very  similar  and  doubtless  will  ultimately  be  merged  into  a  single 
classification:  In  our  consideration  of  the  proteins  we  shall  conform 
in  all  details  to  the  American  Classification.  In  this  connection  we 
will  say,  however,  that  we  feel  that  the  English  Societies  have  strong 
grounds  for  preferring  the  use  of  the  term  sclero proteins  for  albu- 
minoids and  chromo proteins  for  hemoglobins.  The  two  classifications 
are  as  follows: 

92 


PROTEINS  93 

CLASSIFICATION  OF  PROTEINS  ADOPTED  BY  THE  AMERI- 
CAN PHYSIOLOGICAL  SOCIETY  AND  THE  AMERICAN 
SOCIETY  OF  BIOLOGICAL  CHEMISTS 

I.  SIMPLE  PROTEINS 

Protein  substances  which  yield  only  a-amino  acids  or  their  deriva- 
tives on  hydrolysis. 

(a)  Albumins. — Soluble  in  pure  water  and  coagulable  by  heat, 
e.g.,    ovalbumin   from   egg  white,    serum   albumin   from    blood   serum, 
lactalbumin  from  milk,  vegetable  albumins. 

(b)  Globulins. — Insoluble  in  pure  water  but  soluble  in  neutral 
solutions  of  salts  of  strong  bases  with  strong  acids,1  e.g.,  serum  globulin, 
ow globulin  from  egg  yolk,  edestin  from  hemp  seed,  amandin  from  almond 
and  peach  kernel,  and  other  vegetable  globulins. 

(c)  Glutelins. — Simple  proteins  insoluble  in  all  neutral  solvents,  but 
readily  soluble  in  very  dilute  acids  and  alkalis,2  e.g.,  glutenin  from  wheat. 

(d)  Alcohol-soluble  Proteins  (Prolamins).3— Simple  proteins  solu- 
ble in  70-80  per  cent  alcohol,  insoluble  in  water,  absolute  alcohol,  and 
other  neutral  solvents,*  e.g.,  zein  from  corn,  gliadin  from  wheat  and 
rye,  hordein  from  barley,  and  bynin  from  malt. 

(e)  Albuminoids. — Simple  proteins  possessing  a  similar  structure  to 
those  already  mentioned,  but  characterized  by  a  pronounced  insolubility 
in  all  neutral  solvents,5  e.g.,  elastin  from  ligament,  collagen  from  tendon, 
keratin  from  horn  and  hoof. 

(f)  Histones. — Soluble  in  water  and  insoluble  in  very  dilute  ammo- 
nia, and,  in  the  absence  of  ammonium  salts,  insoluble  even  in  excess  of 
ammonia;  yield  precipitates  with  solutions  of  other  proteins  andacoagu- 
lum  on  heating  which  is  easily  soluble  in  very  dilute  acids.     On  hydroly- 
sis they  yield  a  large  number  of  amino  acids  among  which  the  basic 
ones  predominate.    In  short,  histones  are  basic  proteins  which  stand 
between  protamines  and  true  proteins,  e.g.,  globin  from  hemoglobin, 
scombrone  from  mackerel  sperm,  thymus  his  tone. 

(g)  Protamines. — Simpler  polypep tides  than  the  proteins  included 
in  the  preceding  groups.     They  are  soluble  in  water,  uncoagulable  by 

1  The  precipitation  limits  with  ammonium  sulphate  should  not  be  made  a  basis  for  dis- 
tinguishing the  albumins  from  the  globulins. 

2  Such  substances  occur  in  abundance  in  the  seeds  of  cereals  and  doubtless  represent  a 
well-defined  natural  group  of  simple  proteins. 

3  The  name  prolamins  has  been  suggested  for  these  alcohol-soluble  proteins  by  Dr. 
Thomas  B.  Osborne  (Science,  1908,  xxviii,  p.  417).     It  is  a  very  fitting  term  inasmuch  as 
upon  hydrolysis  they  yield  particularly  large  amounts  of  proline  and^ammonia. 

4  The  subclasses  defined  (a,  6,  c,  dy}  are  exemplified  by  proteins  obtained  from  both 
plants  and  animals.    The  use  of  appropriate  prefixes  will  sufi&ce  to  indicate  the  origin  of 
the  compounds,  e.g.,  owglobulin,  /acJalbumin,  etc. 

6  These  form  the  principal  organic  constituents  of  the  skeletal  structure  of  animals  and 
also  their  external  covering  and  its  appendages.  This  definition  does  not  provide  for 
gelatin  which  is,  however,  an  artificial  derivative  of  collagen. 


94  PHYSIOLOGICAL  CHEMISTRY 

heat,  have  the  property  of  precipitating  aqueous  solutions  of  other  pro- 
teins, possess  strong  basic  properties  and  form  stable  salts  with  strong 
mineral  acids.  They  yield  comparatively  few  amino  acids,  among 
which  the  basic  ones  predominate.  They  are  the  simplest  natural 
proteins ,  e.g.,  salmine  from  salmon  sperm,  sturine  from  sturgeon  sperm, 
clupeine  from  herring  sperm,  scombrine  from  mackerel  sperm. 


H.  CONJUGATED  PROTEINS 

Substances  which  contain  the  protein  molecule  united  to  some  other 
molecule  or  molecules  otherwise  than  as  a  salt. 

(a)  Nucleoproteins. — Compounds  of  one  or  more  protein  molecules 
with  nucleic  acid,  e.g.,  cytoglobulin  from  cytoplasm,  nucleohistone  from 
nucleus. 

(b)  Glycoproteins. — Compounds  of  the  protein  molecule  with  a 
substance  or  substances  containing  a  carbohydrate  group  other  than  a 
nucleic  acid,  e.g.,  mucins  and  mucoids  (osseomucoid  from  bone,  tendomu- 
coid  from  tendon,  ichthulin  from  carp  eggs,  helicoprotein  from  snail}. 

(c)  Phosphoproteins. — Compounds  of  the  protein  molecule  with 
some,  as  yet  undefined,  phosphorus-containing  substances  other  than  a 
nucleic  acid  or  lecithin,1  e.g.,  casein  from  milk,  ovovitellin  from  egg 
yolk. 

(d)  Hemoglobins. — Compounds    of    the    protein    molecule    with 
hematin,  or  some  similar  substance,  e.g.,  hemoglobin  from  red   blood 
cells,  hemocyanin  from  blood  of  invertebrates. 

(e)  Lecithoproteins.- — Compounds   of   the  protein   molecule  with 
lecithins, 

m.  DERIVED  PROTEINS 

i.  PRIMARY  PROTEIN  DERIVATIVES 

Derivatives  of  the  protein  molecule  apparently  formed  through 
hydrolytic  changes  which  involve  only  slight  alteration  of  the  protein 
molecule. 

(a)  Proteans. — Insoluble  products  which  apparently  result  from 
the  incipient  action  of  water,  very  dilute  acids  or  enzymes,  e.g.,  myosan 
from  myosin,  edestan  from  edestin. 

(b)  Metaproteins. — Products  of  the  further  action  of  acids  and  alka- 
lis whereby  the  molecule  is  so  far  altered  as  to  form  products  soluble  in 

1  The  accumulated  chemical  evidence  distinctly  points  to  the  propriety  of  classifying 
the  phosphoproteins  as  conjugated  compounds,  i.e.,  they  are  possibly  esters  of  some  phos- 
phoric acid  or  acids  and  protein. 


PROTEINS  95 

very  weak  acids  and  alkalis  but  insoluble  in  neutral  fluids,  e.g.,  acid 
metaprotein  (acid  albuminate),  alkali  metaprotein  (alkali  albuminate). 

(c)  Coagulated  Proteins. — Insoluble  products  which  result  from 
(i)  the  action  of  heat  on  their  solutions,  or  (2)  the  action  of  alcohol  on 
the  protein. 

2.  SECONDARY  PROTEIN  DERIVATIVES1 

Products  of  the  further  hydrolytic  cleavage  of  the  protein  molecule. 

(a)  Proteoses. — Soluble  in  water,  non-coagulable  by  heat,  and 
precipitated  by  saturating  their  solutions  with  ammonium— or  zinc 
sulphate,2  e.g.,  protoproteose,  deutero protease. 

(b)  Peptones. — Soluble  in  water,  non-coagulable  by  heat,  but  not 
precipitated  by  saturating  their  solutions  with  ammonium  sulphate,3 
e.g.,  antipeptone,  amphopeptone. 

(c)  Peptides. — Definitely  characterized  combinations  of  two  or  more 
amino  acids,  the  carboxyl  group  of  one  being  united  with  the  amino 
group  of  the  other  with  the  elimination  of  a  molecule  of  water,4  e.g., 
dipeptides,  tripeptides,  tetrapeptides,  pentapeptides. 

CLASSIFICATION  OF  PROTEINS  ADOPTED  BY  THE  CHEM- 
ICAL AND  PHYSIOLOGICAL  SOCIETIES 
OF  ENGLAND 

I.  SIMPLE  PROTEINS 

1.  Protamines,  e.g.,  salmine,  clupeine. 

2.  Histones,  e.g.,  globin,  scombrone. 

3.  Albumins,  e.g.,  ovalbumin,  serum  albumin,  vegetable  albumins. 

4.  Globulins,  e.g.,  serum  globulin,  ovoglobulin,  vegetable  globulins. 

5.  Glutelins,  e.g.,  glutenin. 

6.  Alcohol-soluble  proteins,  e.g.,  zein,  gliadin. 

7.  Scleroproteins,  e.g.,  elastin,  keratin. 

8.  Phosphoproteins,  e.g.,  casein,  vitellin. 

II.  CONJUGATED  PROTEINS 

1.  Glucoproteins,  e.g.,  mucins,  mucoids. 

2.  Nucleopro  terns,  e.g.,  nucleohistone,  cytoglobulin. 

3.  Chromoproteins,  e.g.,  hemoglobin,  hemocyanin. 

1  The  term  secondary  protein  derivatives  is  used  because  the  formation  of  the  primary 
derivatives  usually  precedes  the  formation  of  the  secondary  derivatives. 

2  As  thus  denned,  this  term  does  not  strictly  cover  all  the  protein  derivatives  com- 
monly called  proteoses,  e.g.,  heteroproteose  and  dysproteose. 

3  In  this  group  the  kyrines  may  be  included.     For  the  present  it  is  believed  that^it  will 
be  helpful  to  retain  this  term  as  defined,  reserving  the  expression  peptide  for  the  simpler 
compounds  of  definite  structure,  such  as  dipeptides,  etc. 

4  The  peptones  are  undoubtedly  peptides  or  mixtures  of  peptides,  the  latter  term  being 
at  present  used  to  designate  those  of  definite  structure. 


96  PHYSIOLOGICAL  CHEMISTRY 

III.  PRODUCTS  or  PROTEIN  HYDROLYSIS 

1.  Infraproteins,   e.g.,   acid  infraprotein   (acid   albuminate)y  alkali 
infraprotein  (alkali  albuminate). 

2.  Proteoses,  e.g.,  protoproteose,  hetero protease,  deuteroproteose. 

3.  Peptones,  e.g.,  amphopeptone,  antipeptone. 

4.  Polypep tides,  e.g.,  dipeptides,  tripeptides,  tetrapeptides. 

CONSIDERATIONS  OF  THE  VARIOUS  CLASSES 
OF  PROTEINS 

SIMPLE  PROTEINS 

The  simple  proteins  are  true  protein  substances  which,  upon  hy- 
drolysis, yield  only  a-amino  acids  or  their  derivatives.  "Although 
no  means  are  at  present  available  whereby  the  chemical  individuality  of 
any  protein  can  be  established,  a  number  of  simple  proteins  have  been 
isolated  from  animal  and  vegetable  tissues  which  have  been  so  well 
characterized  by  constancy  of  ultimate  composition  and  uniformity  of 
physical  properties  that  they  may  be  treated  as  chemical  individuals 
until  further  knowledge  makes  it  possible  to  characterize  them  more 
definitely."  Under  simple  proteins  we  may  class  albumins,  globulins, 
glutelins,  prolamins,  albuminoids,  histones  and  protamines. 

ALBUMINS 

Albumins  constitute  the  first  class  of  simple  proteins  and  may  be 
defined  as  simple  proteins  which  are  coagulable  by  heat  and  soluble 
in  pure  (salt-free)  water.  Those  of  animal  origin  are  not  precipitated 
upon  saturating  their  neutral  solutions  at  3o°C.  with  sodium  chloride 
or  magnesium  sulphate,  but  if  a  saturated  solution  of  this  character 
be  acidified  with  acetic  acid  -the  albumin  precipitates.  All  albumins 
of  animal  origin  may  be  precipitated  by  saturating  their  solutions  with 
ammonium  sulphate.1  They  may  be  thrown  out  of  solution  by  the 
addition  of  a  sufficient  quantity  of  a  mineral  acid,  whereas  a  weak 
acidity  produces  a  slight  precipitate  which  dissolves  upon  agitating  the 
solution.  Metallic  salts  also  possess  the  property  of  precipitating  al- 
bumins, some  of  the  precipitates  being  soluble  in  excess  of  the  reagent, 
whereas  others  are  insoluble  in  such  an  excess.  Of  those  proteins 
which  occur  native  the  albumins  contain  the  highest  percentage  of  sul- 
phur, ranging  from  1.6  to  2.5  per  cent.  Some  albumins  have  been 

1  In  tliis  connection,  Osborne's  observation  that  there  are  certain  vegetable  albumins 
which  are  precipitated  by  saturating  their  solutions  with  sodium  chloride  or  magnesium 
sulphate  or  by  half-saturating  with  ammonium  sulphate,  is  of  interest. 


PROTEINS  97 

obtained  in  crystalline  form,  notably  egg  albumin,  serum  albumin,  and 
lactalbumin,  but  the  fact  that  they  may  be  obtained  in  crystalline  form 
does  not  necessarily  prove  them  to  be  chemical  individuals. 

GENERAL  COLOR  REACTIONS  OF  PROTEINS 

These  color  reactions  are  due  to  a  reaction  between  some  one  or 
more  of  the  constituent  radicals  or  groups  of  the  complex  protein  mole- 
cule and  the  chemical  reagent  or  reagents  used  in  any  given  test.  Not 
all  proteins  contain  the  same  groups  and  for  this  reason  the  various  color 
tests  will  yield  reactions  varying  in  intensity  of  color  according  to  the 
nature  of  the  groups  contained  in  the  particular  protein  under  examina- 
tion. Various  substances  not  proteins  respond  to  certain  of  these  color 
reactions,  and  it  is  therefore  essential  to  submit  the  material  under  ex- 
amination to  several  tests  before  concluding  definitely  regarding  its 
nature. 

TECHNIC  OF  THE  COLOR  REACTIONS 

i.  Millon's  Reaction. — To  5  c.c.  of  a  dilute  solution  of  egg  albumin1  in  a  test- 
tube  add  a  few  drops  of  Millon's  reagent.  A  white  precipitate  forms  which  turns 
red  when  heated. 

This  test  is  a  particularly  satisfactory  one  for  use  on  solid  proteins, 
in  which  case  the  reagent,  diluted  with  water  1:5,  is  added  directly 
to  the  solid  substance  and  heat  applied,  which  causes  the  substance  to 
assume  a  red  color.  Such  proteins  as  are  not  precipitated  by  mineral 
acids,  for  example  certain  of  the  proteoses  and  peptones,  yield  a  red 
solution  instead  of  a  red  precipitate. 

The  reaction  is  due  to  the  presence  of  the  hydroxy-phenyl  group, 
— CeH4OH,  in  the  protein  molecule  and  certain  non-proteins  such  as 
tyrosine,  phenol  (carbolic  acid)  and  thymol  also  respond  to  the  reaction. 
Inasmuch  as  the  tyrosine  grouping  is  the  only  hydroxyphenyl  grouping 
which  has  definitely  been  proven  to  be  present  in  the  protein  molecule  it 
is  evident  that  protein  substances  respond  to  Millon's  reaction  because  * 
of  the  presence  of  this  tyrosine  complex.  The  test  is  not  a  very  satis- 
factory one  for  use  in  solutions  containing  inorganic  salts  in  large 
amount,  since  the  mercury  of  the  Millon's  reagent2  is  thus  precipitated 
and  the  reagent  rendered  inert.  This  reagent  is  therefore  never  used 
for  the  detection  of  protein  material  in  the  urine.  If  the  solution  under 

1  This  egg  albumin  solution  may  be  prepared  by  beating  egg-white  with  6-10  volumes  of 
water.  The  precipitate  of  ovoglobulin  is  filtered  off  and  the  filtrate  used  in  the  tests. 

1  Millon's  reagent  consists  of  mercury  dissolved  in  nitric  acid  containing  some  nitrous 
acid.  It  is  prepared  by  digesting  one  part  (by  weight)  of  mercury  with  two  parts  (by 
weight)  of  HNOj  (sp.  gr.  1.42)  and  diluting  the  resulting  solution  with  two  volumes  of 
water. 


98  PHYSIOLOGICAL   CHEMISTRY 

examination  is  strongly  alkaline  it  should  be  neutralized  inasmuch  as 
the  alkali  will  precipitate  yellow  or  black  oxides  of  mercury. 

2.  Xanthoproteic  Reaction. — To  2-3  c.c.  of  egg  albumin  solution  in  a  test- 
tube  add  concentrated  nitric  acid.    A  white  precipitate  forms,  which  upon  heating 
turns  yellow  and  finally  dissolves,  imparting  to  the  solution  a  yellow  color. 
Cool  the  solution  and  carefully  add  ammonium  hydroxide,  potassium  hydroxide, 
or  sodium  hydroxide  hi  excess.    Note  that  the  yellow  color  deepens  into  an 
orange. 

This  reaction  is  due  to  the  presence  in  the  protein  molecule  of  the 
phenyl  group — C6H5,  with  which  the  nitric  acid  forms  certain  nitro 
modifications.  The  particular  complexes  of  the  protein  molecule 
which  are  of  especial  importance  in  this  connection  are  those  of  tyrosine, 
phenylalanine,  and  tryptophane.  The  test  is  not  a  satisfactory  one  for 
use  in  urinary  examination  because  of  the  color  of  the  end-reaction. 

3.  Glyoxylic  Acid  Reaction  (Hopkins-Cole).1 — Place  1-2  c.c.  of  egg  albumin 
solution  and  3  c.c.  of  glyoxylic  acid,  CHO.COOH  +  H2O  or  CH(OH)2COOH, 
solution  (Hopkins-Cole  reagent2)  in  a  test-tube  and  ml*  thoroughly.    In  a  second 
tube  place  5  c.c.  of  concentrated  sulphuric  acid.    Incline  the  tube  containing  sul- 
phuric acid  and  by  means  of  a  pipette  allow  the  albumin-glyoxylic  acid  solution 
to  flow  carefully  down  the  side.    When  stratified  hi  this  manner  a  reddish-violet 
color  forms  at  the  zone  of  contact  of  the  two  fluids. 

In  performing  the  test  on  a  solid  substance  employ  modification 
described  on  page  106. 

This  color  is  due  to  the  presence  of  the  tryptophane  group.  Gelatin 
does  not  respond  to  this  test.  For  formula  of  tryptophane  see  page 
76.  Benedict3  has  suggested  a  new  reagent  for  use  in  carrying  out 
the  Hopkins-Cole  reaction.4  Nitrates  (NaN03  and  KN03)  chlorates, 
nitrites,  or  excess  of  chlorides,  entirely  prevent  the  reaction  where- 
as formaldehyde  or  nitric  acid  interfere  somewhat.5  The  sulphuric 
acid  used  must  be  pure. 

1  Hopkins  and  Cole:  Journal  of  Physiology,  27,  418,  1902. 

^Hopkins-Cole  reagent  is  prepared  as  follows:  To  one  liter  of  a  saturated  solution  of 
oxalic  acid  add  60  grams  of  sodium  amalgam  and  allow  the  mixture  to  stand  until  the 
evolution  of  gas  ceases.  Filter  and  dilute  with  2-3  volumes  of  water. 

1  Benedict:  Journal  of  Biological  Chemistry,  6,  51,  1909. 

4  Benedict's  modified  Hopkins-Cole  reagent  is  prepared  as  follows:  Ten  grams  of  pow- 
dered magnesium  are  placed  in  a  large  Erlenmeyer  flask  and  shaken  up  with  enough  dis- 
tilled water  to  liberally  cover  the  magnesium.  •  Two  hundred  and  fifty  c.c.  of  a  cold,  satur- 
ated solution  of  oxalic  acid  is  now  added  slowly.  The  reaction  proceeds  very  rapidly  and 
with  the  liberation  of  much  heat,  so  that  the  flask  should  be  cooled  under  running  water 
during  the  addition  of  the  acid.  The  contents  of  the  flask  are  shaken  after  the  addition  of 
the  last  portion  of  the  acid  and  then  poured  upon  a  filter,  to  remove  the  insoluble  magnesium 
oxalate.  A  little  wash  water  is  poured  through  the  filter,  the  nitrate  acidified  with  acetic 
acid  to  prevent  the  partial  precipitation  of  the  magnesium  on  long  standing,  and  made  up  to 
a  liter  with  distilled  water.  This  solution  contains  only  the  magnesium  salt  of  glyoxylic 
acid. 

1  Mathewson:  Dissertation  (Columbia  Univ.),  Eschenbach  Publishing  Co.,  Easton,  Pa., 
1912.  Cole:  Practical  Physiological  Chemistry,  4th  Ed.,  1914. 


PROTEINS  99 

4.  Biuret  Test.— To  2-3  c.c.  of  egg  albumin  solution  in  a  test-tube  add  an 
equal  volume  of  concentrated  potassium  hydroxide  solution,  mix  thoroughly, 
and  add  slowly  a  very  dilute  (2-5  drops  in  a  test-tube  of  water)  copper  sulphate 
solution  until  a  purplish-violet  or  pinkish-violet  color  is  produced.  The  depth 
of  the  color  depends  upon  the  nature  of  the  protein;  proteoses,  and  peptones 
giving  a  decided  pink,  while  the  color  produced  with  gelatin  is  not  far  removed 
from  a  blue. 

This  reaction  is  given  by  those  substances  which  contain  two  amino 
groups  in  their  molecule,  these  groups  either  being  joined  directly 
together  or  through  a  single  atom  of  nitrogen  or  carbon.  The  amino 
groups  mentioned  must  either  be  two  CONH2  groups  or  one  CONH2 
group  and  one  CSNH2,  C(NH)NH2  or  CH2NH2  group.  It  follows 
from  this  fact  that  substances  which  are  non-protein  in  character  but 
which  contain  the  necessary  groups  will  respond  to  the  biuret  test. 
As  examples  of  such  substances  may  be  cited  oxamide, 

CONH2 

CONH2 

and  biuret, 

CONH2 

NH. 

/ 
CONH2 

The  test  derives  its  name  from  the  fact  that  this  latter  substance  which 
is  formed  on  heating  urea  to  i8o°C.  (see  page  392)  will  respond  to  the 
test.  Protein  material  responds  positively  since  there  are  two  CONH2 
groups  in  the  protein  molecule. 

According  to  SchifF  the  end-reaction  of  the  biuret  test  is  dependent 
upon  the  formation  of  a  copper-potassium-biuret  compound  (cupri- 
potassium  biuret  or  biuret  potassium  cupric  hydroxide).  This  sub- 
stance was  obtained  by  Schiff  in  the  form  of  long  red  needles.  It  has 
the  following  formula: 


OH 


K— NH2-CO 

I 
OH  OH 


TOO  PHYSIOLOGICAL   CHEMISTRY 

If  much  magnesium  sulphate  is  present  a  precipitate  of  magnesium 
hydroxide  forms  which  interferes  with  the  test.  If  considerable 
ammonium  sulphate  is  present  a  large  excess  of  alkali  must  be  used. 

Testing  Colored  Solutions  by  Biuret  Test.  —  If  the  color  of  the  solu- 
tion is  such  as  to  interfere  with  the  end-reaction  of  the  biuret  test, 
proceed  as  follows:  Make  the  solution  strongly  alkaline  with  potassium 
hydroxide  and  add  a  solution  of  copper  sulphate.  Shake  up  the  mixture 
with  alcohol  and  if  protein  is  present  the  alcohol  will  assume  the  typical 
biuret  coloration.  This  procedure  is  not  applicable  in  case  the  pigment 
of  the  original  solution  is  soluble  in  alcohol.  Excess  of  the  copper  salt 
need  not  be  avoided  in  this  test. 

Gies's  Biuret  Reagent.1  —  Gies  has  devised  a  reagent  for  use  in  the  biuret  test. 
This  reagent  consists  of  10  per  cent  KOH  solution,  to  which  25  c.c.  of  3  per  cent 
CuS04  solution  per  liter  has  been  added.  This  imparts  a  slight  though  distinct 
blue  color  to  the  clear  liquid.  This  reagent  is  of  material  assistance  in  performing 
the  biuret  test. 

Biuret  Paper  of  Kantor  and  Gies.  —  According  to  Kantor  and  Gies2  when 
filter  paper  is  immersed  in  the  above  reagent  and  subsequently  dried  it  forms  a 
very  satisfactory  "biuret  paper"  which  may  be  used  in  a  manner  analogous  to 
indicator  papers.  Moist  papers  may  be  used  in  the  examination  of  powders  which 
are  neutral  or  alkaline  in  reaction.  In  preparing  the  "biuret  paper,"  if  the  filter 
paper  is  left  for  a  sufficient  length  of  time  in  the  reagent  all  traces  of  the  copper 
sulphate  will  be  removed  from  the  solution. 

5.  Ring  Biuret  Test  (Posner).  —  This  test  is  particularly  satisfactory  for  use  on 
dilute  protein  solutions,  and  is  carried  out  as  follows.     To  some  dilute  egg  albumin 
in  a  test-tube  add  one-half  its  volume  of  potassium  hydroxide  solution.    Now  hold 
the  tube  in  an  inclined  position  and  allow  some  very  dilute  copper  sulphate  solution, 
made  as  suggested  on  page  99,  to  flow  down  the  side,  being  especially  careful  to 
prevent  the  fluids  from  mixing.     At  the  juncture  of  the  two  solutions  the  typical 
end-reaction  of  the  biuret  test  should  appear  as  a  colored  zone  (see  Biuret  Test, 
page  99). 

6.  The  Triketohydrindene  Hydrate  (Ninhydrin)   Reaction.  —  To    5   c.c.    of 
dilute  protein  solution  add  one-half  c.c.  of  a  o.i  per  cent  solution  of  triketo- 
hydrindene  hydrate,  heat  to  boiling  for  one  to  two  minutes  and  allow  to  cool. 
A  blue  color  develops  if  the  test  is  positive. 

This  test  gives  positive  results  with  proteins,  peptones,  peptides,  and  amino 
acids  which  possess  a  free  carboxyl  and  a-amino  group.  In  a  concentration  of 
i  per  cent  the  ammonium  salts  of  weak  acids  react  positively,  as  do  also  the 
ammonium  salts  of  strong  acids  in  very  high  concentration.  Certain  amines  also 
give  the  reaction.3 


Proceedings  of  Society  of  Biological  Chemists,  Journal  of  Biological  Chemistry, 
7,  60,  1910. 

2  Kantor  and  Gies:  Proc.  Soc.  Biol.  Chem.,  p.  n,  1910. 

3  Harding  and  Warnerford:  Jour.  Biol.  Chem.,  25,  319,  1916. 
Harding  and  MacLean:  Jour.  Biol.  Chem.,  25,  337,  1916. 


PROTEINS  101 

PRECIPITATION  REACTIONS  AND  OTHER  PROTEIN  TESTS 

There  are  three  forms  in  which  proteins  may  be  precipitated,  i.e., 
unaltered,  as  an  albuminate,  and  as  ah  insoluble  salt.  An  instance  of  the 
precipitation  in  a  native  or  unaltered  condition  is  seen  in  the  so-called 
salting-out  experiments.  Various  salts,  notably  (NH^SO^  ZnS04, 
MgS04,  Na2S04  and  NaCl,  possess  the  power,  when  added  in  solid  form 
to  certain  definite  protein  solutions,  of  rendering  the  menstruum  incap- 
able of  holding  the  protein  in  solution,  thereby  causing  the  protein  to  be 
precipitated  or  salted-out,  to  use  the  common  term.  Mineral  acids  and 
alcohol  also  precipitate  proteins  unaltered.  In  the  case  of  concentrated 
acids  the  protein  is  dissolved  in  the  presence  of  an  excess  of  acid  with 
the  formation  of  a  protein  salt.  Proteins  are  precipitated  as  albu- 
minates  when  treated  with  certain  metallic  salts,  and  precipitated  as 
insoluble  salts  when  weak  organic  acids  such  as  certain  of  the  alkaloidal 
reagents  are  added  to  their  solutions. 

If  certain  acids  (picric,  phosphotungstic,  phosphomolybdic,  tannic, 
or  chromic)  be  added  to  a  neutral  albumin  solution,  a  precipitate  of  an 
insoluble  protein  salt  occurs.  If,  however,  the  salts  of  these  acids  be 
added  no  precipitate  occurs.  The  addition  of  a  small  amount  of  acid, 
as  acetic  acid,  to  such  a  solution  will  cause  a  precipitate  to  form.1 

The  effect  of  the  addition  of  the  salts  of  the  heavy  metals  is  in  the 
first  instance  to  cause  a  precipitation  of  the  protein.  In  many  cases, 
however,  the  addition  of  an  excess  of  such  salts  causes  the  solution  of 
the  precipitate,  while  a  further  excess  may  cause  a  reprecipitation.  The 
precipitate  which  is  first  formed  in  a  protein  solution  by  the  addition 
of  the  salts  of  the  heavy  metals  may  be  redissolved  not  only  by  an 
excess  of  such  salts  but  by  an  excess  of  protein  as  well.2 

Colloidal  iron,  kaolin  and  alumina  cream  are  frequently  used  for 
removing  proteins  from  solution.  The  process  is  one  of  adsorption 
and  has  been  adapted  to  certain  quantitative  methods. 

It  is  generally  stated  that  globulins  are  precipitated  from  their  solu- 
tions upon  half  saturation  with  ammonium  sulphate  and  that  albumins 
are  precipitated  upon  complete  saturation  by  this  salt.  Comparatively 
few  exceptions  were  found  to  this  rule  until  proteins  of  vegetable  origin 
came  to  be  more  extensively  studied.  These  studies,  furthered  es- 
pecially by  Osborne  and  associates,  have  demonstrated  very  clearly 
that  the  characterization  of  a  globulin  as  a  protein  which  is  precipitated 
by  half  saturation  with  ammonium  sulphate,  can  no  longer  hold. 
Certain  vegetable  globulins  have  been  isolated  which  are  not  precipi- 

xMathews:  Amer.  Jour,  of  Physiology,  i,  445*  1898.  .       . 

2Pauli:  Hofmeister's  Beitrage,  6,  233,  1904-05;  Robertson:  Ergebmsse  der  Physiolo&e, 
10,  290,  1910. 


102  PHYSIOLOGICAL   CHEMISTRY 

tated  by  this  salt  until  a  concentration  is  reached  greater  than  that 
secured  by  half-saturation.  As  an  example  of  an  albumin  which  does 
not  conform  to  the  definition  of  an  albumin  as  regards  its  precipitation 
by  ammonium  sulphate  may  be  mentioned  the  leucosin  of  the  wheat 
germ,  which  is  precipitated  from  its  solution  upon  /^/-saturation  with 
ammonium  sulphate.  The  limits  of  precipitation  by  ammonium 
sulphate,  therefore,  do  not  furnish  a  sufficiently  accurate  basis  for  the 
differentiation  of  globulins  from  albumins.  It  has  further  been  deter- 
mined that  a  given  protein  which  is  precipitable  by  ammonium  sulphate 
cannot  be  "salted-out"  by  the  same  concentration  of  the  salt  under  all 
conditions. 

EXPERIMENTS 

1.  Influence  of  Concentrated  Mineral  Acids,  Alkalis  and  Organic  Acids. — 
Prepare  five  test-tubes  each  containing  5  c.c.  of  concentrated  egg  albumin  solu- 
tion.   To  the  first  add  concentrated  H2SO4,  drop  by  drop,  until  an  excess  of  the 
acid  has  been  added.    Note  any  changes  which  may  occur  in  the  solution.    Allow 
the  tube  to  stand  for  24  hours  and  at  the  end  of  that  period  observe  any  altera- 
tion which  may  have  taken  place.    Heat  the  tube  and  note  any  further  change 
which  may  occur.    Repeat  the  experiment  in  the  four  remaining  tubes  with 
concentrated  hydrochloric  acid,  concentrated  nitric  acid,  concentrated  potassium 
hydroxide  and  acetic  acid.    How  do  strong  mineral  acids,  strong  alkalis,  and 
strong  organic  acids  differ  in  their  action  toward  protein  solutions? 

2.  Precipitation  by  Metallic  Salts. — Prepare  six  tubes  each  containing  2-3 
c.c.  of  dilute  egg  albumin  solution.    To  the  first  add  mercuric  chloride,  drop  by 
drop  slowly,  until  an  excess  of  the  reagent  has  been  added,  noting  any  changes 
which  may  occur.    If  not  added  very  gradually  the  formation  of  the  precipitate 
may  not  be  noted,  due  to  its  solubility  in  excess  of  the  reagent.    Repeat  the  ex- 
periment with  lead  acetate,  silver  nitrate,  copper  sulphate,  ferric  chloride,  and 
barium  chloride,  using  very  dilute  solutions. 

Egg  albumin  is  used  as  an  antidote  for  lead  or  mercury  poisoning. 
Why?     Is  it  an  equally  good  antidote  for  the  other  metallic  salts  tested? 

3.  Precipitation  by  Alkaloidal  Reagents.— Prepare  six  tubes  each  containing 
2-3  c.c.  of  dilute  egg  albumin  solution.    To  the  first  add  picric  acid  drop  by  drop 
until  an  excess  of  the  reagent  has  been  added,  noting  any  changes  which  may 
occur.    Repeat  the  experiment  with  trichloracetic  acid,  tannic  acid,  phospho- 
tungstic  acid,  phosphomolybdic  acid,  and  potassio -mercuric  iodide.    Are  these 
precipitates  soluble  in  excess  of  the  reagent?    Acidify  with  hydrochloric  acid 
before  testing  with  the  last  three  reagents. 

4.  Nitric  Acid  Test  (Heller). — Place  5  c.c.  of  concentrated  nitric  acid  in  a 
test-tube,  incline  the  tube,  and  by  means  of  a  pipette  allow  the  dilute  albumin 
solution  to  flow  slowly  down  the  side.    The  liquids  should  stratify  with  the 
formation  of  a  white  zone  of  precipitated  albumin  at  the  point  of  juncture.    This 
is  a  very  delicate  test  and  is  further  discussed  on  page  439. 

J  An  apparatus  called  the  albumoscope  or  horismascope  has  been  devised  for  use 
in  the  tests  of  this  character  and  has  met  with  considerable  favor.  The  method  of 
using  the  albumoscope  is  described  on  p.  103.  The  instrument  is  shown  in  Fig. 
135,  p.  440. 


PROTEINS 


103 


Use  of  the  Albumoscope.—Thh  instrument  is  intended  to  facilitate  the  making  of 
"ring"  tests  such  as  HeUer's  and  Roberts'.  In  making  a  test  about  5  c.c.  of  the 
solution  under  examination  is  first  introduced  into  the  apparatus  through  the  larger 
arm  and  the  reagent  used  in  the  particular  test  is  then  introduced  through  the  capil- 
lary arm  and  allowed  to  flow  down  underneath  the  solution  under  examination. 
If  a  reasonable  amount  of  care  is  taken  there  is  no  possibility  of  mixing  the  two  solu- 
tions and  a  definitely  defined  white  "ring"  is  easily  obtained  at  the  zone  of  contact. 

5.  Nitric  Acid.— MgSO4  Test  (Roberts).— Place  5  c.c.  of  Roberts'  reagent1  in 
a  test-tube,  incline  the  tube,  and  by  means  of  a  pipette  allow  the  albumin  solu- 
tion to  flow  slowly  down  the  side.    The  liquids  should  stratify  with  the  formation 
of  a  white  zone  of  precipitated  albumin  at  the  point  of  juncture.    This  test  is  a 
modification  of  Heller's  ring  test  and  is  rather  more  satisfactory.    The  albumo- 
scope  may  also  be  used  in  making  this  test  (see  Fig.  135,  page  440). 

6.  Spiegler's  Ring  Test. — Place  5  c.c.  of  Spiegler's  reagent2  in  a  test-tube,  in- 
cline the  tube,  and  by  means  of  a  pipette  allow  5  c.c.  of  albumin  solution,  acidified 
with  acetic  acid,  to  flow  slowly  down  the  side.     A  white  zone  will  form  at  the  point 
of  contact.     This  is  an  exceedingly  delicate  test,  in  fact  too  delicate  for  ordinary 
clinical  purposes,  since  it  serves  to  detect  albumin  when  present  in  the  merest  trace 
(i :  250,000).     This  test  is  further  discussed  on  page  424. 

7.  Tanret's  Test. — To  5  c.c.  of  albumin  solution  in  a  test-tube  add  Tanret's 
reagent,3  drop  by  drop,  until  a  turbidity  or  precipitate  forms.     This  is  an  exceed- 
ingly delicate  test.     Sometimes  the  albumin  solution  is  stratified  upon  the  reagent 
as  in  Heller's  or  Roberts'  ring  tests.     In  urine  examination  it  is  claimed  by  Repiton 
that  the  presence  of  urates  lowers  the  delicacy  of  the  test.    Tanret  claims  that  the 
removal  of  urates  is  not  necessary  inasmuch  as  the  urate  precipitate  will  disappear 
on  warming  and  the  albumin  precipitate  will  not.     He  says,  however,  that  mucin 
interferes  with  the  delicacy  of  his  test  and  should  be  removed  by  acidification  with 
acetic  acid  and  filtration  before  testing  for  albumin. 

8.  Sodium  Chloride  and  Acetic  Acid  Test. — Mix  2  volumes  of  albumin  solu- 
tion and  i  volume  of  a  saturated  solution  of  sodium  chloride  in  a  test-tube,  acidify 
with  acetic  acid,  and  heat  to  boiling.    The  production  of  a  cloudiness  or  the 
formation  of  a  precipitate  indicates  the  presence  of  albumin. 

9.  Acetic  Acid  and  Potassium  Ferrocyanide  Test.— To  5  c.c.  of  dilute  egg 
albumin  solution  in  a  test-tube  add  5-10  drops  of  acetic  acid.    Mix  well  and 
add  potassium  ferrocyanide,  drop  by  drop,  until  a  precipitate  forms.    This  test 
is  very  delicate. 

Schmiedl  claims  that  a  precipitate  of  Fe(Cn)6K2Zn  or  Fe(Cn)6- 
Zn2,  is  formed  when  solutions  containing  zinc  are  subjected  to  this  test, 
and  that  this  precipitate  resembles  the  precipitate  secured  with  protein 

1  Roberts'  reagent  is  composed  of  i  volume  of  concentrated  HNO3  and  5  volumes  of  a 
saturated  solution  of  MgSO4. 

2  Spiegler's  reagent  has  the  following  composition: 

Tartaric  acid 20  grams. 

Mercuric  chloride . . . . 4o  grams. 

Sodium  chloride 5°  grams. 

Glycerol 100  grams. 

Distilled  water i°oo  grams.     t 

9  Tanret's  reagent  is  prepared  as  follows :  Dissolve  1.35  grams  of  mercuric  chloride  in  25 
c.c.  of  water,  add  to  this  solution  3.32  grams  of  potassium  iodide  dissolved  in  25  c.c.  of 
water,  then  make  the  total  solution  up  to  60  c.c.  with  water  and  add  20  c.c.  of  glacial  acetic 
acid  to  the  combined  solutions. 


104  PHYSIOLOGICAL   CHEMISTRY 

solutions.  In  the  case  of  human  urine  a  reaction  was  obtained  when 
0.000022  gram  of  zinc  per  cubic  centimeter  was  present.  Schmiedl 
further  found  that  the  urine  collected  from  rabbits  housed  in  zinc-lined 
cages  possessed  a  zinc  content  which  was  sufficient  to  yield  a  ready  re- 
sponse to  the  test.  Zinc  is  the  only  interfering  substance  so  far 
reported. 

10.  Salting-out  Experiments. — (a)  To  25  c.c.  of  egg  albumin  solution  in  a 
small  beaker  add  solid  ammonium  sulphate  to  the  point  of  saturation,  keeping 
the  temperature  of  the  solution  below  4o°C.    Filter,  test  the  precipitate  by 
Millon's  reaction  and  the  filtrate  by  the  biuret  test.    What  are  your  conclu- 
sions?    (b)  Repeat  the  above  experiment,  making  the  saturation  with  solid 
sodium  chloride.    How  does  this  result  differ  from  the  result  of  the  saturation 
with  ammonium  sulphate?    Add  2-3  drops  of  acetic  acid.    What  occurs? 

All  proteins  except  peptones  are  precipitated  by  saturating  their 
solutions  with  ammonium  sulphate.  Most  globulins  are  precipitated 
by  saturating  their  solutions  with  sodium  chloride  (see  Globulins, 
page  107);  serum  globulin,  however,  is  not  thus  precipitated.  If  the 
saturated  solution  is  subsequently  acidified,  all  proteins  except  peptones 
are  precipitated. 

Soaps  may  be  salted-out  in  a  similar  manner  (see  page  184). 

11.  Coagulation  or  Boiling  Test. — Heat  25  c.c.  of  dilute  egg  albumin  solution 
to  the  boiling-point  in  a  small  evaporating  dish.    The  albumin  coagulates.    Com- 
plete coagulation  may  be  obtained  by  acidifying  the  solution  with  3-5  drops  of 
acetic  acid1  at  the  boiling-point.    Test  the  coagulum  by  Millon's  reaction. 

The  acid  is  added  to  neutralize  any  possible  alkalinity  of  the  solu- 
tion, to  dissolve  any  substances  which  are  not  albumin  and  to  facilitate 
coagulation  (see  further  discussion  on  pages  116  and  441). 

12.  Coagulation  Temperature.— Prepare  four  test-tubes  each  containing  5  c.c. 
of  neutral  egg  albumin  solution.    To  the  first  add  i  drop  of  0.2  per  cent  hydro- 
chloric acid,  to  the  second  add  i  drop  of  0.5  per  cent  sodium  carbonate  solution, 
to  the  third  add  i  drop  of  10  per  cent  sodium  chloride  solution  and  leave  the 
fourth  neutral  in  reaction.    Partly  fill  a  beaker  of  medium  size  with  water  and 
place  it  within  a  second  larger  beaker  which  also  contains  water,  the  two  vessels 
being  separated  by  pieces  of  cork.    Fasten  the  four  test-tubes  compactly  together 
by  means  of  a  rubber  band,  lower  them  into  the  water  of  the  inner  beaker  and 
suspend  them,  by  means  of  a  clamp  attached  to  one  of  the  tubes,  in  such  a  manner 
that  the  albumin  solutions  shall  be  midway  between  the  upper  and  lower  sur- 
faces of  the  water.    In  one  of  the  tubes  place  a  thermometer  with  its  bulb  entirely 
beneath  the  surface  of  the  albumin  solution  (Fig.  36).    Gently  heat  the  water  in 
the  beakers,  noting  carefully  any  changes  which  may  occur  in  the  albumin  solu- 
tions and  record  the  exact  temperature  at  which  these  changes  occur.    The 
first  appearance  of  an  opacity  in  an  albumin  solution  indicates  the  commencement 
of  coagulation  and  the  temperature  at  which  this  occurs  should  be  recorded  as 
the  coagulation  temperature  for  that  particular  albumin  solution. 

1  Nitric  acid  is  often  used  in  place  of  acetic  acid  in  this  test.     In  case  nitric  acid  is  used, 
ordinarily  1-2  drops  are  sufficient. 


PROTEINS 


What  is  the  order  in  which  the  four  solutions  coagulate? 

Repeat  the  experiment,  adding  to  the  first  tube  i  drop  of  acetic  acid,  to  the 
second  i  drop  of  concentrated  potassium  hydroxide  solution,  to  the  third  2  drops 
of  a  10  per  cent  sodium  chloride  solution  and  leave  the  fourth  neutral  as  before. 

What  is  the  order  of  coagulation  here?    Why?    See  page  116. 

13.  Precipitation  by  Alcohol. — Prepare  three  test-tubes  each  containing 
about  10  c.c.  of  95  per  cent  alcohol.  To  the  first  add  i  drop  of  0.2  per  cent 
hydrochloric  acid,  to  the  second  i  drop  of  potas- 
sium hydroxide  solution  and  leave  the  third 
neutral  in  reaction.  Add  to  each  tube  a  few 
drops  of  egg  albumin  solution  and  note  the  re- 
sults. What  do  you  conclude  from  this  experi- 
ment? 


If  in  acid  or  neutral  solution  alcohol 
precipitates  proteins  unaltered,  but  if  al- 
lowed to  remain  under  alcohol  the  protein 
is  transformed.  The  "fixing"  of  tissues  for 
histological  examination  by  means  of  al- 
cohol is  an  illustration  of  the  application 
of  this  transformation  produced  by  alcohol. 
It  apparently  is  a  process  of  dehydration. 

14.  Crystallization  of  Egg  Albumin.1 — Care- 
fully remove  the  egg-white  from  a  number  of 
absolutely  fresh  eggs.2  Measure  the  volume  of 
the  egg-white  and  add  an  equal  volume  of  satur- 
ated ammonium  sulphate  a  small  portion  at  a 
time,  beating  the  mixture  vigorously  after  each 
addition.3  Filter  the  mixture  through  a  large 
pleated  filter  paper.4  Measure  the  volume  of 
the  filtrate.  To  100  c.c.  of  the  filtrate  add  very 
carefully  a  10  per  cent  solution  of  acetic  acid  from 
a  burette  being  certain  to  note  the  exact  volume 
of  the  acid  used.  The  acid  should  be  added  drop 


Frc-  ^'- 


by  drop,  the  albumin  mixture  being  gently  shaken 
during  the  process.  Add  acid  until  the  precipi- 
tate which  forms  at  each  addition  is  no  longer  dissolved  when  the  albumin  is 
shaken,  and  an  opalescent  mixture  is  secured.  (It  is  generally  rather  difficult 
to  determine  this  point,  inasmuch  as  suspended  air  bubbles  may  simulate  a 
precipitate.)  As  soon  as  the  solution  is  milky,  indicating  that  a  permanent  pre- 
cipitate has  formed,  run  in  from  the  burette  i  c.c.  of  the  acetic  acid.  This  should 
produce  a  heavy  white  precipitate.  Now  take  the  burette  reading  to  determine 
the  exact  volume  of  acid  used  in  the  treatment  of  100  c.c.  of  the  albumin  mixture. 

1  Hopkins  and  Pinkus:  Jour.  PhysioL,  23. 

2  If  not  perfectly  fresh  the  albumin  will  not  crystallize. 
1  Note  the  odor  of  ammonia.     What  causes  it? 

4  Sometimes  better  results  are  obtained  by  permitting  the  mixture  to  stand  several 
hours  before  filtering. 


IO6  PHYSIOLOGICAL   CHEMISTRY 

Calculate  the  exact  volume  of  acid  necessary  to  precipitate  the  remaining  portion 
of  the  original  albumin  mixture  and  add  this  calculated  quantity.  Mix  the  two 
portions  of  albumin  and  allow  to  stand  over  night.  Remove  a  drop  of  the  suspended 
material  to  a  slide  and  examine  microscopically.  Crystals  in  the  form  of  fine 
needles  will  be  observed.  This  is  the  crystallized  egg  albumin.  To  recrystallize, 
filter  off  the  crystals  and  dissolve  them  in  the  smallest  possible  volume  of  water. 
Filter,  and  to  the  filtrate  carefully  add  saturated  ammonium  sulphate  until  a  faint, 
permanent  precipitate  is  formed.  Allow  the  mixture  to  stand  several  hours  and 
examine  as  before.  The  crystals  of  albumin  should  be  somewhat  larger  than  when 
first  examined. 

The  above  method  may  also  be  used  for  crystallizing  serum  albumin  from  the 
fresh  blood  serum  of  the  horse,  mule  or  ass. 

15.  Preparation  of  Powdered  Egg  Albumin.— This  may  be  prepared  as  follows: 
Ordinary  egg-white  finely  divided  by  means  of  scissors  or  a  beater  is  treated  with 
4  volumes  of  water  and  filtered.     The  filtrate  is  evaporated  on  a  water-bath  at 
about  5o°C.  and  the  residue  powdered  in  a  mortar. 

1 6.  Tests  on  Powdered  Egg  Albumin. — With  powdered  albumin  prepared  as 
described  above  (by  yourself  or  furnished  by  the  instructor),  try  the  following 
tests : 

(a)  Solubility.— Test  the  solubility  of  the  albumin  in  water,  sodium  chloride, 
dilute  acid  and  alkali. 

(b)  Millon's  Reaction. 

(c)  Glyoxylic  Acid  Reaction   (Hopkins-Cole).— When  used  to  detect  the 
presence  of  protein  in  solid  form  this  reaction  should  be  conducted  as  follows : 
Place  5  c.c.  of  concentrated  sulphuric  acid  in  a  test-tube  and  add  carefully,  by 
means  of  a  pipette,  3-5  c.c.  of  Hopkins-Cole  reagent.    Introduce  a  small  amount 
of  the  solid  substance  to  be  tested,  agitate  the  tube  slightly,  and  note  that  the 
suspended  pieces  assume  a  reddish-violet  color,  which  is  the  characteristic  end- 
reaction  of  the  Hopkins-Cole  test ;  later  the  solution  will  also  assume  the  reddish- 
violet  color. 

(d)  Composition  Test.— Heat  some  of  the  dry  powder  in  a  dry  test-tube  in 
which  is  suspended  a  strip  of  moistened  red  litmus  paper  and  across  the  mouth  of 
which  is  placed  a  piece  of  filter  paper  moistened  with  lead  acetate  solution. 
As  the  powder  is  heated  it  chars,  indicating  the  presence  of  carbon ;  the  fumes  of 
ammonia  are  evolved,  turning  the  red  litmus  paper  blue  and  indicating  the  pres- 
ence of  nitrogen  and  hydrogen ;  the  lead  acetate  paper  is  blackened,  indicating 
the  presence  of  sulphur,  and  the  deposition  of  moisture  on  the  side  of  the  tube 
indicates  the  presence  of  hydrogen.    Moisture  indicates  hydrogen  only  in  case 
both  powder  and  test-tube  used  in  the  test  are  absolutely  dry. 

(e)  Coagulation  Test. — Immerse  a  dry  test-tube  containing  a  little  powdered 
egg  albumin  in  boiling  water  for  a  few  moments.    Remove  and  test  the  solubility 
of  the  albumin  according  to  the  directions  given  under  (a)  above.    It  is  still 
soluble.    Why  -has  it  not  been  coagulated?    Repeat  the  above  experiments 
with  powdered  serum  albumin  and  see  how  the  results  compare  with  those 
just  obtained. 

;  SULPHUR  IN  PROTEIN 

Sulphur  is  believed  to  be  present  in  two  different  forms  in  the  pro- 
tein molecule.     The  first  form,  which  is  present  in  greatest  ^amount, 


PROTEINS  107 

is  that  loosely  combined  with  carbon  and  hydrogen.  An  example  of 
this  combination  is  shown  in  cystine, 

CH2-S— S-CH2 

I  I 

CH-NH2    CH-NH2 

COOH      COOH 

Sulphur  in  this  form  is  variously  termed  unoxidized,  loosely  combined,, 
mercaptan,  and  lead-blackening  sulphur.  The  second  form  is  combined 
in  a  more  stable  manner  with  carbon  and  oxygen  and  is  known  as 
oxidized  or  acid  sulphur.  The  protamines  are  the  only  class  of  sulphur- 
free  proteins. 

TESTS  FOR  SULPHUR, 

1.  Tests  for  Unoxidized  Sulphur.— (a)  To  equal  volumes  of  KOH  and  egg 
albumin  solutions  in  a  test-tube  add  1-2  drops  of  lead  acetate  solution  and  boil  the 
mixture.    Unoxidized  sulphur  is  indicated  by  a  darkening  of  the  solution,  the 
color  deepening  into  a  black  if  sufficient  sulphur  is  present.    Add  hydrochloric 
acid  and  note  the  characteristic  odor  evolved  from  the  solution.    Write  the  reac- 
tions for  this  test,     (b)  Place  equal  volumes  of  KOH  and  egg  albumin  solutions 
in  a  test-tube  and  boil  the  mixture  vigorously.    Cool,  make  acid  with  glacial 
acetic  acid  and  add  1-2  drops  of  lead  acetate.    A  darkening  indicates  the  pres- 
ence of  unoxidized  sulphur. 

2.  Test  for  Total  Sulphur  (Unoxidized  and  Oxidized). — Place  the  substance 
to  be  examined  (powdered  egg  albumin)  in  a  small  porcelain  crucible,  add  a  suit- 
able amount  of  solid  fusion  mixture  (sodium  carbonate  and  potassium  nitrate 
mixed  hi  the  proportion  2:1)  and  heat  carefully  until  a  colorless  mixture  results. 
(Sodium  peroxide  may  be  used  in  place  of  this  fusion  mixture  if  desired.)    Cool, 
dissolve  the  cake  in  a  little  warm  water  and  filter.    Acidify  the  filtrate  with  hydro- 
chloric acid,  heat  it  to  the  boiling-point  and  add  a  small  amount  of  barium  chlo- 
ride solution.    A  white  precipitate  forms  if  sulphur  is  present.    What  is  this 
precipitate? 

GLOBULINS 

Globulins  are  simple  proteins  especially  predominant  in  the  vege- 
table kingdom.  They  are  closely  related  to  the  albumins  and  in  com- 
mon with  them  give  all  the  ordinary  protein  tests.  Globulins  differ 
from  the  albumins  in  being  insoluble  in  pure  (salt-free)  water.  They 
are,  however,  soluble  in  neutral  solutions  of  salts  of  strong  bases  with 
strong  acids.  Most  globulins  are  precipitated  from  their  solutions  by 
saturation  with  solid  sodium  chloride  or  magnesium  sulphate.  As  a 
class  they  are  much  less  stable  than  the  albumins,  a  fact  shown  by  the 
increasing  difficulty  with  which  a  globulin  dissolves  during  the  course  of 
successive  reprecipitations. 

We  have  used  an  albumin  of  animal  origin  (egg  albumin),  for  all 


io8 


PHYSIOLOGICAL   CHEMISTRY 


the  protein  tests  thus  far,  whereas  the  globulin  to  be  studied  will  be 
prepared  from  a  vegetable  source.  There  being  no  essential  difference 
between  animal  and  vegetable  proteins,  the  vegetable  globulin  we  shall 
study  may  be  taken  as  a  true  type  of  all  globulins,  both  animal  and 
vegetable. 

EXPERIMENTS  ON  GLOBULIN 

Preparation  of  the  Globulin. — Extract  20-30  grams  (a  handful)  of  crushed 
hemp  seed  with  a  5  per  cent  solution  of  sodium  chloride  for  one-half  hour  at 
6o°C.  Filter  while  hot  through  a  paper  moistened  with  5  per  cent  sodium  chloride 
solution.  Place  the  filtrate  in  a  water-bath  at  6o°C.  and  allow  both  to  cool 
spontaneously  and  stand  for  24  hours  hi  order  that  the  globulin  may  crystallize 
slowly  as  the  temperature  of  the  bath  falls.  In  case  the  filtrate  is  cloudy  it  should 
be  warmed  to  6o°C.  in  order  to  produce  a  clear  solution.  The  globulin  is  soluble 


FIG.  37. — EDESTIN. 

in  hot  5  per  cent  sodium  chloride  solution  and  is  thus  extracted  from  the  hemp 
seed,  but  upon  cooling  this  solution  much  of  the  globulin  separates  hi  crystalline 
form.  This  particular  globulin  is  called  edestin.  It  crystallizes  in  several 
different  forms,  chiefly  octahedra  (see  Fig.  37,  above).  (The  crystalline  form 
of  excelsin,  a  protein  obtained  from  the  Brazil  nut,  is  shown  hi  Fig.  38,  p.  109. 
This  vegetable  protein  crystallizes  hi  the  form  of  hexagonal  plates.)  Filter 
off  the  edestin  and  make  the  following  tests  on  the  crystalline  body  and  on  the 
filtrate  which  still  contains  some  of  the  extracted  globulin. 

Tests  on  Crystallized  Edestin. — Microscopical  examination  (see  Fig.  37). 

(2)  Solubility.— Try  the  solubility  in  the  ordinary  solvents  (see  page  22). 
Keep  these  solubilities  in  mind  for  comparison  with  those  of  edestan,  to  be  made 
later  (see  page  114). 

(3)  Millon's  Reaction. 

(4)  Coagulation  Test.— Place  a  small  amount  of  the  globulin  hi  a  test-tube,  add 
a  little  water  and  boil.    Now  add  dilute  hydrochloric  acid  and  note  that  the  pro- 
tein no  longer  dissolves.    It  has  been  coagulated.  „' 


PROTEINS 


ICQ 


(5)  Dissolve  the  remainder  of  the  edestin  in  0.2  per  cent  hydrochloric  acid 
and  preserve  this  acid  solution  for  use  in  the  experiments  on  proteans  (see  page 
114). 

Tests  on  Edestin  Filtrate. — (i)  Influence  of  Protein  Precipitants. — Try  a 
few  protein  precipitants  such  as  nitric  acid,  tannic  acid,  picric  acid,  and  mercuric 
chloride. 

(2)  Biuret  Test. 

(3)  Coagulation  Test.— Boil  some   of  the  filtrate  in  a  test-tube.    What 
happens? 

(4)  Saturation  with  Sodium  Chloride. — Saturate  some  of  the  filtrate  with 
solid  sodium  chloride.    How  does  this  result  differ  from  that  obtained  upon 
saturating  egg  albumin  solution  with  solid  sodium  chloride? 


FIG.  38. — EXCELSIN,  THE  PROTEIN  OF  THE  BRAZIL  NUT. 
(Drawn  from  crystals  furnished  by  Dr.  Thomas  B.  Osborne,  New  Haven,  Conn.) 

(5)  Precipitation  by  Dilution.— Dilute  some  of  the  filtrate  with  10-15  volumes 
of  water.  Why  does  the  globulin  precipitate? 

Glutelins 

It  has  been  repeatedly  shown,  particularly  by  Osborne,  that  after 
extracting  the  seeds  of  cereals  with  water,  neutral  salt  solution,  and 
strong  alcohol,  there  still  remains  a  residue  which  contains  protein 
material  which  may  be  extracted  by  very  dilute  acid  or  alkali.  These 
proteins  which  are  insoluble  in  all  neutral  solvents,  but  readily  soluble 
in  very  dilute  acids  and  alkalis  are  called  glutelins.  The  only  member 
of  the  group  which  has  yet  received  a  name  is  the  glutenin  of  wheat, 
a  protein  which  constitutes  nearly  50  per  cent  of  the  gluten,  the  re- 
mainder being  principally  gliadin.  It  is  not  definitely  known  whether 
glutelins  occur  as  constituents  of  all  seeds. 


110  PHYSIOLOGICAL  CHEMISTRY 

Gluten:  Preparation  and  Tests.1 — To  about  50  grams  of  wheat  flour  in  a 
casserole  or  evaporating  dish,  add  a  little  water  and  mix  thoroughly  until  a  stiff 
dough  results.  Knead  this  dough  thoroughly  and  permit  it  to  stand  for  about  a 
half  hour.  This  is  done  in  order  that  the  maximum  quantity  of  gluten  may  be 
obtained.  Treat  the  dough  with  about  200  c.c.  of  water  and  knead  it  thoroughly. 
Note  the  yellowish  color  of  the  dough  and  the  milky  appearance  of  the  water  due 
to  suspended  starch  granules.  (Place  a  drop  of  the  suspension  on  a  slide,  cover 
with  a  cover  slip,  run  underneath  the  slip  a  drop  of  iodine  solution  and  observe 
the  stained  starch  granules  under  the  microscope.)  Filter  and  apply  a  protein 
color  reaction  (see  page  97)  to  the  filtrate.  It  should  be  positive,  indicating 
that  water-soluble  proteins  were  present  in  the  flour.  Add  fresh  water  to  the 
dough  and  repeat  the  kneading  process.  Continue  this  procedure  with  fresh 
addition  of  water  until  practically  no  starch  granules  are  noted  in  suspension. 
To  a  small  piece  of  the  yellow,  fibrous  gluten  apply  Millon's  Reaction  (page  97). 
This  test  shows  gluten  to  be  protein  material.  Utilize  the  remainder  of  the 
gluten  in  the  preparation  of  gliadin  (page  in). 

Glutenin :  Preparation  and  Tests. — (In  the  preparation  of  gliadin  (page  1 1 1 ) 
it  is  customary  to  remove  this  prolamin  from  the  crude  gluten  by  extracting  with 
70  per  cent  alcohol.  Inasmuch  as  gluten  consists  chiefly  of  gliadin  and  glutenin 
the  portion  of  the  gluten  remaining  after  the  extraction  of  the  alcohol-soluble 
protein  gliadin  may  be  utilized  for  the  preparation  of  glutenin.) 

To  the  finely  divided  residue  from  the  preparation  of  gliadin  (page  in)  hi  a 
flask  or  bottle  add  about  250  c.c.  of  70  per  cent  alcohol.  Allow  to  stand  for  about 
48  hours  with  repeated  shaking  in  order  to  remove  any  remaining  gliadin. 
Crude  glutenin  remains.  To  purify  the  glutenin  treat  it  hi  a  mortar,  with  suffi- 
cient 0.2  per  cent  NaOH  to  dissolve  it,  and  filter  the  liquid  through  a  wet  pleated 
filter.  Neutralize  the  filtrate  carefully,  with  0.2  per  cent  HC1  adding  the  acid 
drop  by  drop  with  thorough  mixing  after  each  addition.  (The  glutenin  is  sol- 
uble in  excess  of  acid.)  Filter  off  the  glutenin  precipitate  and  wash  several 
times  with  70  per  cent  alcohol  and  finally  with  water.  Apply  the  following  tests : 

1.  Solubility  in  water,  salt  solution,  0.2  per  cent  HC1  and  0.5  per  cent  Na2CO3. 

2.  Millon's  Reaction. 

Prolamins  (Alcohol-soluble  Proteins) 

The  term  prolamin  has  been  proposed  by  Osborne  for  the  group  of 
proteins  formerly  termed  "alcohol-soluble  proteins."  The  name  is 
very  appropriate  inasmuch  as  these  proteins  yield,  upon  hydrolysis, 
especially  large  amounts  of  proline  and  ammonia.  The  prolamins  are 
simple  proteins  which  are  insoluble  in  water,  absolute  alcohol  and  other 
neutral  solvents,  but  are  soluble  in  70  to  80  per  cent  alcohol  and  in  dilute 
acids  and  alkalis.  They  occur  widely  distributed,  particularly  in  the 
'  vegetable  kingdom.  The  only  prolamins  yet  described  are  the  zein  of 
maize,  the  hordein  of  barley,  the  gliadin  of  wheat  and  rye,  the  bynin 
of  malt,  and  the  kafirin  of  kafir.  They  yield  relatively  large  amounts 

1  This  experiment  as  well  as  those  on  glutenin  and  gliadin  which  follow  have  been 
adapted  from  directions  given  in  Laboratory  Notes  of  Professor  Gies,  College  of  Physicians 
and  Surgeons,  New  York. 


PROTEINS  III 

of  glutamic  acid  on  hydrolysis  but  no  lysine.  Gliadin  of  wheat  is  an 
exception  to  this  statement  containing  about  0.6  per  cent  lysine.  The 
largest  percentage  of  glutamic  acid  (43.66  per  cent)  ever  obtained  as  a 
decomposition  product  of  a  protein  substance  was  obtained  by  Osborne 
and  Guest  from  the  hydrolysis  of  the  prolamin  gliadin.1  This  yield 
of  glutamic  acid  is  also  the  largest  amount  of  any  single  decomposition 
product  yet  obtained  from  any  protein  except  protamines. 

Gliadin:  Preparation  and  Tests. — Introduce  the  finely  divided  crude  gluten 
as  prepared  on  page  in  into  a  flask  or  bottle,  add  about  250  c.c.  of  70  per  cent 
alcohol2  and  allow  the  mixture  to  stand  24  hours  with  occasional  shaking.  Filter 
(retaining  the  undissolved  portion  for  preparation  of  glutenin,  page  101),  evaporate 
the  filtrate  to  dryness  in  a  porcelain  dish  over  a  water-bath.  Pulverize  the  dry 
material.  Apply  the  following  tests  to  this  gliadin  powder : 

Solubility  and  Protein  Tests.— Test  the  solubility  in  alcohol  (30  per  cent, 
50  per  cent  and  70  per  cent),  water,  0.9  per  cent  NaGl,  0.2  per  cent  HC1  and  0.5 
per  cent  Na2CO3.  Shake  each  test  repeatedly  and  filter.  To  the  filtrate  apply 
Coagulation  test  (page  104)  and  Biuret  test  (page  99). 

Albuminoids    (Scleroproteins) 

The  albuminoids  yield  hydrolytic  products  similar  to  those  obtained 
from  the  other  simple  proteins  already  considered,  thus  indicating  that 
they  possess  essentially  the  same  chemical  structure.  They  differ  from 
all  other  proteins,  whether  simple,  conjugated,  or  derived,  in  that  they 
are  insoluble  in  all  neutral  solvents.  The  albuminoids  include  "the 
principal  organic  constituents  of  the  skeletal  structure  of  animals  as 
well  as  their  external  covering  and  its  appendages."  Some  of  the  princi- 
pal albuminoids  are  keratin,  elastin,  collagen,  reticulin,  spongin,  and 
fibroin.  Gelatin  cannot  be  classed  as  an  albuminoid  although  it  is  a 
transformation  product  of  collagen.  The  various  albuminoids  differ 
from  each  other  in  certain  fundamental  characteristics  which  will  be 
considered  in  detail  under  Epithelial  and  Connective  Tissue  (see 
Chapter  XIX). 

CONJUGATED  PROTEINS 

Conjugated  proteins  consist  of  a  protein  molecule  united  to  some 
other  molecule  or  molecules  otherwise  than  as  a  salt.  We  have  glyco- 
proteins,  nucleo proteins,  hemoglobins  (chromoproteins),  phospho  proteins 
and  lecitho proteins  as  the  five  classes  of  conjugated  proteins. 

Glycoproteins  may  be  considered  as  compounds  of  the  protein  mole- 

1  Osborne  and  Guest:  Jour.  Biol.  Chem.,  9,  425,  1911.    Up  to  this  time  the  yield  of 
41.32  per  cent  obtained  by  Kleinschmitt  from  hordein  was  the  maximum  yield. 

2  Bailey  and  Blish  claim  that  50  per  cent  alcohol  is  more  satisfactory  (Jour.  Biol. 
Chem.,  23,  345,  1915). 


112  PHYSIOLOGICAL   CHEMISTRY 

cule  with  a  substance  or  substances  containing  a  carbohydrate  group 
other  than  a  nucleic  acid.  The  glycoproteins  yield,  upon  decomposition, 
protein  and  carbohydrate  derivatives,  notably  glucosamine,  CH2OH.- 
(CHOH)3.CH(NH2).CHO,  and  galactosamine,  OHCH2.(CHOH)3.CH- 
(NH2).CHO.  The  principal  glycoproteins  are  mucoids,  mucins,  and 
chondro proteins.  By  the  term  mucoid  we  may  in  general  designate 
those  glycoproteins  which  occur  in  tissues,  such  as  tendomucoid  from 
tendinous  tissue  and  osseomucoid  from  bone.  (For  the  preparation  of 
tendomucoid  see  Chapter  XIX.)  The  elementary  composition  of  these 
typical  mucoids  is  as  follows: 

N.  S.  C.  H.          O. 

Tendomucoid1 n-75         2.33        48.76        6.53        30.60 

Osseomucoid2 12.22         2.32        47.43        6.63        31.40 

The  term  mucins  may  be  said  in  general  to  include  those  forms  of  glyco- 
proteins which  occur  in  the  secretions  and  fluids  of  the  body.  (For  the 
preparation  of  salivary  mucin  see  Chapter  III.)  Chondroproteins  are 
so  named  because  chondromucoid,  the  principal  member  of  the  group, 
is  derived  from  cartilage  (chondrigen) .  Amyloid,3  which  appears  patho- 
logically in  the  spleen,  liver,  and  kidneys,  is  also  a  chondroprotein. 

The  phospho proteins  are  considered  to  be  "  compounds  of  the 
protein  molecule  and  some,  as  yet  undefined,  phosphorus-containing 
substances  other  than  a  nucleic  acid  or  lecithin."  The  percentage  of 
phosphorus  in  phosphoproteins  is  very  similar  to  that  in  nucleopro terns, 
but  they  differ  from  this  latter  class  of  proteins  in  that  they  do  not 
yield  any  purine  bases  upon  hydrolytic  cleavage.  Two  of  the  common 
phosphoproteins  are  the  casein  of  milk  and  the  ovovitellin  of  the  egg- 
yolk.  The  phosphorus  in  these,  as  in  all  proteins,  exists  in  phosphoric 
acid  radicals.  For  the  preparation  of  a  typical  phosphoprotein  (casein) 
see-Chapter  XVIII. 

The  hemoglobins  (chromoproteins)  are  compounds  of  the  protein 
molecule  with  hematin  or  some  similar  substance.  The  principal  mem- 
ber of  the  group  is  the  hemoglobin  of  the  blood.  Upon  hydrolytic  cleav- 
age this  hemoglobin  yields  a  protein  termed  globin  and  a  coloring  matter 
termed  hemochromogen.  The  latter  substance  contains  iron  and  upon 
coming  into  contact  with  oxygen  is  oxidized  to  form  hematin.  Hemo- 
cyanin,  another  member  of  the  class  of  hemoglobins,  occurs  in  the  blood 
of  certain  invertebrates,  notably  cephalopods,  gasteropods,  and 

^hittenden  and  Gies:  Jour.  Exp.  Med.,  i,  186,  1896. 
2 Hawk  and  Gies:  Amer.  Jour.  PhysioL,  5,  387,  1901. 

3  Not  to  be  confused  with  the  substance  amyloid  which  may  be  formed  from  cellulose 
(see  p.  48). 


PROTEINS 

Crustacea.  Hemocyanin  generally  contains  either  copper,  manganese, 
or  zinc  in  place  of  the  iron  of  the  hemoglobin  molecule.  For  the  prepa- 
ration of  hemoglobin  in  crystalline  form  see  Chapter  XV. 

The  lecitho proteins  consist  of  a  protein  molecule  joined  to  lecithin. 
They  have  been  comparatively  little  studied  and  may  possibly  be 
mixtures  of  protein  and  lecithin. 

For  consideration  of  nucleo proteins  see  Chapter  VI. 

DERIVED  PROTEINS 

V 

These  substances  are  derivatives  which  are  formed  through  hydro- 
lytic  changes  of  the  original  protein  molecule.  They  may  be  divided 
into  two  groups,  the  primary  protein  derivatives  and  the  secondary 
protein  derivatives.  The  term  secondary  derivatives  is  made  use  of 
in  this  connection  since  the  formation  of  the  primary  derivatives  gener- 
ally precedes  the  formation  of  these  secondary  derivatives.  These 
derived  proteins  are  obtained  from  native  simple  proteins  by  hy- 
drolyses  of  various  kinds,  e.g.,  through  the  action  of  acids,  alkalis, 
heat,  or  enzymes.  The  particular  class  of  derived  protein  desired 
regulates  the  method  of  treatment  to  which  the  native  protein  is 
subjected. 

Primary  Protein  Derivatives 

The  primary  protein  derivatives  are  "apparently  formed  through 
hydrolytic  changes  which  involve  only  slight  alterations  of  the  protein 
molecule."  This  class  includes  proteans,  metaproteins  and  coagulated 
proteins. 

PROTEANS 

Proteans  are  those  insoluble  protein  substances  which  are  produced 
from  proteins  originally  soluble  through  the  incipient  action  of  water, 
enzymes,  or  very  dilute  acids.  It  is  well  known  that  globulins  become 
insoluble  upon  repeated  reprecipitation  and  it  may  possibly  be  found  that 
the  greater  number  of  the  proteans  are  transformed  globulins.  Osborne, 
however,  believes  that  nearly  all  proteins  may  give  rise  to  proteans. 
This  investigator  who  has  so  very  thoroughly  investigated  many  of 
the  vegetable  proteins  claims  that  the  hydrogen  ion  is  the  active  agent 
in  the  transformation.  The  protean  produced  from  the  transformation 
of  edestin  is  called  edestan,  that  produced  irommyosin  is  called  myosan, 
etc.  The  name  protean  was  first  given  to  this  class  of  proteins  by  Os- 
borne in  1900  in  connection  with  his  studies  of  edestin. 

8 


114  PHYSIOLOGICAL  CHEMISTRY 

EXPERIMENTS  ON  PROTEANS 

Preparation  and  Study  of  Edestan. — Prepare  edestin  according  to  the  direc- 
tions given  on  page  108.  Bring  the  edestin  into  solution  in  0.2  per  cent  hydro- 
chloric acid  and  permit  the  acid  solution  to  stand  for  about  one-half  hour.1  Neutral- 
ize with  a  0.5  per  cent  solution  of  sodium  carbonate,  filter  off  the  precipitate  of 
edestan  and  make  the  following  tests: 

1.  Solubility. — Try  the  solubility  in  water,  sodium  chloride,  dilute  acid  and 
alkali.     Note  the  altered  solubility  of  the  edestan  as  compared  with  that  of  edestin 
(see  page  108). 

2.  Millon's  Reaction. 

3.  Coagulation  Test. — Place  a  small  amount  of  the  protean  in  a  test-tube, 
add  a  little  water  and  boil.     Now  add  dilute  hydrochloric  acid  and  note  that 
the  protein  no  longer  dissolves.     It  has  been  coagulated. 

4.  Tests  on  Edestan  Solution. — Dissolve  the  remainder  of  the  edestan  pre- 
cipitate in  0.2  per  cent  hydrochloric  acid  and  make  the  following  tests: 

(a)  Biuret  Test 

(V)  Influence  of  Protein  Precipitant*. — Try  a  few  protein  precipitants  such  as 
picric  acid  and  mercuric  chloride. 

METAPROTEINS 

The  metaproteins  are  formed  from  the  native  simple  proteins 
through  an  action  similar  to  that  by  which  proteans  are  formed.  In 
the  case  of  the  metaproteins,  however,  the  changes  in  the  original  pro- 
tein molecule  are  more  profound.  These  derived  proteins  are  char- 
acterized by  being  soluble  in  very  weak  acids  and  alkalis,  but  insoluble 
in  neutral  fluids.  The  metaproteins  were  formerly  termed  albuminates, 
but  inasmuch  as  the  termination  ate  signifies  a  salt  it  has  always  been 
somewhat  of  a  misnomer. 

Two  of  the  principal  metaproteins  are  the  acid  metaprotein  or  so- 
called  acid  albuminate  and  the  alkali  metaprotein  or  so-called  alkali 
albuminate.  They  differ  from  the  native  simple  proteins  principally  in 
being  insoluble  in  sodium  chloride  solution  and  in  not  being  coagulated 
except  when  suspended  in  neutral  fluids.  Both  forms  of  metaprotein 
are  precipitated  upon  the  approximate  neutralization  of  their  solutions. 
They  are  precipitated  by  saturating  their  solutions  with  ammonium  sul- 
phate, and  by  sodium  chloride  also,  provided  they  are  dissolved  in 
an  acid  solution.  Acid  metaprotein  contains  a  higher  percentage  of 
nitrogen  and  sulphur  than  the  alkali  metaprotein  from  the  same  source, 
since  some  of  the  nitrogen  and  sulphur  of  the  original  protein  is  liberated 
in  the  formation  of  the  latter.  Because  ,of  this  fact,  it  is  impossible 
to  transform  an  alkali  metaprotein  into  an  acid  metaprotein,  while  it 
is  possible  to  reverse  the  process  and  transform  the  acid  metaprotein 
into  the  alkali  modification. 

1  The  edestan  solution  preserved  from  experiment  (5),  p.  109,  may  be  used. 


PROTEINS  115 

EXPERIMENTS  ON  METAPROTEINS 
ACID  METAPROTEIN  (ACID  ALBUMINATE) 

Preparation  and  Study.— Take  25  grams  of  hashed  lean  beef  washed  free 
from  the  major  portion  of  blood  and  inorganic  matter,  and  place  it  in  a  medium- 
sized  beaker  with  100  c.c.  of  0.2  per  cent  HC1.  Place  it  on  a  boiling  water-bath 
for  one-half  hour,  filter,  cool,  and  divide  the  nitrate  into  two  parts.  Neutralize 
the  first  part  with  dilute  KOH  solution,  filter  off  the  precipitate  of  acid  metapro- 
tein  and  make  the  following  tests : 

(1)  Solubility. — Solubility  in  the  ordinary  solvents  (see  page  22). 

(2)  Millon's  Reaction. 

(3)  Coagulation  Test. — Suspend  a  little  of  the  metaprotein  in  water  (neutral 
solution)  and  heat  to  boiling  for  a  few  moments.    Now  add  1-2  drops  of  KOH 
solution  to  the  water  and  see  if  the  metaprotein  is  still  soluble  hi  dilute  alkali. 
What  is  the  result  and  why? 

(4)  Test  for  Unoxidized  Sulphur  (see  page  107).  v 

Subject  the  second  part  of  the  original  solution  to  the  following  tests: 

(5)  Coagulation  Test. — Heat  some  of  the  solution  to  boiling  hi  a  test-tube. 
Does  it  coagulate? 

(6)  Biuret  Test. 

(7)  Influence  of  Protein  Precipitants. — Try  a  few  protein  precipitants  such  as 
picric  acid  and  mercuric  chloride.    How  do  the  results  obtained  compare  with 
those  from  the  experiments  on  egg  albumin?     (See  page  102.) 

ALKALI  METAPROTEIN  (ALKALI  ALBUMINATE) 

Preparation  and  Study. — Carefully  separate  the  white  from  the  yolk  of  a 
hen's  egg  and  place  the  former  in  an  evaporating  dish.  Add  concentrated  potas- 
sium hydroxide  solution,  drop  by  drop,  stirring  continuously.  The  mass  gradu- 
ally thickens  and  finally  assumes  the  consistency  of  jelly.  This  is  solid  alkali 
metaprotein  or  "Lieberkiihn's  jelly."  Do  not  add  an  excess  of  potassium  hydrox- 
ide or  the  jelly  will  dissolve.  Cut  it  into  small  pieces,  place  a  cloth  or  wire  gauze 
over  the  dish,  and  by  means  of  running  water  wash  the  pieces  free  from  adherent 
alkali.  Now  add  a  small  amount  of  water,  which  forms  a  weak  alkaline  solution 
with  the  alkali  within  the  pieces,  and  dissolve  the  jelly  by  gentle  heat.  Cool  the 
solution  and  divide  it  into  two  parts.  Proceed  as  follows  with  the  first  part: 
Neutralize  with  dilute  hydrochloric  acid,  noting  the  odor  of  the  liberated  hydro- 
gen sulphide  as  the  alkali  metaprotein  precipitates.  Filter  off  the  precipitate 
and  test  as  for  acid  metaprotein  (tests  i,  2,  3  and  4),  above,  noting  particularly 
the  sulphur  test.  How  does  this  test  compare  with  that  given  by  the  acid  meta- 
protein? Make  tests  on  the  second  part  of  the  solution  the  same  as  for  acid 
metaprotein  (tests  5,  6  and  7)  above. 

Coagulated  Proteins 

These  derived  proteins  are  produced  from  unaltered  protein  mate- 
rials by  heat,  by  long  standing  under  alcohol,  or  by  the  continuous 
movement  of  their  solutions  such  as  that  produced  by  rapid  stirring  or 
shaking.  In  particular  instances,  such  as  the  formation  of  fibrin  from 


Il6  PHYSIOLOGICAL  CHEMISTRY 

fibrinogen  (see  page  258),  the  coagulation  may  be  produced  by  enzyme 
action.  Ordinary  soluble  proteins  after  having  been  transformed  into 
the  coagulated  modification  are  no  longer  soluble  in  the  ordinary  sol- 
vents. Upon  being  heated  in  the  presence  of  strong  acids  or  alkalis, 
coagulated  proteins  are  converted  into  metaproteins. 

Many  proteins  coagulate  at  an  approximately  fixed  temperature 
under  definite  conditions  (see  pages  104  and  357).  This  characteristic 
may  be  applied  to  separate  different  coagulable  proteins  from  the  same 
solution  by  fractional  coagulation.  The  coagulation  temperature  fre- 
quently may  serve  in  a  measure  to  identify  proteins  in  a  manner  similar 
to  the  melting-point  or  boiling-point  of  many  other  organic  substances. 
The  separation  of  proteins  by  fractional  coagulation  is  thus  analogous 
to  the  separation  of  volatile  substances  by  means  of  fractional  distillation. 
This  method  of  separating  proteins  is  not  a  satisfactory  one,  however, 
inasmuch  as  proteins  in  solution  have  different  effects  upon  one  another 
and  also  because  of  the  fact  that  the  nature  of  the  solvent  causes  a 
variation  in  the  temperature  at  which  a  given  protein  coagulates.  The 
nature  of  the  process  involved  in  the  coagulation  of  proteins  by  heat 
is  not  well  understood,  but  it  is  probable  that  in  addition  to  the  altered 
arrangement  of  the  component  atoms  in  the  molecule,  there  is  a  mild 
hydrolysis  which  is  accompanied  by  the  liberation  of  minute  amounts 
of  hydrogen,  nitrogen,  and  sulphur.  The  presence  of  a  neutral  salt 
or  a  trace  of  mineral  acid  may  facilitate  the  coagulation  of  a  protein 
solution  (see  page  104),  whereas  any  appreciable  amount  of  acid  or 
alkali  will  retard  or  entirely  prevent  such  coagulation. 

It  has  been  shown  that  the  coagulation  of  proteins  by  heat  pro- 
ceeds in  two  stages:1  first,  a  reaction  between  the  protein  and  the  hot 
water  (denaturation) ,  and  second,  an  agglutination  or  separation  of  the 
altered  protein  in  particulate  form.  The  concentration  of  acid,  or 
hydrogen  ion,  in  the  solution  influences  the  coagulation  of  proteins,  such 
that  the  original  protein  is  acted  upon  less  readily  by  hot  water  alone 
than  in  the  presence  of  acid.  The  formation  of  the  coagulum  is  ac- 
companied by  the  disappearance  of  the  free  acid  from  the  solution, 
indicating  the  formation  of  a  protein  salt.  A  disturbance  of  the  equi- 
librium between  the  hydrolyzed  and  unhydrolyzed  portions  of  the  pro- 
tein salt,  due  to  the  greater  rapidity  with  which  the  unhydrolyzed 
portion  is  precipitated,  results  in  the  gradual  removal  of  both  pro- 
tein and  acid  from  the  solution.  This  has  been  offered  as  an  explana-* 
tion  of  the  decreasing  acidity. 

According  to  Chick  and  Martin,  the  addition  of  neutral  salts  to  the 
acid  solution  of  the  salt-free  protein  to  be  coagulated  results  in  a  decreased 

1  Chick  and  Martin-  Journal  of  Physiology,  43   i,  1911. 


PROTEINS 


117 


rate  of  coagulation.  This  is  due  in  part  to  the  decrease  in  the  concen- 
tration of  the  free  acid,  which  results  from  the  disturbance  of  the  equilib- 
rium between  the  protein  and  acid  and  also  in  part  to  the  direct  influence 
which  the  salts  exert  upon  the  protein.  The  presence  of  neutral  salts 
may  under  certain  circumstances  facilitate  the  coagulation  of  proteins 
by  heat. 

The  temperature  at  which  egg-white  is  coagulated  causes  a  difference 
in  the  appearance  of  the  coagulum.1  Coagulated  egg-white  which  has 
been  immersed  in  water  at  a  low  temperature  and  then  gradually  heated 
to  the  coagulating  temperature  is  more  translucent  and  has  a  bluish 
color,  whereas  egg-white  which  has  been  immersed  in  water  heated  to  a 
temperature  above  the  coagulating  temperature  is  creamy  white  in 
color.  They  also  possess  different  digestibilities. 

x-  s 

EXPERIMENTS   ON   COAGULATED*  PROTEIN 

Ordinary  coagulated  egg-white  may  be  used  in  the  following  tests : 

1.  Solubility. — Try  the  solubility  of  small  pieces  of  coagulated  protein  in 
each  of  the  ordinary  solvents  (see  page  22). 

2.  Millon's  Reaction. 

3.  Xanthoproteic  Reaction. — Partly  dissolve  a  medium-sized  piece  of  the 
protein  in  concentrated  nitric  acid.    Cool  the  solution  and  add  an  excess  of 
ammonium  hydroxide.    Both  the  protein  solution  and  the  undissolved  protein 
will  be  colored  orange. 

4.  Biuret  Test. — Partly  dissolve  a  medium-sized  piece  of  the  protein  in  con- 
centrated potassium  hydroxide  solution.    If  the  proper  dilution  of  copper  sul- 
phate solution  is  now  added  the  white  coagulated  protein,  as  well  as  the  protein 
solution,  will  assume  the  characteristic  purplish-violet  color. 

5.  Glyoxylic  Acid  Reaction  (Hopkins-Cole). — Conduct  this  test  according  to 
the  modification  given  on  page  98. 

Secondary  Protein  Derivatives 

These  derivatives  result  from  a  more  profound  cleavage  of  the  protein 
molecule  than  that  which  occurs  in  the  formation  of  the  primary  deriva- 
tives. The  class  included  proteases,  peptones,  and  peptides. 

PROTEOSES  AND  PEPTONES 

Proteoses  are  intermediate  products  in  the  digestion  of  proteins  by 
proteoly tic  enzymes,  as  well  as  in  the  decomposition  of  proteins  by  hy- 
drolysis and  the  putrefaction  of  proteins  through  the  action  of  bacteria. 
Proteoses  are  called  albumoses  by  some  writers,  but  it  seems  more  logical 
to  reserve  the  term  albumose  for  the  proteose  of  albumin. 

Peptones  are  formed  after  the  proteoses  and  it  has  been  customary  to 

1  Frank:  Journal  of  Biological  Chemistry,  9,  463,  1911. 


Il8  PHYSIOLOGICAL  CHEMISTRY 

consider  them  as  the  last  product  of  the  processes  before  mentioned 
which  still  possess  true  protein  characteristics.  In  other  words,  it  has 
been  considered  that  the  protein  nature  of  the  end-products  of  the 
cleavage  of  the  protein  molecule  ceased  with  the  peptones,  and  that  the 
simpler  bodies  formed  from  peptones  were  substances  of  a  different 
nature  (see  page  64).  However,  as  the  end-products  have  been  more 
carefully  studied,  it  has  been  found  to  be  no  easy  matter  to  designate 
the  exact  character  of  a  peptone  or  to  indicate  the  exact  point  at 
which  the  peptone  characteristic  ends  and  the  peptide  characteristic 
begins.  The  situation  regarding  the  proteoses,  peptones  and  peptides 
is  at  present  a  most  unsatisfactory  one  because  of  the  unsettled  state 
of  our  knowledge  regarding  them.  The  exact  differences  between 
certain  members  of  the  peptone  and  peptide  groups  remain  to  be  more 
accurately  established.  ^  It  has  been  quite  well  established  that  the 
peptones  are  peptides  or  mixtures  of  peptides,  but  the  term  peptide  is 
used  at  present  to  designate  only  those  possessing  a  definite  structure. 
There  are  several  proteoses  (protoproteose,  heteroproteose  and 
deuteroproteose),  and  at  least  two  peptones  (amphopeptone  and  anti- 
peptone),  which  result  from  proteolysis.  The  differentiation  of  the 
various  proteoses  and  peptones  at  present  in  use  is  rather  unsatisfactory. 
These  compounds  are  classified  according  to  their  varying  solubilities, 
especially  in  ammonium  sulphate  solutions  of  different  strengths.  The 
exact  differences  in  composition  between  the  various  members  of  the 
group  remain  to  be  more  accurately  established.  Because  of  the 
difficulty  attending  the  separation  of  these  bodies,  pure  proteose  and 
peptone  are  not  easy  to  procure.  -The  so-called  peptones  sold  com- 
mercially contain  a  large  amount  of  proteose.  As  a  class  the  proteoses 
and  peptones  are  very  soluble,  diffusible  bodies  which  are  non-coagu- 
lable  by  heat.  Peptones  differ  from  proteoses  in  being  more  diffusible, 
non-precipitable  by  (NH4)2S04,  and  by  their  failure  to  give  any  reaction 
with  potassium  ferrocyanide  and  acetic  acid,  potassio-mer curie  iodide 
and  HC1,  picric  acid,  and  trichlor acetic  acid.  Peptones  may  be  pre- 
cipitated by  phosphotungstic  acid,  phosphomolybdic  acid,  absolute 
alcohol  and  tannic  acid,  but  an  excess  of  the  precipitant  may  dissolve 
the  precipitate.  The  so-called  primary  proteoses  are  precipitated  by 
HN03  and  are  the  only  members  of  the  proteose-peptone  group  which 
are  so  precipitated. 

Some  of  the  more  general  characteristics  of  the  proteose-peptone  group  may 
be  noted  by  making  the  following  simple  tests  on  a  proteose-peptone  powder : 

(1)  Solubility. — Solubility  in  hot  and  cold  water  and  sodium  chloride  solution. 

(2)  Millon's  Reaction. 

Dissolve  a  little  of  the  powder  in  water  and  test  the  solution  as  follows : 


PROTEINS 

(1)  Precipitation  by  Picric  Acid. — To  5  c.c.  of  proteose-peptone  solution  in  a 
test-tube  add  picric  acid  until  a  permanent  precipitate  forms.    The  precipitate 
disappears  on  heating  and  returns  on  cooling. 

(2)  Precipitation  by  a  Mineral  Acid. — Try  the  precipitation  by  nitric  acid. 

(3)  Coagulation  Test. — Heat  a  little  proteose-peptone  solution  to  boiling. 
Does  it  coagulate  like  the  other  simple  proteins  studied? 

SEPARATION  OF  PROTEOSES  AND  PEPTONES1 

Place  50  c.c.  of  proteose-peptone  solution  in  an  evaporating  dish  or  casserole, 
and  half-saturate  it  with  ammonium  sulphate  solution,  which  may  be  accom- 
plished by  adding  an  equal  volume  of  saturated  ammonium  sulphate  solution. 
At  this  point  note  the  appearance  of  a  precipitate  of  the  primary  proteoses 
(protoproteose  and  heteroproteose).  Now  heat  the  half-saturated  solution  and 
its  suspended  precipitate  to  boiling  and  saturate  the  solution  with  solid  am- 
monium sulphate.  At  full  saturation  the  secondary  proteoses  (deuteroproteoses) 
are  precipitated.  The  peptones  remain  in  solution.  ^ 

Proceed  as  follows  with  the  precipitate  of  proteoses:  Collect  the  sticky 
precipitate  on  a  rubber-tipped  stirring  rod  or  remove  it  by  means  of  a  watch 
glass  to  a  small  evaporating  dish  and  dissolve  it  hi  a  little  water.  To  remove  the 
ammonium  sulphate,  which  adhered  to  the  precipitate  and  is  now  hi  solution, 
add  barium  carbonate,  boil,  and  filter  off  the  precipitate  of  barium  sulphate. 
Concentrate  the  proteose  solution  to  a  small  volume2  and  make  the  follow- 
ing tests : 

(1)  BiuretTest. 

(2)  Precipitation  by  Nitric  Acid. — What  .would  a  precipitate  at  this  point 
indicate? 

(3)  Precipitation   by   Trichloracetic   Acid.— This   precipitate  dissolves  on 
heating  and  returns  on  cooling. 

(4)  Precipitation  by  Picric  Acid. — This  precipitate  also  disappears  on  heat- 
ing and  returns  on  cooling. 

(5)  Precipitation  by  Potassio -mercuric  Iodide  and  Hydrochloric  Acid. 

(6)  Coagulation  Test. — Boil  a  little  hi  a  test-tube.    Does  it  coagulate? 

(7)  Acetic  Acid  and  Potassium  Ferrocyanide  Test. 

The  solution  containing  the  peptones  should  be  cooled  and  filtered,  and  the 
ammonium  sulphate  hi  solution  removed  by  boiling  with  barium  carbonate  as 
described  above.  After  filtering  off  the  barium  sulphate  precipitate,  concentrate 
the  peptone  filtrate  to  a  small  volume  and  repeat  the  tests  as  given  under  the 
proteose  solution,  above.  Also  try  the  precipitation  by  phosphotungstic  acid 
and  by  tannic  acid.  In  the  biuret  test  the  solution  should  be  made  very  strongly 
alkaline  with  solid  potassium  hydroxide. 

PEPTIDES 

The  pep  tides  are  "definitely  characterized  combinations  of  two  or 
more  amino  acids,  the  carboxyl  (COOH)  group  of  one  being  united 

1  The  separation  of  proteoses  and  peptones  by  means  of  fractional  precipitation  with 
ammonium  sulphate  does  not  possess  the  significance  it  was  once  supposed  to  possess  inas- 
much as  the  boundary  between  these  substances  undfeptidesiz  not  well  defined  (see  p.  117). 

8  If  the  proteoses  are  desired  in  powder  form,  this  concentrated  proteose  solution  may- 
now  be  precipitated  by  alcohol,  and  this  precipitate,  after  being  washed  with  absolute 
alcohol  and  with  ether,  may  be  dried  and  powdered. 


I2O 


PHYSIOLOGICAL   CHEMISTRY 


with  the  amino  (NH2)  group  of  the  other  with  the  elimination  of  a  mole- 
cule of  water."  These  pep  tides  are  more  fully  discussed  on  pages  69 
and  118. 

REVIEW    OF    PROTEINS 

In  order  to  facilitate  the  student's  review  of  the  proteins,  the  prepara- 
tion of  a  chart  similar  to  the  model  given  is  recommended.  The  signs 
+  and  —  may  be  conveniently  used  to  indicate  positive  and  negative 
reactions. 

MODEL  CHART  FOR  REVIEW  PURPOSES 


f  ' 
Protein 

Solubility 

Protein  Color  Test 

Precipitation  Tests 

Salting- 
out 
Tests 

Diffusion 
Coagulation  by  Heat 

I 

I 

0 

0 

M 

6 

6 
o 

to 

6 

0 

3 

w 

0 

i 

Mineral  Acid  (HNOi) 

Metallic  Salt  (HgCh) 

Alcohol 

•s-d 
11 

I! 
r 

Potassio-mercur  ic 
Iodide  +  HC1 

is 
9 

0 

*n 
.y 

Trichloracetic  Acid 

»OS«(»HN) 

0 
55 

Albumin 

i 

Globulin 

Nucleoprotein 

Phosphoprotein 

1 

E 

| 

Glycoprotein 

— 

— 





— 

" 



-*• 

! 

Acid  metaprotein 





— 



— 

Alkali  metaprotein 

Proteose 

| 

Peptone 

i 

Coagulated  protein 

! 

! 

I 

"UNKNOWN"  MIXTURES  AND  SOLUTIONS  OF  PROTEINS 

At  this  point  the  student's  knowledge  of  the  characteristics  of  the 
various  proteins  studied  will  be  tested  by  requiring  him  to  examine  sev- 
eral "unknown"  protein  mixtures  or  solutions  and  make  full  report 
upon  the  same.  The  scheme  given  on  page  121  may  be  used  in  this 
examination. 


PROTEINS 


121 


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CHAPTER  VI 
NUCLEIC  ACIDS  AND  NTJCLEOPROTEINS1 

The  Nucleoproteins. — The  nucleoproteins  occur  widely  distributed 
in  the  animal  and  plant  kingdoms,  being  found  in  nearly  all  cells  and 
particularly  in  the  nuclei  of  cells.  They  are  found  in  especially  large 
amounts  in  glandular  tissues  such  as  those  of  the  thymus,  pancreas  and 
spleen.  The  nucleoproteins  are  combinations  of  protein  with  a  phos- 
phorus-containing substance  known  as  nucleic  acid.  As  different  nu- 
cleic acids  exist  and  are  found  in  combination  with  different  proteins, 
a  variety  of  nucleoproteins  exist.  The  protein  combined  with  the 
nucleic  acid  is  in  certain  cases  a  histone,  the  conjugated  protein  in 
this  case  being  called  a  nucleohistone. 

The  nucleoproteins  give  the  ordinary  protein  color  reactions.  They 
are  acidic  in  character  and  insoluble  in  water.  They  are  readily  soluble 
in  weak  alkali  but  are  precipitated  from  such  solution  on  the  addi- 
tion of  acetic  acid  in  excess  of  which  they  dissolve  with  more  or  less 
difficulty  although  readily  soluble  in  excess  of  dilute  hydrochloric  acid. 
We  distinguish  them  from  mucins,  which  are  likewise  precipitated  by 
acetic  acid  through  the  fact  that  the  latter  give  no  tests  for  phosphorus 
on  decomposition. 

The  nucleoproteins  are  very  complex  and  unstable  substances  and 
are  probably  in  many  cases  to  be  considered  as  mixtures  of  protein  and 
nucleic  acid  rather  than  as  definite  compounds.  Under  the  ac- 
tion of  the  gastric  juice  or  of  weak  acid  nucleoproteins  lose  a  portion  of 
their  protein  content  and  are  transformed  into  a  rather  ill-defined  class 
of  substances  known  as  nucleins  which  still  possess  some  protein  in 
combination  with  the  nucleic  acid  molecule.  In  most  cases  the  decom- 
position does  not  proceed  further  in  gastric  digestion.  Through  the 
action  of  the  pancreatic  juice,  however,  the  remainder  of  the  protein  is 
split  off  and  the  nucleic  acid  set  free.  The  decomposition  of  nucleo- 
protein  may  be  diagrammatically  expressed  thus,  although  the  course 
of  decomposition  is  probably  not  quite  so  simple  as  indicated. 

1  For  review  of  the  literature  on  nucleic  acids  and  nucleuses  see  Monograph  on  "Nucleic 
Acids"  by  Walter  Jones,  New  York,  1920,  Longmans  Green  &  Co. 


NUCLEIC  ACIDS   AND   NUCLEOPROTEINS  123 

NUCLEOPROTEIN 
I 

(gastric  digestion) 


Protein  Nuclein 

i 
(pancreatic  digestion) 


Protein  Nucleic  Acid 


The  Nucleic  Acids. — The  nucleic  acids  of  the  animal  body  occur 
mainly  in  combination  with  protein  material  in  the  so-called  nucleo- 
proteins  of  which  they  form  the  characteristic  radicals  (see  page  123). 
The  amount  and  character  of  the  protein  with  which  the  nucleic  acid 
molecule  is  combined  varies  and  the  acid  may^m  certain  cases  be  found 
in  cells  in  a  free  form.  Naturally  those  tissues  are  richest  in  nucleic 
acid  which  contain  the  largest  amount  of  nuclear  material  and  of 
nucleoprotein.  Such  are  the  glandular  tissues  of  the  body  as  the  thy- 
mus,  spleen,  pancreas,  liver,  etc.  The  heads  of  the  spermatozoa  con- 
sist almost  entirely  of  nucleic  acid  in  combination  with  protamine. 

The  nucleic  acids  are  a  distinct  class  of  substances,  characterized 
by  their  decomposition  products.  They  are  strongly  acid  in  reaction 
and  contain  considerable  phosphorus.  'They  may  be  divided  into  two 
main  groups,  the  animal  and  the  plant  nucleic  acids.  The  two  classes 
differ  in  certain  respects  but  all  of  the  true  animal  nucleic  acids  appear 
to  be  practically  identical  in  composition.  Animal  nucleic  acid  is  most 
readily  prepared  from  the  thymus  while  plant  nucleic  acid  is  most 
readily  obtained  from  yeast. 

The  nucleic  acids  are  difficultly  soluble  in  cold  water,  more  readily 
in  hot  water,  insoluble  in  alcohol,  but  readily  soluble  in  weak  alkali 
with  the  formation  of  the  alkali  salt.  If  pure  they  do  not  give  the  pro- 
tein color  reactions.  They  are  optically  active.  They  are  precipitated 
from  their  alkaline  solutions  by  HC1,  but  only  the  plant  nucleic  acid  is 
precipitated  by  acetic  acid.  In  weak  acid  solution  they  are  precipi- 
tated by  protein  the  combination  being  considered  a  "nuclein."  They 
form  insoluble  salts  with  alkaline  earth  and  heavy  metals.  The  sodium 
salt  of  animal  nucleic  acid  in  4  per  cent  solution  is  liquid  while  warm  but 
solidifies  to  a  gelatinous  mass  on  cooling.  Plant  nucleic  acid  does  not 
do  this. 

The  nucleic  acids  on  hydrolysis  yield  phosphoric  acid,  purine  and 
pyrimidine  bases,  and  a  carbohydrate  or  carbohydrate  derivative.  The 
composition  varies  slightly  with  the  type  of  nucleic  acid.  Plant  nucleic 
acids  contain  a  pentose  group  (d-ribose)  while  animal  nucleic  acids  con- 


I24 


PHYSIOLOGICAL   CHEMISTRY 


tain  a  hexose  group.  Both  types  contain  the  purine  bases,  guanine  and 
adenine  and  the  pyrimidine  base  cytosine.  Plant  nucleic  acid  contains 
also  the  pyrimidine  base  uracil,  which  in  the  animal  nucleic  acid  is  sub- 
stituted by  the  base  thymine.  The  nucleic  acids  are  not,  however, 
simple  substances  whose  molecules  contain  a  single  phosphoric  acid  or 
carbohydrate  group.  They  are  apparently  combinations  of  several 
radicals  known  as  nucleotides  each  of  which  contains  one  carbohydrate 
group  combined  with  a  single  base  and  a  single  phosphoric  acid 
molecule.  Thus  the  following  structural  formula  has  been  sug- 
gested for  yeast  nucleic  acid  by  Jones  and  Read1  indicating  that  it 
contains  four  nucleotide  radicals  linked  through  the  carbohydrate 
groups.  Levene2  does  not  consider  this  linkage  through  carbohydrate 
as  established.  All  agree  that  the  compound  is  a  tetranucleotide. 


HO 


\ 


HO 


Adenine  group 


O 


HO 


\ 


/ 


HO 


Uracil  group 


O 


HO 


\ 


0 = P  -  0-  C5H6O-  C4H4N3O 

Cytosine  group 

HO 

0 
HO 

0 = P-  0-  C5H702-  C5H4N60 

/  Guanine  group 

HO 

Yeast  nucleic  acid  (tetranucleotide) 

The  cleavage  of  the  nucleic  acid  molecule  into  its  corresponding 
nucleotides  is  brought  about  during  digestion  by  enzymes  present  in  the 
intestinal  juice  and  intestinal  mucosa.  Enzymes  of  similar  origin 
act  further  on  the  nucleotides  thus  formed  and  split  off  the  phosphoric 
acid  radicals  together  with  carbohydrate-base  compounds  which  are 
called  nucleosides.  The  decomposition  prior  to  absorption  does  not 
probably  proceed  further  than  to  the  formation  of  nucleotides  and 


1  Jones  and  Read:  Jour.  BioL  Chem.,  31,  in,  1917. 

2  Levene:  Jour.  BioL  Chem.,  31,  591,  1917. 


NUCLEIC  ACIDS   AND   NUCLEOPROTEINS  125 

nucleosides.  Many  tissues  however  contain  enzymes  capable  of 
completing  the  decomposition  with  liberation  of  the  carbohydrate  and 
basic  radicals.  The  purine  bases  may  also  be  deaminized  while  still 
in  combination  as  nucleosides  and  further  hydrolysis  would  then  lead 
to  the  direct  liberation  of  the  oxypurines  instead  of  their  precursors, 
the  amino-purines. 

Jones1  has  suggested  a  method  by  which  the  course  of  the  decom- 
position of  the  nucleic  acid  molecule  can  be  followed.  By  this  means 
it  is  readily  shown  that  phosphoric  acid  is  liberated  at  very  different 
rates  from  the  different  nucleotides. 

The  following  outline  will  indicate  the  course  of  decomposition  of  a 
nucleic  acid  and  the  enzymes  involved  in  the  process. 

DECOMPOSITION  OF  NUCLEIC  ACID 
NUCLEIC  ACID         v 

(nucleicacidase  of  intestinal  mucosa  and  juice) 

Purine  Nucleotides  Pyrimidine  Nucleotides 

(nucleotidase  of  intestinal  (tissue  nucleases) 

mucosa  and  juice) 

F"  I  Sugar 

Phosphoric  Acid        Purine  Nucleosides  Phosphoric  Acid 

I  Pyrimidine  Bases 

Cytosine  and  Thymine 
(nucleosidase  of  tissues)  or  Uracil 

Sugar  Purine  Bases 

(pentose  or  hexose)  Adenine 

Guanine 

With  regard  to  the  fate  of  the  various  radicals  of  the  nucleic  acids 
in  the  body  after  absorption  little  is  definitely  known.  The  phosphoric 
acid  may  of  course  be  built  up  into  phosphorus-containing  cell  con- 
stituents such  as  nucleoproteins,  phosphoproteins  or  phosphatides,  or 
be  eliminated  as. phosphate  in  the  urine.  The  carbohydrate  portion 
may  undergo  the  usual  transformations  of  intermediary  carbohydrate 
metabolism.  The  nucleosides  appear  to  be  ordinarily  absorbed  un- 
changed from  the  intestine  and  may  be  to  a  certain  extent  directly  re- 
synthesized  in  the  animal  body  to  nucleoprotein.  The  excess  over  body 
requirement  must,  however,  be  decomposed,  although  a  certain  portion 
may  possibly  be  stored  up  in  the  individual  cells  or  in  certain  organs. 
Enzymes  capable  of  decomposing  nucleic  acids  are  found  in  most  of  the 
cells  of  the  body. 

The  Purine  Bases. — As  has  been  indicated  the  basic  substances 
present  in  nucleic  acid  belong  to  two  classes  the  purine  and  pyrimidine 

.  l  Jones:  Presidential  address  before  the  Society  of  Biological  Chemists,  Boston,  Dec. 
27,  1915. 


126 


PHYSIOLOGICAL   CHEMISTRY 


bases.  The  purine  bases  set  free  on  the  decomposition  of  nucleic  acid 
are  adenine  and  guanine  belonging  to  the  class  of  amino  purines.  The 
fate  of  the  amino  purines  in  the  animal  body  is  of  considerable  interest. 
It  has  been  shown  that  certain  tissues  contain  enzymes  which  transform 
these  amino  purines  first  to  corresponding  oxypurines  known  as  hypo- 
xanthine  and  xanthine  and  finally  to  uric  acid.  It  is  probable  that  differ- 
ent enzymes  enter  into  the  various  steps  of  these  transformations  lead- 
ing to  the  formation  of  uric  acid.  Still  another  enzyme  carries  the  oxi- 
dation further  with  the  formation  of  the  compound  allantoin.  This 
enzyme  is  known  as  uricase.  The  purine-  enzymes  are  widely  dis- 
tributed in  tissues.  The  transformations  brought  about  are  indicated 
in  the  following  diagrams. 


N=CNH2 

i 

HC    C— NH 
\ 


CH 


HN— CO 


+H2O-»NH,+    HC     C— NH 

\ 


Adenase 


N— C— N 

Adenine 
6-amino  purine 


CH 


N— C— N 

Hypoxanthine 
6-oxypurine 


+0 


Hypoxanthine 
oxidase 


HN— CO 


HN— CO 

I       I 
OC     C— NH 


H2N-C     C— NH 
\ 
CH  +H2O-»NH3+ 

<y  Guanase 

N— C— N  HN— C— N 

Guanine  Xanthine 

2-amino-6-oxypurine  2 -6-dioxy  purine 


CH 


+0 


Xanthine 
oxidase 


NH5 


CO      CO— NH          0+H2O 

\  Uricase 

CO 


NH— CH— NH 

Allantoin 


HN— CO 

I       I 
OC     C— NH 

\ 
CO 

HN— C— NH 

Uric  acid 
2-6-8-trioxypurine 


NUCLEIC  ACIDS  AND   NUCLEOPROTEINS  127 

All  of  the  physiologically  important  purine  bodies  are  precipitated 
by  ammoniacal  silver  nitrate  solution  in  the  cold  and  by  copper  sul- 
phate and  sodium  bisulphite  in  boiling  solutions.  Some  of  them  are 
readily  identified  by  their  crystalline  forms  or  the  crystalline  forms  of 
certain  of  their  salts.  Uric  acid  differs  from  the  other  purines  in  being 
insoluble  in  dilute  sulphuric  acid.  The  purine  bodies  may  be  distin- 
guished to  a  certain  extent  also  by  the  reactions  which  they  give  when 
their  solutions  are  evaporated  with  nitric  acid  and  the  residue  treated 
with  ammonia.  Uric  acid  gives  the  characteristic  formation  of  the 
purple  murexide  (ammonium  purpurate)  .  Potassium  hydroxide  changes 
this  to  a  bluish-violet  color  which  disappears  on  heating.  Xanthine 
and  guanine  form  yellow  compounds  with  nitric  acid  which  turn 
purple  or  violet  on  treating  with  potassium  hydroxide.  The  color  in 
this  case  is  not  lost  by  heating.  Adenine  and  hypoxanthine  do  not 
give  a  color  reaction  with  nitric  acid.  j.  .~ 

The  Pyrimidine  Bases.  —  The  pyrimidine  bases  entering  into  the 
composition  of  nucleic  acid  are  thymine,  cytosine  and  uracil.  Cytosine 
is  found  in  both  types  of  nucleic  acid,  while  thymine  is  found  only 
in  animal  nucleic  acid  and  uracil  only  in  plant  nucleic  acid.  They 
possess  the  following  formulas. 

NH—  C=  O  NH—  C=  O  N=C—  NH2 


CH  0=C        C—  CH3         O^=C        CH 

I         II  I         II  I          II 

NH—  CH  NH—  CH  NH—  CH 

Uracil  .  Thymine  Cytosine 

2-6-dioxypyrimidine  5  -methyl-  6-amino- 

2-6-dioxypyrimidine  2-oxypyrimidine 

With  regard  to  the  fate  of  pyrimidine  bases  in  metabolism  very 
little  is  known.  When  the  bases  as  such  are  fed  they  reappear  un- 
changed in  the  urine.1  If  nucleic  acid  is  fed  this  does  not  occur  which 
indicates  that  the  pyrimidine  bases  may  undergo  certain  alterations 
in  the  animal  body  while  still  existing  in  combination. 

EXPERIMENTS 

i.  Preparation  of  Nucleoprotein  from  Yeast.2  —  Place  two  small  cakes  of  ordi- 
nary compressed  yeast  in  a  mortar.  Sprinkle  a  small  horn-spoonful  of  sand  over 
the  yeast,  add  5  c.c.  of  ether  and  10  c.c.  of  water  and  thoroughly  triturate  the 
mixture,  grinding  vigorously.  The  ether  kills  the  yeast,  in  which  condition  the 
comminution  of  the  cells  with  sand  is  more  thoroughly  effected.  Occasionally 
during  the  trituration  process  add  i  or  2  c.c.  of  water  until  the  mixture  is 
comparatively  fluid.  The  whole  process  of  maceration  can  be  completed  in  five 

1  Mendel  and  Myers:  Am.  J.  PhysioL,  26,  77,  1910. 

*  All  experiments  on  nucleoprotein  of  yeast  have  been  taken  from  Laboratory  Notes  of 
Professor  W.  J.  Gies,  of  College  of  Physicians  and  Surgeons,  New  York. 


128  PHYSIOLOGICAL   CHEMISTRY 

minutes.  Pour  the  thick  liquid  into  a  bottle  aiding  the  transfer  with  enough 
0.4  per  cent  NaOH  to  make  a  final  volume  of  about  i25.c.c.  The  alkali  extracts 
the  nucleoprotein  along  with  the  water-soluble  proteins  of  the  yeast.  Add  a  little 
toluene  and  allow  to  stand  with  frequent  shaking  for  12-24  hours.  Filter  through 
a  wet,  fluted  filter.  While  thoroughly  stirring  add  i  drop  at  a  time  of  10  per  cent 
HC1  cautiously  continuing  the  addition  as  long  as  the  milkiness  of  the  mixture  can 
be  increased.  Continue  until  the  protein  completely  separates  and  the  liquid  is 
practically  clear.  Note  that  the  solution  is  now  acid  in  reaction.  Excess  of  acid 
causes  resolution.  Filter  on  a  wet,  fluted  filter.  Retain  the  precipitate  on  the 
filter  for  nucleoprotein  tests. 

2.  Tests  on  Nucleoprotein. — Try  the  following  tests  on  the  nucleoprotein 
prepared  as  above. 

(a)  Try  the  xanthoproteic  and  Millon's  tests. 

(b)  Test  the  solubility  in  water,  10  per  cent  NaCl,  10  per  cent  HC1,  dilute 
KOH,  and  alcohol. 

(c)  Test    for  organically    combined  phosphorus    by    one    of    the  following 
methods. 

Tests  for  Phosphorus  in  Organic  Matter. — i.  Fusion  Test. — To  a  small 
amount  of  the  substance  in  a  crucible  add  about  five  times  its  bulk  of  fusion  mix- 
ture (2  parts  of  sodium  carbonate  to  i  of  potassium  nitrate).  Heat  carefully  until 
the  resulting  mixture  is  colorless.  Cool,  dissolve  the  mass  in  a  little  warm  water, 
acidify  with  nitric  acid,  heat  to  about  6s°C.  and  add  a  few  cubic  centimeters  of 
molybdate  solution.  In  the  presence  of  phosphorus  a  yellow  precipitate  of  am- 
monium phosphomolybdate  is  formed. 

Instead  of  acidifying  with  nitric  acid,  the  aqueous  solution  may  be  approxi- 
mately neutralized  with  hydrochloric  acid,  a  few  cubic  centimeters  of  magnesia 
mixture  added  and  then  excess  of  ammonium  hydroxide  solution.  A  white  pre- 
cipitate of  magnesium  ammonium  phosphate  is  formed. 

2.  Moist  Ashing  Procedure. — Treat  a  small  amount  of  the  substance  in  a 
large  test-tube  with  about  i  c.c.  of  concentrated  sulphuric  acid.    Then  add  drop  by 
drop  an  equal  volume  of  concentrated  nitric  acid,  and  warm  gently  until  a  clear 
solution  is  obtained.    A  few  more  drops  of  nitric  acid  may  be  added  if  necessary. 
This  treatment  with  sulphuric  and  nitric  acids  must  be  carried  out  with  the 
greatest  caution  particularly  when  fatty  substances  are  present;  otherwise  an 
explosive  reaction  may  take  place.    Dilute  the  acid  solution  with  a  little  water, 
make  slightly  alkaline  with  ammonia  and  then  acid  with  nitric  acid.    Add 
molybdate  solution  and  warm.    A  yellow  precipitate  is  formed. 

(d)  Dissolve  a  little  of  the  precipitate  in  very  dilute  KOH  and  then  make 
slightly  acid  with  acetic  acid. 

(e)  Mix  a  small  portion  of  the  nucleoprotein  with  10  c.c.  of  alcohol.    Filter 
and  wash  free  from  HC1  with  more  alcohol.     (Freedom  from  HC1  is  indicated  by 
absence  of  AgNO3-chloride  reaction  hi  the  filtrate.)    Wash  free  from  alcohol 
with  a  little  water.    Transfer  small  particles  of  the  precipitate  to  moistened  red 
and  blue  litmus  paper  on  a  microscopic  slide.    What  is  the  reaction  of  nucleo- 
protein thus  freed  from  adherent  acid? 

3.  To  Show  the  Presence  of  Purine  Base  Radicals  hi  Nucleoprotein.— The 
nucleic  acid  portion  of  the  protein  molecule  contains  phosphoric  acid,  carbohy- 
drate, and  purin  base  radicals  (see  page  125).    Hence  on  the  complete  acid  hydro- 
lysis of  nucleoprotein  material  these  substances  will  be  liberated  as  well  as  the 
decomposition  products  of  the  protein  part  of  the  molecule.    To  showv  their  pres- 


NUCLEIC   ACIDS   AND    NUCLEOPROTEINS  129 

ence  proceed  as  follows:  Transfer  the  precipitate  of  nucleoprotein  remaining 
from  the  previous  experiment  to  a  small  flask  and  add  25-50  c.c.  of  5  per  cent 
H2SO4.  Boil  for  an  hour  or  more  to  decompose.  Maintain  the  original  volume 
by  adding  water.  The  solution  becomes  brown  due  to  formation  of  melanin- 
like  substances.  The  purine  bases  are  set  free.  Retain  one-fourth  of  the  solu- 
tion for  the  next  experiment.  Transfer  the  remainder  to  a  casserole  and  add 
ammonia  with  thorough  mixing,  a  little  at  a  time,  until  the  fluid  is  nearly  neutral. 
Then  make  slightly  alkaline  with  dilute  ammonia  and  filter  if  not  clear.  Transfer 
to  a  beaker  and  add  about  10  c.c.  of  5  per  cent  ammoniacal  silver  nitrate  solution. 
Purine  bases  if  present  will  yield  a  brown  flocculent  precipitate  of  their  silver 
compounds.  If  a  precipitate  does  not  appear  immediately,  examine  the  solution 
after  it  has  been  allowed  to  stand  for  some  time  undisturbed. 

4.  To  show  the  Presence  of  Protein,  Carbohydrate,  and  Phosphoric  Acid 
Radicals  in  Nucleoprotein. — Filter  the  greater  portion  of  the  acid  liquid  which  was 
reserved  from  the  preceding  experiment.    Apply  the  following  tests  to  portions  of 
it:     (a)  The  biuret  test,     (b)  The  xanthoproteic  test,     (c)  Molisch  test     (d) 
Fehling's  test,     (e)  Test  for  phosphate. 

5.  Preparation  of  Thymus  Nucleoprotein. — About  100  grams  of  fresh  thymus 
gland  (lymphatic  glands  may  also  be  used)  freed  as  nearly  as  possible  from  adherent 
fat  are  run  through  a  meat  chopper.     To  this  material  in  a  flask  add  300  c.c.  of  0.9 
per  cent  NaCl  and  allow  to  stand  24-48  hours  in  the  cold.     A  little  chloroform  and 
toluene  should  be  added  as  preservatives,  and  the  mixture  shaken  occasionally  dur- 
ing this  period.     Filter.     A  milk  white  liquid  is  obtained.     Precipitate  the  nucleo- 
protein from  solution  by  the  careful  addition  of  dilute  acetic  acid.    Excess  of  the 
acid  should  be  avoided.     Ordinarily  acetic  acid  to  make  a  i  per  cent  solution  is 
sufficient.     Filter  off  the  precipitate.     Wash  with  alcohol  and  then  with  ether  and 
dry. 

6.  Experiments  on  Thymus  Nucleoprotein. — Repeat  the  experiments  given 
under  Yeast  Nucleoprotein  (page  128). 

7.  Preparation  of  Yeast  Nucleic  Acid. — Dilute  50  c.c.  of  i  per  cent  NaOH 
with  250  c.c.  of  water  in  a  casserole  and  add  to  this  solution  100  grams  of  com- 
pressed yeast  cut  in  small  pieces.    Heat  on  the  water-bath  for  half  an  hour  with 
occasional  stirring.    Remove  from  the  bath  and  filter  at  once  through  a  folded 
filter.    To  the  cooled  filtrate  add  acetic  acid  until  faintly  acid  to  litmus.    Filter 
again.    Evaporate  the  solution  to  100  c.c.  or  less  and  filter  if  necessary.    Allow 
to  cool  to  4O°C.  or  below,  then  pour  with  vigorous  stirring  into  200  c.c.  of  95  per 
cent  alcohol  containing  2  c.c.  of  concentrated  HC1.    Allow  to  settle  and  wash  the 
precipitate  by  decantation  hi  a  tall  vessel,  twice  with  95  per  cent  alcohol  and 
twice  with  ether.    Transfer  to  a  filter  paper.    Allow  to  drain  and  dry  at  room 
temperature. 

8.  Tests  on  Nucleic  Acid  from  Yeast.1 — i.  Test  the  solubility  of  nucleic  acid 
in  cold  and  hot  water,  in  alcohol,  and  hi  dilute  acid  and  alkali.    To  the  solution  in 
alkali  add  dilute  HC1  drop  by  drop  until  the  solution  is  acid,  then  add  excess  of 
concentrated  HC1. 

Does  nucleic  acid  coagulate  on  boiling?    Does  the  solution  hi  hot  water 
gelatinize  on  cooling? 

2.  Try  xanthoproteic  reaction  and  biuret  test. 

3.  Dissolve  a  little  nucleic  acid  hi  water  with  the  aid  of  heat.    Test  the  re- 

1A  satisfactory  preparation  of  yeast  nucleic  acid  may  be  obtained  from  Merck  and  Co. 
9 


130  PHYSIOLOGICAL   CHEMISTRY 

action  of  different  portions  of  the  solution  with  litmus,  alizarin,  and  Congo  red 
solution. 

4.  Boil  a  small  portion  of  the  nucleic  acid  with  about  10  c.c.  of  10  per  cent 
sulphuric  acid  for  one  to  two  minutes.  Divide  into  three  portions. 

(a)  To  one  portion  apply  carbohydrate  tests,  e.g.,  the  a-naphthol  (Molisch) 
reaction  and  Bial's  test.    What  do  these  indicate? 

(b)  To  a  second  portion  apply  a  test  for  purine  bases.    Add  an  excess  of 
ammonia  and  then  a  little  silver  nitrate  solution. 

(c)  To  the  third  portion  apply  test  for  phosphate,  adding  ammonia  in  slight 
excess,  then  making  acid  with  nitric  acid,  adding  molybdic  solution  and  wanning. 

9.  Preparation  of  Thymus  Nucleic  Acid.1 — "To  a  boiling  mixture  of  200  c.c.  of 
water,  10  grams  of  sodium  acetate  and  3.3  grams  of  NaOH,  is  added  in  small  suc- 
cessive portions  100  grams  of  trimmed  and  finely  ground  thymus  gland.  The  tissue 
usually  dissolves  completely  forming  a  pale  brown  liquid,  but  any  resistant  portions 
are  either  removed  or  gotten  into  solution  by  heating  for  a  short  time  over  a  small 
flame.  The  vessel  containing  the  products  is  now  immersed  in  a  briskly  boiling 
water-bath  where  it  is  allowed  to  remain  with  occasional  stirring  for  two  hours, 
when  the  product  is  diluted  with  one-third  its  volume  of  water  and  made  faintly 
but  distinctly  acid  to  litmus  with  50  per  cent  acetic  acid.  The  amount  of  acid 
required  is  about  10  c.c.  but  the  final  additions  must  be  made  with  care  because  the 
fluid  will  not  filter  unless  the  proper  condition  of  acidity  is  reached.  Any  difficulty 
met  at  this  point  may  be  easily  overcome  by  the  alternate  addition  of  acetic  acid  and 
sodium  hydroxide  and  testing  a  small  portion  of  the  material  after  each  addition  on 
a  small  flat  filter  that  has  been  heated  with  boiling  water.  When  the  acidity  has 
finally  been  obtained  which  is  favorable  to  rapid  nitration,  the  material  is  heated  to 
vigorous  boiling  and  filtered  with  a  hot  water  funnel.  Under  proper  conditions  the 
filtration  proceeds  with  considerable  rapidity  and  continuously  leaves  a  green  slime 
on  the  filter  and  gives  a  pale  yellow  filtrate  which  gelatinizes  upon  cooling.  The 
filtrate  and  washings  are  evaporated  on  a  water-bath  to  about  75  c.c.  and  while  warm 
the  concentrated  solution  is  poured  slowly  into  100  c.c.  of  95  per  cent  alcohol.  On 
standing  over  night  the  precipitated  sodium  nucleate  settles  sharply  to  a  spongy 
white  mass  from  which  the  bulk  of  brown  alcoholic  fluid  can  be  sharply  decanted 
and  the  remainder  pressed  out  with  a  spatula  leaving  the  material  in  one  cohesive 
mass.  The  substance  is  washed  by  decantation  in  turn  with  80  per  cent  and  95  per 
cent  alcohol  and,  after  pressing  out  the  last  wash  fluid  as  far  as  possible  is  transferred 
to  a  flask  with  30  c.c.  of  hot  water  and  heated  on  a  water-bath.  In  half  an  hour  or 
less,  insoluble  phosphates  will  collect  leaving  a  perfectly  transparent  interstitial 
fluid  which  is  treated  with  i  c.c.  of  20  per  cent  NaOH  to  lower  the  viscosity  and 
filtered  with  a  hot  water  funnel.  The  perfectly  transparent  yellow  filtrate  is  acidi- 
fied with  acetic  acid  and  poured  into  70  c.c.  of  95  per  cent  alcohol  when  sodium 
nucleate  will  be  precipitated  which  can  be  washed  by  decantation  as  before  with 
alcohol  of  increasing  strength  and  ground  in  a  mortar  with  absolute  alcohol  until 
it  has  crumbled  to  a  fine  white  powder.  If  necessary  the  absolute  alcohol  may  be 
decanted  and  renewed  once  or  twice  but  not  oftener  because  the  nucleate  emulsifies 
with  alcohol  after  the  last  traces  of  acetic  acid  and  sodium  acetate  have  been  washed 
away.  The  material  is  finally  washed  on  a  filter  with  absolute  alcohol  and  allowed 
to  dry  in  a  sulphuric  acid  desiccator.  The  yield  of  nucleic  acid  is  about  3.3  grams 
from  100  grams  of  gland.  The  product  is  a  fine  white  non-hygroscopic  powder 

1  From  Monograph  on  "Nucleic  Acids"  by  Walter  Jones:  Longmans,  Green  &  Co. 


NUCLEIC  ACIDS   AND   NUCLEOPKOTEINS  131 

that  can  scarcely  be  improved  by  any  method  of  purification.  It  is  a  soluble 
sodium  salt  of  thymus  nucleic  acid  but  is  generally  referred  to  simply  as  thymus 
nucleic  acid.  Very  similar  or  identical  substances  may  be  prepared  by  the  same 
procedure  from  other  animal  tissues,  rich  in  cell  nuclei  such  as  the  pancreas  and 
spleen." 

10.  Tests  on  Thymus  Nucleic  Acid.— 1-4.  Repeat  the  experiments  as  given 
under  yeast  nucleic  acid,  page  129.     5.  Make  a  4  per  cent  solution  of  thymus  nucleic 
acid  in  hot  water  (0.4  gram  to  10  c.c.).     Allow  to  cool.     What  happens?     Divide 
into  two  portions.     To  one  add  a  little  NaOH  solution;  to  the  other  add  acetic  acid. 
Then  neutralize  carefully  in  each  case. 

Both  acetic  acid  and  NaOH  decrease  the  viscosity  of  the  nucleate  solution.  It 
may  be  changed  back  and  forth  from  the  gelatinous  to  the  fluid  condition  by  the 
alternate  addition  of  acid  and  alkali. 

11.  Tests   on   Purine   Bases   and   Derivatives. — (a)    Xanthine. — i.   Silver 
Nitrate  Reaction. — Dissolve  a  little  xanthine  in  ammonia  and  add  silver  nitrate 
solution.    Examine  a  little  of  the  precipitate  microscopically.     (See  page  369.) 

2.  Copper  Sulphate  Reaction. — Dissolve  a  little  of  the  substance  in  dilute 
alkali,  make  faintly  acid  with  acetic  acid.    Heat  to  boiling.    Add  i  c.c.  10 
per  cent  CuSO4  and  then  a  few  drops  at  a  time  of  sodium  bisulphite  (saturated 
solution)  until  the  precipitate  becomes  yellowish.    All  of  the  purines  give  this 
reaction. 

3.  Nitric  Acid  Test. — Place  a  small  amount  of  the  substance  in  a  small 
evaporating  dish,  add  a  few  drops  of  concentrated  nitric  acid,  and  evaporate  to 
dryness  very  carefully  on  a  water-bath.    The  yellow  residue  upon  moistening 
with  caustic  potash  becomes  red  hi  color  and  upon  further  heating  assumes 
a  purplish-red  hue.    Now  add  a  few  drops  of  water  and  warm.    A  yellow 
solution  results  which  yields  a  red  residue  upon  evaporation.    Compare  with 
similar   reaction  on    other  purine  bases  and  uric  acid.      (See  Murexide  test. 
Chapter  XXEH.) 

4.  Weidel's  Reaction. — Bring  a  small  amount  of  the  substance  into  solution  in 
bromine  water.    Evaporate  to  dryness  on  a  water-bath.    Remove  the  stopper 
from  an  ammonia  bottle  and  by  blowing  across  the  mouth  of  the  bottle  direct  the 
fumes  of  ammonia  so  that  they  come  into  contact  with  the  dry  residue.    Under 
these  conditions  the  presence  of  xanthine  is  shown  by  the  residue  assuming  a  red 
color.    A  somewhat  brighter  color  may  be  obtained  by  using  a  trace  of  nitric  acid 
with  the  bromine  water.    By  the  use  of  this  modification,  however,  we  may  get  a 
positive  reaction  with  bodies  other  than  xanthine. 

(b)  Hypoxanthine. — i.  Repeat  Experiments  i  and  3  under  Xanthine.    Ex- 
amine the  crystals  of  hypoxanthine  silver  nitrate  under  the  microscope.     (See 
page  369.) 

2.  Dissolve  a  little  of  the  substance  in  a  very  small  amount  of  hot  6  per  cent 
nitric  acid  and  allow  to  cool.  Characteristic  whetstone  crystals  of  hypoxanthine 
nitrate  should  be  formed.  Examine  under  the  microscope.  (See  Fig.  40,  page 

1350 

(c)  Adenine. — i.  Warm  a  few  crystals  of  adenine  hi  a  test-tube  with  a  little 
water.    They  should  become  cloudy  at  53 °C. 

2.  Dissolve  a  little  adenine  in  hot  water  and  add  a  few  drops  of  picric  acid. 
Examine  the  pale  yellow  crystals  under  the  microscope.    The  picrate  crystal- 
lizes as  needle  clusters. 

3.  Repeat  Experiment  3  under  Xanthine. 


132  PHYSIOLOGICAL   CHEMISTRY 

(d)  Guanine. — i.  Dissolve  a  little  substance  in  20-25  times  its  weight  of 
boiling  5  per  cent  alcohol.    Allow  to  cool  and  examine  crystals  microscopically. 

2.  For  other  tests  oh  uric  acid  see  Chapter  XXIII  on  Urine. 

3.  Dissolve  a  little  guanine  in  20-25  times  its  weight  of  boiling  5  per  cent 
hydrochloric  acid.    Allow  to   cool  and   examine   crystals  under  microscope. 
(See  Fig.  39,  page  134.) 

4.  Perform  Experiment  3  under  Xanthine. 

(e)  Uric  Acid. — i.  On  a  small  amount  of  uric  acid  try  the  test  as  given  under 
Xanthine  number  3.    This  test  on  uric  acid  is  called  the  Murexide  test. 

12.  Isolation  of  Guanine  and  Adenine  from  Nucleic  Acid  (Method  of  Wal- 
ter Jones).1 — The  amino  purines  may  be  isolated  from  yeast  or  thymus  nucleic  acid 
or  from  glandular  tissue  (such  as  the  pancreas)  after  hydrolysis  of  the  material  with 
sulphuric  acid. 

In  the  case  of  yeast  nucleic  acid,  heat  10  grams  of  the  substance  with  50  c.c.  of 
to  per  cent  sulphuric  acid  on  a  boiling  water-bath  for  about  two  hours,  replacing 
any  water  lost,  or  using  a  condenser  tube.  To  the  hot  solution  add  concentrated 
ammonia  slowly  until  approximately  neutral.  Then  add  enough  excess  of  ammonia 
to  make  about  a  2  per  cent  solution.  Filter  off  the  precipitate  of  guanine  and  wash 
it  with  i  per  cent  ammonia.  Dissolve  in  as  small  an  amount  of  20  per  cent  sul- 
phuric acid  as  possible,  add  a  little  animal  charcoal  and  boil  Filter,  heat  to  boiling 
and  precipitate  with  excess  of  ammonia.  Filter,  dry  the  precipitate  at  4o°C.  and 
dissolve  it  in  about  20  parts  of  boiling  5  per  cent  hydrochloric  acid.  As  the  solu- 
tion cools  guanine  chloride  separates  out  as  needle-shaped  crystals.  Filter  off, 
wash  with  very  dilute  hydrochloric  acid  and  dry  in  the  air  (do  not  put  in  desiccator). 
Perform  the  nitric  acid  test  on  the  product. 

Combine  the  ammoniacal  nitrates  obtained  in  the  isolation  and  purification  of 
guanine.  Filter  if  necessary.  The  ammonia  may  then  be  boiled  off  and  an  excess 
of  picric  acid  added  in  which  case  a  yellow  precipitate  of  adenine  picrate  is  produced 
which  is  filtered  off  and  dried.  It  is  better,  however,  to  neutralize  the  ammonia  of 
the  combined  filtrates  and  make  faintly  acid  with  sulphuric  acid.  Then  precipitate 
the  adenine  as  its  copper  compound  (see  directions  under  experiment  on  Demonstra- 
tion of  Nucleases  B)  decomposing  this  with  hydrogen  sulphide  and  evaporating  the 
filtrate  from  the  copper  sulphide  to  dryness  on  the  water-bath.  Dissolve  the  residue 
in  hot  5  per  cent  sulphuric  acid  and  allow  to  crystallize  out.  If  necessary  dissolve 
in  hot  water  decolorize  with  a  little  charcoal  and  allow  to  crystallize  out  again. 
The  compound  has  the  formula  (CsHsNs^.H^SO^E^O.  Apply  the  picric  acid 
and  nitric  acid  tests  as  given  under  adenine  (page  131). 

13.  The    Pyrimidine    Derivatives. — The    pyrimidine   derivatives, 
cytosine,  thymine,  and  uracil,  are  separated  from  nucleic  acid  with 
some  difficulty.     The  following  test  may  be  made  on  a  solution  of 
cytosine  or  uracil.     Thymine  does  not  give  the  test. 

Wheeler- Johnson  Reaction  for  Uracil  and  Cytosine. — To  about  5  c.c.  of  the 
solution  under  examination  add  bromine  water  until  the  color  is  permanent. 
Avoid  the  addition  of  a  large  excess  as  this  will  interfere  with  the  test.  In 
case  the  solution  contains  only  small  quantities  of  cytosine  or  uracil  it  is  advis- 
able to  remove  any  excess  of  bromine  by  passing  a  stream  of  ah-  through  the 

1See  Walter  Jones:  Monograph  on  "Nucleic  Acids,"  1914,  Longmans,  Green  &  Co. 


NUCLEIC   ACIDS   AND    NUCLEOPROTEINS  133 

solution.    Now  add  an  excess  of  an  aqueous  solution  of  barium  hydroxide 
and  note  the  appearance  of  a  purple  color. 

Very  dilute  solutions  do  not  give  the  test.  Under  these  conditions 
the  solution  should  be  evaporated  to  dryness,  the  residue  dissolved  in  a 
little  bromine  water  and  the  excess  of  bromine  removed.  Then  upon 
adding  an  excess  of  barium  hydroxide  a  decided  bluish-pink  or  lavender 
color  will  appear  in  the  presence  of  as  small  an  amount  as  o.ooi  gram  of 
uracil. 

In  testing  solutions  for  cytosine  it  is  preferable  to  warm  or  boil  the 
solution  with  bromine  water,  and  after  cooling  the  solution  to  apply 
the  test  as  suggested  above,  being  careful  to  have  a  slight  excess  of 
bromine  present  before  adding  barium  hydroxide. 

14.  Demonstration  of  Nucleases  and  Purinases  in  Tissues.1— All 
glandular  tissues  contain  nucleic  acids  and  enzymes  capable  of  their 
hydrolysis  as  well  as  the  transformation  of  liberated  purine  bodies. 
By  allowing  autolysis  (self-digestion)  to  take  place  in  such  a  tissue  and 
studying  the  products  formed  it  is  possible  to  determine  what  enzymes 
were  present  in  the  tissue  under  examination.  Typical  results  may  be 
obtained  by  using  ox  and  pig  spleens,  which  differ  in  the  purine  enzymes 
which  they  contain.  The  two  experiments  should  be  run  in  parallel. 

A.  Preparation  of  the  Material  for  Digestion.— Run  thie  gland  once  or  twice 
through  a  meat  chopper.    Introduce  about  650  grams  into  a  two  liter  bottle,  fill 
about  three-quarters  full  of  water,  add  20  c.c.  of  chloroform,  and  allow  to  remain 
at  room  temperature  for  12-36  hours  with  occasional  agitation.    Strain  through 
linen  and  replace  the  turbid  extract  hi  the  bottle  with  10  c.c.  of  chloroform.    This 
solution  contains  the  enzymes  and  nucleic  acid  of  the  tissue.     (Reserve  50  c.c. 
of  one  of  the  extracts  for  the  experiment  on  phosphonuclease  (E),  which  should 
also  be  started  at  this  time.)    The  bottle  is  tightly  closed  and  allowed  to  remain 
in  the  thermostat  4-5  days. 

B.  Separation  of  Purine  Derivatives  from  Other  Substances.— Introduce 
the  products  into  a  saucepan  or  large  evaporating  dish,  heat  to  brisk  boiling, 
make  faintly  alkaline  with  caustic  soda,  boil  a  few  minutes,  make  faintly  acid  with 
acetic  acid,  boil  vigorously  and  filter  hot.     (If  desired  one-half  of  the  filtrate  may 
be  treated  with  100  c.c.  of  20  per  cent  sulphuric  acid  per  liter  and  boiled  for  one 
hour,  keeping  at  constant  volume.    At  the  end  of  the  hydrolysis  the  sulphuric  acid 
is  nearly  neutralized  with  caustic  soda  and  the  purine  bases  of  the  solution 
determined  as  in  the  other  half  of  the  filtrate.    This  will  give  information  as  to 
the  presence  of  deaminases  acting  upon  the  amino  purines  remaining  in  combina- 
tion.)   To  the  boiling  filtrate  add  100  c.c.  of  10  per  cent  copper  sulphate  and  small 
successive  portions  (2-5  c.c.)  of  sodium  bisulphite  (commercial  saturated  solution) 
until  the  precipitate  takes  on  a  decided  yellow  color  due  to  precipitation  of  cuprous 
oxide.    Filter,  wash  the  precipitate  with  boiling  water,  pierce  the  filter  and  wash 
the  precipitate  into  a  flask.    Add  i  per  cent  sodium  sulphide  solution  to  decom- 

lFrom  Monograph  on  "Nucleic  Acids"  and  Laboratory  Notes  in  Physiological  Chem- 
istry by  Professor  Walter  Jones  of  Johns  Hopkins  University,  with  additions. 


134 


PHYSIOLOGICAL  CHEMISTRY 


pose  the  copper  compound  continuing  the  addition  until  the  precipitate  becomes 
uniformly  black  and  then  in  small  successive  portions,  testing  a  drop  of  the  prod- 
uct after  each  addition  by  bringing  it  into  contact  with  a  drop  of  lead  acetate 
on  a  filter  paper.  To  the  boiling  fluid  add  acetic  acid  (in  the  case  of  the  extract 
of  pig's  spleen  and  other  solutions  containing  guanine  the  acetic  acid  should  be 
replaced  by  dilute  sulphuric)  until  the  insoluble  copper  sulphide  collects  and  filter 
the  hot  fluid  as  quickly  as  possible. 

C.  Treatment  of  the  Filtrate  from  Pig's  Spleen. — When  the  filtrate  from  the 
copper  sulphide  is  cold  make  strongly  alkaline  with  ammonia  and  precipitate  the 
purine  compounds  with  a  slight  excess  of  ammoniacal  silver  nitrate.  Filter,  wash 
thoroughly  with  cold  water.  Pierce  the  paper,  wash  the  precipitate  into  a  flask 
with  boiling  water  and  decompose  the  silver  precipitate  with  hydrochloric  acid. 
When  enough  acid  has  been  added  the  silver  chloride  will  settle  as  a  heavy  case- 
ous precipitate  leaving  clear  interstitial  fluid.  Filter  and  heat  the  filtrate  to 
boiling.  Treat  with  an  excess  of  ammonia  (enough  to  make  about  1-2  per  cent). 


FIG.  39. — GUANINE  CHLORIDE. 
(Reproduced  from  crystals  furnished  by  Professor  Walter  Jones.) 

Allow  to  cool  and  filter  off  the  guanine  which  precipitates.  Wash  the  guanine 
with  i  per  cent  ammonia  and  then  suspend  it  in  a  little  hot  water  and  add  a  few 
drops  of  20  per  cent  sulphuric  acid  to  dissolve  it.  At  the  boiling  point  add  a  little 
animal  charcoal,  boil  and  filter.  Make  strongly  alkaline  with  ammonia.  Snow 
white  guanine  is  precipitated.  Dissolve  the  precipitate  in  20  volumes  of  boiling 

5  per  cent  hydrochloric  acid.    Upon  cooling  beautiful  needle-shaped  crystals  of 
guanine  chloride  separate.     (See  Fig.  39.) 

Evaporate  the  filtrate  from  the  guanine  to  dryness  on  the  water-bath  to  expel 
ammonia.  Mpisten  with  hydrochloric  acid  and  again  evaporate.  Treat  the 
residue  with  warm  water.  Does  it  dissolve  almost  completely  indicating  the 
absence  of  xanthine  and  uric  acid?  Test  a  drop  of  the  solution  with  picric  acid. 
If  no  precipitate  is  obtained  adenine  is  absent.  Evaporate  to  dryness,  moisten 
with  alcohol  and  again  evaporate.  Dissolve  the  residue  in  about  30  parts  of  hot 

6  per  cent  nitric  acid.    On  cooling,  characteristic  whetstone  crystals  of  hypo- 
xanthine  nitrate  form.     (See  Fig.  40,  page  135.)    The  xanthine  nitric  acid 
color  test  should  be  practically  negative  on  this  product. 


TSTUCLEIC  ACIDS   AND   NUCLEOPROTEINS  135 

What  does  the  finding  of  guanine  and  hypoxanthine  but  not  adenine  or  xan- 
thine  indicate  as  to  the  type  of  purine  deaminase  present  in  the  pig's  spleen? 

D.  Treatment  of  Filtrate  from  Ox  Spleen. — The  filtrate  from  the  copper  sul- 
phide should  be  evaporated  to  dryness  on  the  water-bath.  Extract  with  cold 
water.  Test  a  part  of  this  aqueous  solution  with  picric  acid.  A  lack  of  precipi- 
tate indicates  the  absence  of  adenine.  To  another  portion  add  ammonia  (a 
lack  of  precipitate  indicates  the  absence  of  guanine),  and  then  a  little  ammo- 
niacal  silver  nitrate  solution  (lack  of  appreciable  precipitate  indicates  absence  of 
purines  of  any  kind  in  more  than  traces).  Dissolve  hah*  of  the  residue,  which 
should  consist  mainly  of  uric  acid  and  xanthine,  in  as  few  drops  of  concentrated 
sulphuric  acid  as  possible  and  dilute  with  4  volumes  of  water.  Stir  until  the 
uric  acid  begins  to  separate  and  then  let  stand  for  about  three  hours.  The  uric 
acid  is  completely  precipitated.  Apply  the  murexide  test.  To  the  remainder 
of  the  xanthine-uric  acid  residue  add  a  little  4  per  cent  potassium  hydroxide  solu- 
tion. Warm  and  add  an  equal  volume  of  30  per  cent  nitric  acid.  Allow  to  cool. 


FIG.  40. — HYPOXANTHINE  CHLORIDE. l 
(Reproduced  from  crystals  furnished  by  Professor  Walter  Jones.) 

Xanthine  nitrate  separates  out  in  a  granular  form,  showing  characteristic  crystals 
under  the  microscope.  Apply  the  nitric  acid  test. 

What  does  the  presence  of  uric  acid  and  xanthine  and  the  absence  of  guanine 
and  adenine  indicate  as  to  the  purine  enzymes  of  ox  spleen? 

E.  Demonstration  of  Nucleotidase  (Phosphonuclease). — In  this  experiment 
use  the  50  c.c.  portion  of  enzyme  solution  retained  from  Experiment  A  preceding. 
Prepare  a  2  per  cent  solution  of  yeast  nucleic  acid  aiding  the  solution  by  the  slow 
addition  of  KOH  solution  until  the  reaction,  as  indicated  by  a  few  drops  of  litmus 
added,  is  neutral.  Prepare  a  series  of  three  large  test-tubes  as  follows :  In  No.  i 
place  10  c.c.  of  enzyme  solution  and  5  c.c.  of  nucleic  acid.  In  No.  2  place  10  c.c. 
of  enzyme  solution  and  5  c.c.  of  water.  In  No.  3  place  10  c.c.  of  enzyme  solution, 
boiled  and  5  c.c.  of  nucleic  acid.  To  each  tube  add  2-3  c.c.  each  of  CHCU  and 
toluene  as  preservatives.  Place  the  tubes  at  37°C.  for  24  hours.  Add  i  c.c.  of 
litmus  solution  to  each  tube  and  note  whether  any  changes  in  reaction  have  taken 

1  Hypoxanthine  nitrate  crystallizes  in  similar  form. 


136  PHYSIOLOGICAL  CHEMISTRY 

place.  Put  the  tubes  in  boiling  water  for  a  few  minutes  to  coagulate  proteins. 
Then  add  5  c.c.  of  5  per  cent  HC1  and  let  stand  for  an  hour.  This  precipitates 
any  unaltered  nucleic  acid  which  may  be  present.  Filter  and  take  an  aliquot 
portion  of  each  filtrate  (15  c.c.).  Add  magnesia  mixture  and  a  few  cubic  centi- 
meters of  strong  ammonia.  Let  stand  over  night.  Any  phosphoric  acid  present 
will  be  precipitated  as  magnesium  ammonium  phosphate.  Observe  the  relative 
amounts  of  phosphate  in  each  case.  Has  any  phosphate  been  set  free  from  the 
nucleic  acid  added?  From  the  nucleic  acid  of  the  gland  extract? 

15.  Experiments  on  Uncase  (Uricolytic  Enzyme). — A.  Preparation  of  Extract 
Containing  Uricase. — Extract  about  50  grams  of  pulped  kidney  tissue  of  the  ox 
with  200  c.c.  of  toluene  or  chloroform  water  at  38°C.  for  24  hours,  with  occasional 
shaking.  Filter  and  use  the  filtrate  in  the  following  experiment. 

B.  Demonstration  of  Uricase. — Add  about  o.i  gram  of  uric  acid  to  10  c.c. 
of  water  and  bring  the  uric  acid  into  solution  by  the  addition  of  the  minimal  quan- 
tity of  KOH.  To  5  c.c.  of  this  uric  acid  solution  in  a  test-tube  add  50  c.c.  of  the 
uricolytic  enzyme  extract  prepared  as  described  above.  Prepare  a  second  tube 
containing  a  like  amount  of  the  uric  acid  solution  but  boil  the  extract  before 
it  is  introduced.  Place  the  two  tubes  at  38°C.  for  two  days.  The  vessels  should 
be  open  to  the  air  and  the  contents  stirred  occasionally,  or  much  better,  a  con- 
tinuous current  of  air  which  has  gone  through  a  chloroform  wash  bottle  is  passed 
through  the  mixture.  Make  both  mixtures  faintly  acid  with  acetic  acid  and 
boil.  Filter  and  take  an  aliquot  of  each  filtrate.  Evaporate  to  low  volume,  make 
faintly  alkaline  with  ammonia  and  filter.  Add  a  few  cubic  centimeters  of 
ammoniacal  silver  nitrate  solution.  Any  uric  acid  will  be  precipitated  as  silver 
urate.  The  control  should  give  a  heavy  precipitate  while  the  test  should  show 
no  precipitate  or  one  much  lighter  than  the  control,  due  to  uric  acid  destruction  hi 
the  latter  case. 

If  it  is  desired  to  separate  out  the  pure  uric  acid  the  silver -purine  precipitate 
may  then  be  filtered  off.  It  is  washed  with  water  and  transferred  to  a  beaker  with 
the  aid  of  a  little  water.  To  the  mixture  add  a  few  cubic  centimeters  of  hydrogen 
sulphide  solution  and  a  few  drops  of  HC1  and  allow  to  stand  over  night.  The  uric 
acid  should  separate  out  hi  crystalline  form  and  should  be  found  in  less  amount 
in  the  test  than  hi  the  control  experiment.  The  uric  acid  may  also  be  titrated 
with  permanganate  as  in  the  Folin-Shaffer  method  for  uric  acid  in  urine.  (See 
Chapter  XXVII  on  Quantitative  Analysis  of  Urine.)  This  will  enable  us  to 
determine  exactly  how  much  of  the  uric  acid  was  destroyed  through  the  action 
of  the  enzyme  extract. 


CHAPTER   VII 
GASTRIC  DIGESTION 

GASTRIC  digestion  takes  place  in  the  stomach  and  is  promoted  by 
the  gastric  juice,  which  is  secreted  by  the  glands  of  the  stomach  mucosa. 
These  glands  are  of  two  kinds,  fundus  glands  and  pyloric  glands  which 
are  situated,  as  their  names  imply,  in  the  regions  of  the  fundus  and 
pylorus.  The  principal  foods  acted  upon  in  gastric  digestion  are  the 
proteins  which  are  so  changed  by  its  processes  as  to  become  better  pre- 
pared for  further  digestion  in  the  intestine  and  for  their  final  absorption. 

From  reliable  experiments  made  upon  lower  animals  and  man  it  is 
evident  that  the  gastric  juice  is  secreted  as  the  result  of  stimuli  of  two 
forms,  i.e. ,  psychical  stimuli  and  chemical  stimuii .  The  psychical  form  of 
stimuli  may  be  produced  by  the  sight,  thought,  or  taste  of  food,  and  the 
chemical  stimuli  may  be  produced  by  certain  substances,  such  as  water, 
milk,  the  extractives  of  meat,  etc.,  when  coming  in  contact  with  the 
stomach  mucosa.  The  stimulatory  power  of  water  has  been  very 
strikingly  demonstrated.1  y^he  claim  that  the  drinking  of  water  with 
meals  is  harmful  because  such  a  procedure  causes  a  dilution  of  the  gastric 
juice,  has  no  basis  in  fact.  The  drinking  of  water  with  meals  by  normal 
individuals  has  been  found  to  be  accompanied  by  a  more  economical 
utilization  of  the  ingested  proteins,  fats  and  carbohydrates.  Various 
other  desirable  and  no  undesirable  features  have  been  demonstrated 
as  accompanying  or  following  such  a  dietary  procedure.2  No  experi- 
mental evidence  has  been  submitted  which  can  justly  be  interpreted  as 
showing  any  harmful  influence  to  accompany  or  follow  the  drinking, 
by  normal  persons,  of  large  quantities  of  water  at  meal  time./ 

The  volume  of  gastric  juice  secreted  during  any  given  period  of 
digestion  varies  with  the  quantity  and  kind  of  the  food.  These  con- 
clusions were  deduced  principally  from  a  series  of  so-called  delusive 
feeding  experiments.  A  dog  was  prepared  with  two  esophageal  open- 
ings and  a  gastric  fistula.  When  thus  prepared  and  fed  foods  of  various 

1  Foster  and  Lambert:  Journ.  Exper.  Med.,  10,  820,  1908. 
Bergeim,  Rehfuss  and  Hawk:  Jour.  Biol.  Chem.,  19,  345,  1914. 

Ivy:  Proceedings  Amer.  Physiol.  Soc.  (Amer.  Jour.  Physiol)  45,  561,  1918. 
King  and  Hanford:  Ibid.,  562. 
Sutherland:  Ibid.,  563. 

2  Hawk:  University  of  Pennsylvania  Medical  Bulletin,  18,  i,  1905. 
Fowler  and  Hawk:  Jour.  Exper.  Med.,  12,  388,  1910. 
Hattrem  and  Hawk:  Arch.  Int.  Med.,  7,  610,  1911. 

•Mattill  and  Hawk:  Jour.  Am.  Chem.  Soc.,  33,  pp.  1978,  1999,  and  2019,  1911. 
Hawk:  Arch.  Int.  Med.,  8,  382,  1911. 
Hawk:  Proceedings  Soc.  Exp.  Biol.  and  Med.,  8,  36,  1910. 
Fairhall  and  Hawk:  Jour.  Am.  Chem.  Soc.,  34,  546,  1912. 
Howe  and  Hawk:  Jour.  Biol.  Chem.,  n,  129,  1912. 
Hawk:  Biochem.  Bull.,  3,  420,   1914. 


138  PHYSIOLOGICAL  CHEMISTRY 

kinds  such  as  meat  and  bread,  the  material  instead  of  passing  to  the 
stomach,  would  invariably  find  its  way  out  of  the  animal's  body  at  the 
upper  esophageal  opening.  Through  the  medium  of  the  gastric  fistula 
the  course  of  the  secretion  of  gastric  juice  could  be  carefully  followed. 
It  was  found  that  when  the  dog  ate  meat,  for  example,  there  was  a  large 
secretion  of  gastric  juice  notwithstanding  no  portion  of  the  food  eaten 
had  reached  the  stomach.  Further  experiments  made  through  the 
medium  of  a  cul-de-sac  formed  from  the  stomach  wall  have  given  us 
many  valuable  conclusions,  among  others  those  regarding  the  influence 
of  the  chemical  stimuli.  The  method  followed  was  to  feed  the  animal 
certain  substances  and  note  the  secretion  of  gastric  juice  in  the  miniature 
stomach  while  the  real  process  of  digestion  was  taking  place  in  the 
stomach  proper. 

Normal  gastric  juice  is  a  thin,  light  colored  fluid  which  is  acid  in 
reaction  and  has  a  specific  gravity  varying  between  i.ooi  andi.oio. 
It  contains  only  0.5  per  cent  of  solid  matter  which  is  made  up  principally 
of  sodium  chlorid,  potassium  chloride,  earthy  phosphates,  mucin  and  the 
enzymes  pepsin,  gastric  rennin,  and  gastric  lipase;  the  enzymes  are  of  the 
greatest  importance.  The  acidity  of  the  gastric  juice  is  due  to  free 
hydrochloric  acid.  It  was  formerly  believed  that  this  acid  was  secreted 
by  the  parietal  cells  of  the  fundus  as  well  as  by  the  chief  cells  of  both  the 
fundus  and  pyloric  glands.  It  has  been  claimed,1  however,  that  the 
parietal  cell  is  the  seat  of  the  formation  of  the  hydrochloric  acid.  This 
conclusion  is  based  upon  the  formation  of  Prussian  blue  after  the  subcut- 
aneous injection  of  potassium  ferrocyanide  and  ammonium  ferric  citrate 
(rabbits  and  guinea-pigs)  and  the  subsequent  (3  to  30  hours)  micro- 
scopical examination  of  the  gastric  mucosa.  The  acid  was  shown  to  be 
present  in  the  lumina  of  the  gland  tubules  and  in  the  canaliculi  of  the 
parietal  cells;  traces  were  also  apparently  present  in -the  cytoplasm. 
Later  Bensley  and  Harvey2  showed  by  means  of  dyes  which  act  as  vital 
stains  and  as  indicators  very  sensitive  to  alkali  that  the  secretion  in  the 
parietal  cells  is  slightly  alkaline  whereas  that  in  the  lumen  of  the  gland 
proper  is  very  nearly  neutral.  Therefore,  the  acid  is  formed  entirely 
above  the  level  of  the  gland  proper,  i.e.,  in  the  foveolae  and  on  the  sur- 
face. Hammet3  and  still  more  recently  Macallum  and  Collip4  have 
confirmed  Miss  Fitzgerald's  claim  that  the  acid  is  formed  in  the  parietal 
cells. 

It  was  believed  that  hydrochloric  acid  was  generally  present  in  the 
gastric  juice  of  man  to  the  extent  of  about  0.2  per  cent.  When  the 

1  Fitzgerald:  Proceedings  Royal  Society  -(B),  83,  56,  1910. 

2 Bensley  and  Harvey:  Biological  Bulletin,  23,  225,  1912. 

3Hammett:  Anatomical  Record,  9,  21,  1915. 

4  Reported  before  Society  of  Biological  Chemists,  Boston,  Dec.  27,  1915-       :^-, 


GASTRIC  DIGESTION  139 

amount  of  hydrochloric  acid  varied  to  any  considerable  degree  from  this 
value  a  condition  of  hypoacidity  or  hyperacidity  was  said  to  be  es- 
tablished. On  the  basis  of  more  recent  experiments,1  however,  it 
appears  that  the  actual  acidity  of  the  gastric  juice  of  man  as  secreted 
by  the  glands  is  0.4  to  0.5  per  cent  hydrochloric  acid.  Boldyreff  be- 
lieves that  this  acidity  is  lowered  to  about  0.2  per  cent  by  regurgitation 
of  alkaline  fluid  from  the  intestine  (Chapter  VIII  on  Gastric  Analysis) . 
Hydrochloric  acid  has  the  power  of  combining  with  protein  substances 
taken  in  the  food,  thus  forming  so-called  combined  hydrochloric  acid. 
This  combined  acid  is  a  less  potent  germicide  than  free  hydrochloric 
acid  and  has  less  power  to  destroy  the  amylolytic  enzyme  salivary 
amylase  (ptyalin)  of  the  saliva.  This  last  fact  explains  to  a  degree  the 
possibility  of  the  continuance  of  salivary  digestion  in  the  stomach. 

The  term  combined  hydrochloric  acid  is  really  a  misnomer.  When 
free  hydrochloric  acid  is  treated  with  a  protein  the  latter  functions  as 
a  base  and  a  salt  is  formed.  Therefore,  instead  of  having  "com- 
bined hydrochloric  acid"  we  have  a  protein  salt  of  hydrochloric  acid. 
This  salt  ionizes  differently  from  the  free  acid.  This  fact  explains  the 
variation  in  the  germicidal  properties  of  the  two  solutions  as  well  as 
their  different  action  toward  enzymes,  such,  for  example,  as  salivary 
amylase  (see  page  60) . 

The  hydrochloric  acid  of  the  gastric,  juice  forms  a  medium  in  which 
the  pepsin  can  most  satisfactorily  digest  the  protein  food,  and  at  the 
same  time  it  acts  as  an  antiseptic  or  germicide  which  prevents  putre- 
factive processes  in  the  stomach.  It  also  possesses  slight  power  of  in- 
verting cane  sugar,  this  property  being  due  to  the  hydrogen  ion.  When 
the  hydrochloric  acid  of  the  gastric  juice  is  diminished  in  quantity 
(hypoacidity)  or  absent,  as  it  may  be  in  many  cases  of  functional  or 
organic  disease,  there  is  no  check  to  the  growth  of  micro-organisms  in 
the  stomach.  There  are,  however,  certain  of  the  more  resistant  spores 
which  even  the  normal  acidity  of  the  gastric  juice  will  not  destroy.  A 
condition  of  hypoacidity  may  also  give  rise  to  fermentation  with  the 
formation  of  comparatively  large  amounts  of  such  substances  as  lactic 
acid  and  butyric  acid. 

The  question  of  the  origin  of  the  hydrochloric  acid  of  the  gastric 
juice  is  a  problem  to  whose  solution  many  investigators  have  given 
much  attention.     Many  theories  have  been  proposed,  among  them  the 
interaction  of  sodium  chloride  with  carbonic  acid,2  with  acid  phosphate8 
xBabkin:  Die  aussere  Sekretion  der  VerdauungsdrUsen,  Berlin,  1914,  p,  113. 
Boldyreff:  Quart.  Jour.  Exper.  Physiol.,  8,  i,  1914- 
Carlson:  Am.  Jour.  Physiol.,  38,  248,  1915. 
'Bunge:  Physiologic  and  Pathologic  Chemistry,  2nd.  Eng.  Ed.,  Philadelphia,  1902,  p. 

aMaly:  Zeit.  f.  physioL  Chem.,  i,  174,  1877.  Macallum  and  Collip:  Reported  before 
the  Society  of  Biological  Chemists,  Boston,  Dec.  27,  1915. 


140  PHYSIOLOGICAL   CHEMISTRY 

or  with  organic  acids.  On  the  other  hand,  it  is  possible  that  hydro- 
chloric acid  is  set  free  from  combination  with  some  weak  base  as 
ammonia1  or  that  free  phosphoric  acid  valences  may  be  set  free  by  the 
enzymic  hydrolysis  of  organic  phosphoric  acid  esters.2  We  cannot  go 
into  a  discussion  of  these  various  theories.  That  the  hydrochloric 
acid  arises  from  the  chlorides  of  the  blood  appears  to  be  well  established 
but  the  same  cannot  be  said  with  regard  to  the  immediate  or  ultimate 
origin  of  the  hydrogen  ions  involved  in  the  reaction. 

The  most  important  of  the  enzymes  of  the  gastric  juice  is  the  pro- 
teolytic  enzyme  pepsin.  The  pepsin  does  not  originate  as  such  in  the 
gastric  cells  but  is  formed  from  its  precursor,  the  zymogen  or  mother- 
substance  pepsinogen,  which  is  apparently  produced  by  the  parietal 
cells  of  the  fundus  as  well  as  by  the  chief  cells  of  the  fundus  and  pyloric 
glands.  Pepsinogen  may  be  differentiated  from  pepsin  from  the  fact 
that  it  is  more  resistant  to  alkali.3  Upon  coming  into  contact  with  the 
hydrochloric  acid  of  the  secretion  this  pepsinogen  is  immediately  trans- 
formed into  pepsin.  Pepsin  is  not  active  in  alkaline  or  neutral  solutions, 
but  requires  at  least  a  faint  acidity  before  it  can  exert  its  power  to  dis- 
solve and  digest  proteins.  The  percentage  of  hydrochloric  acid  facili- 
tating the  most  rapid  peptic  action  varies  with  the  character  of  the 
protein  acted  upon,  e.g.,  0.08  per  cent  to  o.i  per  cent  for  the  digestion  of 
fibrin  and  0.25  per  cent  for  the  digestion  of  coagulated  egg-white. 
While  hydrochloric  acid  is  the  acid  usually  employed  to  promote  arti- 
ficial peptic  proteolysis,  other  acids,  organic  and  inorganic,  will  serve  the 
same  purpose.  Acidity  of  the  liquid  is  necessary  to  promote  the 
activity  of  the  pepsin,  but  the  acidity  need  not  necessarily  be  confined 
to  hydrochloric  acid. 

In  common  with  many  other  enzymes  pepsin  acts  best  at  about 
38°-4o°C.  and  its  digestive  power  decreases  as  the  temperature  is  low- 
ered, the  enzyme  being  only  slightly  active  at  o°C.  Its  power  is  only 
temporarily  inhibited  by  the  application  of  such  low  temperatures, 
however,  and  the  enzyme  regains  its  full  proteolytic  power  upon  rais- 
ing the  temperature  to  4o°C.  As  the  temperature  of  a  digestive  mix- 
ture is  raised  above  40° C.  the  pepsin  gradually  loses  its  activity 
until  at  about  8o°-ioo°C.  its  proteolytic  power  is  permanently 
destroyed. 

Our  ideate  regarding  the  nature  of  the  products  formed  in  the  course 
of  peptic  proteolysis  have  undergone  considerable  revision  in  recent 
years.  The  former  view  that  these  products  included  only  acid  albu- 
minate  (acid  metaprotein),  proteoses,  peptones  and  peptides  is  no 

1Mathews:  Physiological  Chemistry,  New  York,  1915,  p.  374. 
•Bergeim:  Proc.  Soc.  Exp.  Biol.  and  Med.,  12,  21,  1914. 
'Langley:  Jour,  of  PhysioL,  3,  246. 


GASTRIC  DIGESTION  141 

longer  tenable.  From  the  investigations  of  numerous  observers  we 
have  learned  that  artificial  gastric  digestion  if  permitted  to  proceed  for  a 
sufficiently  long  period  will  yield,  in  addition  to  proteoses,  peptones  and 
peptides,  a  long  list  of  protein  cleavage  products  which  are  crystalline 
in  character,  including  leucine,  tyrosine,  alanine,  phenylalanine,  aspartic 
acid,  glutamic  acid,  proline,  leucinimide,  valine,  and  lysine.  A  similar 
group  of  substances  may  result  from  the  action  of  the  enzyme  trypsin 
(see  page  189).  The  relative  amounts  of  proteoses,  peptones,  and  crys- 
talline substances  formed  depends  to  a  great  extent  upon  the  character 
of  the  protein  undergoing  digestion,  e.g.,  a  greater  proportion  of  pro- 
teoses results  from  the  digestion  of  fibrin  than  from  the  digestion  of 
coagulated  egg-white.  We  must  not  be  led  into  the  error  of  thinking 
that  the  large  number  of  protein  cleavage  products  just  mentioned  are 
formed  in  the  course  of  normal  gastric  digestion  within  the  animal 
organism.  They  are  formed  only  after  comparatively  long-continued 
hydrolysis.  In  pancreatic  digestion,  however,  there  are  formed  even 
under  normal  conditions  the  large  number  of  cleavage  products  to 
which  reference  has  been  made.  Peptic  proteolysis,  therefore,  within 
the  animal  organism  differs  from  tryptic  proteolysis  (see  page  189) 
in  that  the  former  yields  larger  amounts  of  proteoses,  smaller  amounts 
of  peptones  and  no  considerable  quantity  of  crystalline  bodies  as  end- 
products  in  the  brief  period  during  which  proteins  are  ordinarily  sub- 
jected to  gastric  digestion.  Prolonged  hydrolysis  with  gastric  juice 
does,  however,  yield  considerable  quantities  of  the  non-protein  end- 
products.  In  cases  of  cancer  of  the  stomach  a  peptide-splitting 
enzyme  (erepsin)  is  said  to  be  present  in  the  stomach  contents.  This 
enzyme  is  believed  to  be  elaborated  by  the  cancer  tissue  and  its  identi- 
fication is  of  importance  in  connection  with  the  diagnosis  of  gastric 
cancer.  The  glycyl-trytophane  test1  is  sometimes  used  for  this 
purpose.  This  test  has  been  very  severely  criticized  (see  page  202). 
Abderhalden  and  Meyer2  have  shown  active  pepsin  to  be  present 
in  the  contents  of  all  parts  of  the  small  intestine.  It  is  suggested  that 
pepsin  may  be  adsorbed  in  the  stomach  by  such  protein  substances 
as  pass  into  the  intestine  in  solid  form  and  that  the  pepsin  thus  pro- 
tected may  bring  about  gastric  digestion  whenever  the  reaction  of  the 
surrounding  intestinal  contents  is  favorable.  This  fact  may  be  of 
importance  in  connection  with  the  profound  proteolysis  taking  place 
in  the  intestine.  Heretofore,  this  process  was  believed  to  be  furthered 
alone  by  trypsin  and  erepsin.  The  passage  of  adsorbed  pepsin  into  the 
intestine  may  be  an  efficient  aid  to  the  proper  digestion  of  solid  proteins 

lNeubauer  and  Fischer:  Deut.  Arch.  f.  klin.  Med.,  97,  499,  1909. 
2  Abderhalden  and  Meyer:  Zeit.fur  physiol.  Chem.,  74,  67,  1911. 


142  PHYSIOLOGICAL   CHEMISTRY 

which  are  ingested  without  sufficient  mastication  ("  bolted  ")*  and  which 
consequently,  at  times,  pass  into  the  intestine  in  rather  large  pieces 
(see  Chapter  XIV  on  Feces). 

Gastric  rennin,  the  second  enzyme  of  the  gastric  juice,  is  what  is 
known  as  a  milk  curdling  or  protein  coagulating  enzyme.  Rennin  acts 
upon  the  casein  of  the  milk,  splitting  it  into  a  peptone-like  body  and 
soluble  paracasein.  This  soluble  body,  in  the  presence  of  calcium 
salts,  combines  with  calcium,  forming  calcium  paracasein  which  is 
insoluble  and  precipitates.  There  is  some  uncertainty  regarding 
the  reaction  to  litmus  in  which  gastric  rennin  shows  the  greatest 
activity.  It  is,  however,  said  to  be  active  in  neutral,  alkaline,  or  acid 
solution.  However,  it  probably  possesses  its  greatest  activity  in  the 
presence  of  a  slight  acid  reaction,  as  would  naturally  be  expected.  It 
is  especially  abundant  in  the  gastric  mucosa  of  the  calf,  and  is  used 
to  curdle  the  milk  used  in  cheese  making.  Gastric  rennin  is  always 
present  normally  in  the  gastric  juice,  but  in  certain  pathological  con- 
ditions such  as  atrophy  of  the  mucosa,  chronic  catarrh  of  the  stomach, 
or  in  carcinoma  it  may  be  absent. 

The  theory  that  the  proteolytic  activity  and  the  milk  curdling  prop- 
erty of  the  gastric  juice  reside  in  a  single  substance,  is  causing  much 
controversy  at  the  present  time.  The  theory  was  originally  advanced 
by  the  Pawlow  school.2  According  to  Nencki  and  Sieber,3  the  milk 
curdling  and  protein  hydrolyzing  activities  reside  in  definite  and  distinct 
side  chains  of  a  single  mammoth  molecule.  The  view  which  has  rather 
the  strongest  support,  however,  is  to  the  effect  that  there  are  two  entirely 
distinct  enzymes.  Important  evidence  has  been  advanced  in  favor  of 
this  view  of  Hammarsten,4  Taylor,5  and  Hemmeter.6  Burge7  has  re- 
ported experiments  upon  the  influence  of  a  direct  electric  current  upon 
solutions  possessing  typical  rennin  and  peptic  activities.  By  this 
means  he  was  able  to  prepare  a  solution  possessing  strong  rennin 
activity  but  entirely  devoid  of  peptic  activity.  This  furnishes  strong 
evidence  against  the  identity  of  the  two  enzymes  but  does  not  neces- 
sarily deny  the  accuracy  of  the  side-chain  theory. 

Gastric  lipase,  the  third  enzyme  of  the  gastric  juice,  is  a  fat-splitting 
enzyme.  It  possesses  but  slight  activity  when  the  gastric  juice  is  of 
normal  acidity,  but  evinces  its  action  principally  at  such  times  as  a 

1  Foster  and  Hawk:  Proceedings  of  the  Eighth  International  Congress  of  Applied  Chem- 
istry, New  York,  September,  1912. 

2 Pawlow  and  Parastschuk:  Zeitschrift  fur  Physiologische  Chemie,  42,  415,  1904. 

3  Nencki  and  Sieber:  Zeitschrift  fur  Physiologische  Chemie,  23,  191,  1901. 

4  Hammarsten :  Zeitschrift  fur  Physiologische  Chemie,  56,  18,  1908;  94,  291,  1915. 

5  Taylor:  Journal  of  Biological  Chemistry,  5,  399,  1909. 

8 Hemmeter:  Berliner  klinische  Wochenschrtft,  Ewald  Festnummer,  44,  1905. 
7  Burge:  American  Journal  of  Physiology,  29,  1912. 


.  GASTRIC   DIGESTION  143 

gastric  juice  of  low  acidity  is  secreted  either  from  physiological  or  patho- 
logical cause.  The  digestion  of  fat  in  the  stomach  is,  however,  at 
most,  of  but  slight  importance  as  compared  with  the  digestion  of  fat  in 
the  intestine  through  the  action  of  the  lipase  of  the  pancreatic  juice 
(seepage  192). 

Boldyreff 1  has  shown  trypsin  to  be  present  in  stomach  contents,  due 
to  regurgitation  of  intestinal  contents  through  the  pylorus.  This  claim 
has  been  verified  by  others2  (see  Chapter  VIII  on  Gastric  Analysis). 

The  gastric  response3  to  different  foods  varies  widely.  There  is 
also  a  great  variation  in  normal  stomachs.  Some  such  stomachs  empty 
slowly,  others  rapidly — some  give  high  acidities,  others  low  acidities. 

COLLECTION  OF  HUMAN  GASTRIC  JUICE 

,  Have  one  or  more  volunteers  from  the  class  take^  the  Rehfuss  Stomach  Tube 
as  directed  on  page  162.  The  subjects  must  omit  breakfast  if  the  tube  is  taken 
in  the  morning  or  luncheon  if  taken  in  the  afternoon.  Empty  the  stomach 
(see  pp.  163-4)  and,  with  the  tube  still  in  place,  allow  each  subject  to  drink 
250  c.c.  of  water.  The  water  will  stimulate  the  flow  of  gastric  juice  and  will 
itself  quickly  leave  the  stomach.  In  many  instances  fairly  concentrated  gastric 
juice  may  be  obtained  from  the  stomach  in  from  30  to  45  minutes  after  the 
introduction  of  the  water.  Remove  this  gastric  juice  according  to  procedure 
outlined  on  pp.  164-5.  For  composition  of  human  gastric  juice  see  page  155. 
See  also  Experiment  n,  page  149.  If  thought  desirable  the  gastric  juice  result- 
ing from  psychical  stimulation  (see  page  149)  may  be  collected  instead  of  that 
following  the  chemical  stimulation  of  water.  (Curves  showing  the  stimulatory 
power  of  water  are  given  in  Figs.  41  and  42.) 

PREPARATION  OF  AN  ARTIFICIAL  GASTRIC  JUICE 

Dissect  the  mucous  membrane  of  a  pig's  stomach  from  the  muscular  por- 
tion and  discard  the  latter.  Divide  the  mucous  membrane  into  two  parts  (4/5 
and  1/5).  Cut  up  the  larger  portion  place  it  in  a  large-sized  beaker  with  0.4 

Boldyreff:  Quart.  Jour.  Exper.  PhysioL,  8,  i,  1914. 

2Spencer  Meyer,  Rehfuss  and  Hawk:  Am.  Jour.  PhysioL,  39,  459,  1916. 

3 1.  Intragastric  Conductance — Bergeim:  Am.  J.  PhysioL,  45,  i,  1917. 

II.  Milk — Bergeim,  Evvard,  Rehfuss,  Hawk:  Am.  J.  Physiol.,  48,  411,  1919- 

III.  Beef— Fishback,  Smith,  Bergeim,  Lichtenthaeler,  Rehfuss,  Hawk;  Am.  J.  PhysioL, 
49,  174,  1919. 

IV.  Pork — Smith,  Fishback,  Bergeim,  Rehfuss,  Hawk:  Am.  J.  PhysioL,  49,  204,  1919. 
V.  Lamb — Fishback,  Smith,  Bergeim,  Rehfuss,  Hawk:  Am.  J.  PhysioL,  49,  222,  1919. 

VI.  Eggs — Miller,  Fowler,  Bergeim,  Rehfuss,  Hawk:  Am.  J.  PhysioL,  49,  254,  1919. 
VII.  Vegetables— Miller,  Fowler,  Bergeim,  Rehfuss,  Hawk:  Am.  J.  PhysioL,   51,  332, 
1920. 

VIII.  Unpalatable  Food — Holder,  Smith,  Hawk:  Set.,  51,  299,  1920. 
IX.  Influence  of  Worry — Miller,  Bergeim,  Hawk:  Sci.,  52,  253,  1920. 
X.  Psychic  Secretion — Miller,  Bergeim,  Rehfuss,  Hawk:  Am.  J.  PhysioL,  52,  i,  1920. 
XI.  Tea,  Coffee,  Cocoa— Miller,  Bergeim,  Rehfuss,  Hawk:  Am.  J.  PhysioL,  52,  28, 
1920. 

XII.  Pies,  Cakes,  Puddings— Miller,  Fowler,  Bergeim,  Rehfuss,  Hawk:  Am.  J.  PhysioL, 
52,  248,  1920. 

XIII.  Sugars  and  Candies— Miller,  Bergeim,  Rehfuss,  Hawk:  Am.  J.  PhysioL,  53,  65, 
1920. 


144 


PHYSIOLOGICAL  CHEMISTRY 


per  cent  hydrochloric  acid  and  keep  at  38°-4O°C.  for  at  least  24  hours.  Filter 
off  the  residue,  consisting  of  nuclein  and  other  substances,  and  use  the  filtrate 
as  an  artificial  gastric  juice.  This  filtrate  contains  pepsin,  rennin,  and  the 
products  of  the  digestion  of  the  stomach  tissues,  i.e.,  acid  metaprotein  (acid 
albuminate),  proteoses,  peptones,  etc. 

PREPARATION  OF  A  GLYCEROL  EXTRACT  OF  PIG'S  STOMACH 

Take  the  one-fifth  portion  of  the  mucuos  membrane  of  the  pig's  stomach  not 
used  in  the  preparation  of  the  artificial  gastric  juice,  cut  it  up  finely,  place  it 

Acidity IZO 

C.C.%,NaOH.,lo. 


100 
90- 
60- 
70- 
60- 
50- 
40- 
30- 
20 
10- 


0 

Time 
Interval 
-minutes 


Acidity 
100 

90- 
60 
70- 
60- 
50 
40- 
30- 
ZO- 
10- 


10      20     30    40     50    60 
500c.c.  coo/(io-iz°c)  city  water 
at  1  P.M.  6  hrs.  after  lax  meal 
Subject  J.T.L. 

FI<J.  41. — CURVES  SHOWING  STIMULATORY 

POWER  OF  WATER. 

(Bergeim,  Rehfuss  and  Hawk:  Journal  Bio- 
logical Chemistry,  19,  345,  1914.) 


P 

Time 
Interval 


Pepsin 


.--— ?~e£s.'H._ 


10      tO      30      40      50      60 

minutes 

400c.c.  water  SZhours  after  an 
Ewa/d  meal-   Subject  O.B. 

FIG.  42. — CURVES  SHOWING  STIMULAT- 
ORY POWER  OF  WATER. 
(Bergeim,  Rehfuss  and  Hawk:  Journal 
Biological  Chemistry,  19,  345, 1914.) 


in  a  small-sized  beaker  and  cover  the  membrane  with  glycerol.  Stir  frequently 
and  allow  to  stand  at  room  temperature  for  at  least  24  hours.  The  glycerol  will 
extract  the  pepsinogen.  Separate,  with  a  pipette  or  by  other  means,  the  glycerol 
from  the  pieces  of  mucous  membrane  and  use  the  glycerol  extract  as  required  in 
the  later  experiments. 

PRODUCTS  or  GASTRIC  DIGESTION 

Into  the  artificial  gastric  juice,  prepared  as  above  described,  place  the  protein 
material  (fibrin,  coagulated  egg-white,  or  lean  beef)  provided  for  you  by  the 
instructor,  add  0.4  per  cent  hydrochloric  acid  as  suggested  by  the  instructor  and 
keep  the  digestion  mixture  at  4O°C.  for  two  to  three  days.  Stir  frequently  and 
keep  free  hydrochloric  acid  present  in  the  solution  (for  tests  for  free  hydro- 
chloric acid  see  page  156). 


GASTRIC  DIGESTION  145 

The  original  protein  has  been  digested  and  the  solution  now  contains  the 
products  of  peptic  proteolysis,  i.e.,  acid  metaprotein  (acid  albuminate),  proteoses, 
peptones,  etc.  The  insoluble  residue  may  include  nuclein  and  other  substances. 
Filter  the  digestion  mixture  and  after  testing  for  free  hydrochloric  acid  neutralize 
the  filtrate  with  potassium  hydroxide  solution.  If  any  of  the  acid  metaprotein 
(acid  albuminate)  is  still  untransformed  into  proteoses  it  will  precipitate  upon 
neutralization.  If  any  precipitate  forms  heat  the  mixture  to  boiling,  and  filter. 
If  no  precipitate  forms  proceed  without  filtering. 

We  now  have  a  solution  containing  a  mixture  consisting  principally  of  pro- 
teoses and  peptones.  Separate  and  identify  the  proteoses  and  peptones  ac- 
cording to  the  directions  given  on  pages  118  and  119. 

GENERAL  EXPERIMENTS  ON  GASTRIC  DIGESTION 

1.  Conditions  Essential  for  the  Action  of  Pepsin. — Prepare  four  test-tubes  as 
follows : 

(a)  Five  c.c.  of  pepsin  solution. 

(b)  Five  c.c.  of  0.4  per  cent  hydrochloric  acid. 

(c)  Five  c.c.  of  pepsin-hydrochloric  acid  solution. 

(d)  Two  or  3  c.c.  of  pepsin  solution  and  2-3  c.c.  of  0.5  per  cent  sodium  car- 
bonate solution. 

Introduce  into  each  tube  a  small  piece  of  fibrin  and  place  them  in  the  incu- 
bator or  water-bath  at  4O°C.  for  one-half  hour,  carefully  noting  any  changes  which 
occur.1  (Carmine-fibrin  may  be  used  to  advantage  in  this  and  the  following  tests 
under  Gastric  Digestion.  In  this  case,  however,  the  experiments  should  be  con- 
ducted at  room  temperature.  For  directions  as  to  the  preparation  of  carmine- 
fibrin  see  Chapter  I.)  Now  combine  the  contents  of  tubes  (a)  and  (b)  and 
see  if  any  further  change  occurs  after  standing  at  4O°C.  for  15-20  minutes.  Ex- 
plain the  results  obtained  from  these  five  experiments. 

2.  Influence  of  Different  Temperatures. — In  each  of  four  test-tubes  place  5 
c.c.  of  pepsin-hydrochloric  acid  solution.    Immerse  one  tube  in  cold  water  from 
the  faucet,  keep  a  second  tube  at  room  temperature  and  place  a  third  in  the 
incubator  or  water-bath  at  4O°C.    Boil  the  contents  of  the  fourth  tube  for  a 
few  moments,  then  cool  and  also  keep  it  at  4O°C.    Into  each  tube  introduce  a 
small  piece  of  fibrin  and  note  the  progress  of  digestion.    In  which  tube  does  the 
most  rapid  digestion  occur?    Explain  this. 

3.  The  Most  Favorable  Acidity. — Prepare  three  tubes  as  follows : 

(a)  Five  c.c.  of  0.2  per  cent  pepsin-hydrochloric  acid  solution. 

(b)  Two  or  3  c.c.  of  0.2  per  cent  hydrochloric  acid  +  i  c.c.  of  concentrated 
hydrochloric  acid  +  5  c.c.  pepsin  solution. 

(c)  One  c.c.  of  0.2  per  cent  pepsin-hydrochloric  acid  solution  -f  5  c.c.  of 
water. 

Introduce  a  small  piece  of  fibrin  into  each  tube,  keep  them  at  4o°C.,  and  note 

1  Digestion  of  fibrin  in  a  pepsin-hydrochloric  acid  solution  is  indicated  first  by  a  swelling 
of  the  protein  due  to  the  action  of  the  acid,  and  later  by  a  disintegration  and  dissolving  of 
the  fibrin  due  to  the  action  of  the  pepsin-hydrochloric  acid.  If  uncertain  at  any  time 
whether  digestion  has  taken  place,  the  solution  under  examination  may  be  filtered  and  the 
biuret  test  applied  to  the  filtrate.  A  positive  reaction  will  signify  the  presence  of  acid 
metaprotein  (acid  albuminate),  proteoses  (albumoses),  or  peptones,  the  presence  of  any 
one  of  which  would  indicate  that  digestion  has  taken  place. 


146  PHYSIOLOGICAL   CHEMISTRY 

I 

the  progress  of  digestion.    In  which  degree  of  acidity  does  the  fibrin  digest  the 
most  rapidly? 

4.  Differentiation  between  Pepsin  and  Pepsinogen. — Prepare  five  tubes  as 
follows : 

(a)  Few  drops  of  glycerol  extract  of  pepsinogen  +  2-3  c.c.  of  water. 

(b)  Few  drops  of  glycerol  extract  of  pepsinogen  +  5  c.c.  of  0.2  per  cent  hydro- 
chloric acid. 

(c)  Few  drops  of  glycerol  extract  of  pepsinogen  -f  5  c.c.  of  0.5  per  cent  sodium 
carbonate. 

(d)  Two  or  3  c.c.  of  pepsin  solution  +  2-3  c.c.  of  i  per  cent  sodium  carbonate. 

(e)  Few  drops  of  glycerol  extract  of  pepsinogen  +  5  c.c.  of  i  per  cent  sodium 
carbonate. 

Add  a  small  piece  of  fibrin  to  the  contents  of  each  tube,  keep  the  five  tubes  at 
4O°C.  for  one-half  hour  and  observe  any  changes  which  may  have  occurred.  To 
(a)  add  an  equal  volume  of  0.4  per  cent  hydrochloric  acid,  neutralize  (c),  (d)  and 
(e)  with  hydrochloric  acid  and  add  an  equal  volume  of  0.4  per  cent  hydrochloric 
acid.  Place  these  tubes  at  4O°C.  again  and  note  any  further  changes  which  may 
occur.  What  contrast  do  we  find  in  the  results  from  the  last  three  tubes? 
On  the  basis  of  these  tests  what  is  the  relative  resistance  of  pepsin  and  pepsinogen 
to  alkalis? 

5.  Comparative  Digestive  Power  of  Pepsin  with  Different  Acids. — Prepare  a 
series  of  tubes  each  containing  a  N/io  solution  of  one  of  the  following  acids: 
hydrochloric,  sulphuric,  nitric,  combined  hydrochloric,  acetic,  lactic  and  oxalic. 
To  each  acid  add  a  few  drops  of  the  glycerol  extract  of  pig's  stomach  and  a  small 
piece  of  fibrin.     Shake  well,  place  at  4O°C.,  and  note  the  progress  of  digestion. 
In  which  tubes  does  the  most  rapid  digestion  occur? 

6.  Influence  of  Metallic  Salts,  etc. — Prepare  a  series  of  tubes  and  into  each 
tube  introduce  4  c.c.  of  pepsin-hydrochloric  acid  solution  and  0.5  c.c.  of  one  of  the 
chemicals  listed  in  Experiment  19  under  Salivary  Digestion,  page  60.    Introduce  a 
small  piece  of  fibrin  into  each  of  the  tubes  and  keep  them  at  40° C.  for  one-half  hour. 
Note  the  variations  in  the  progress  of  digestion.    Where  has  the  least  rapid  diges- 
tion occurred? 

7.  Sahli's  Desmoid  Reaction.— This  is  a  method  for  testing  gastric  function 
without  using  the  stomach  tube.    The  underlying  principle  of  the  test  is  the  fact 
that  raw  catgut  may  be  digested  in  gastric  juice  but  is  entirely  indigestible  in 
pancreatic  juice.    The  test  is  made  as  follows :    A  methylene-blue  pill  is  intro- 
duced into  a  small  rubber  bag  and  the  mouth  of  the  bag  subsequently  tied  with 
catgut. l    The  small  bag  is  then  ingested  immediately  after  the  mid-day  meal  and 
the  urine  examined  5,  7,  9  and  18-20  hours  later  for  methylene  blue.    If  methyl- 
ene  blue  is  present  in  appreciable  quantity,  it  will  impart  to  the  urine  a  greenish- 
blue  color.  If  not  present  in  sufficient  amount  to  impart  this  color  the  urine  should 
be  boiled  with  one-fifth  its  volume  of  glacial  acetic  acid,  whereupon  a  greenish- 
blue  color  results  if  the  chromogen  of  methylene  blue  is  present.    This  contin- 
gency seldom  arises,  however,  inasmuch  as  in  most  cases  of  uncolored  urine  it  will 

1  About  0.05  gram  of  methylene  blue  is  mixed  with  sufficient  ext.  glycyrrhiza  to  form 
a  pill  about  3-4  mm.  in  diameter.  The  pill  is  then  placed  in  the  center  of  a  square  piece 
of  thin  rubber  dam  and  a  little  bag-like  receptacle  constructed  by  a  twisting  movement. 
The  neck  of  the  bag  is  then  closed  by  wrapping  three  turns  of  catgut  about  it.  The 
most  satisfactory  catgut  to  use  is  number  oo  raw  catgut  which  has  previously  been  soaked 
in  water  until  soft.  When  ready  for  use  the  bag  should  sink  instantly  when  placed  in 
water  and  be  water-tight. 


GASTRIC  DIGESTION 


147 


be  found  that  the  rubber  bag  has  passed  through  the  stomach  unopened.  If  the 
methylene  blue  is  found  in  the  urine  inside  of  18-20  hours  a  satisfactory  gastric 
function  is  indicated. 

For  Einhorn's  bead  method  for  the  study  of  digestive  function  see  chapter  on 
Feces. 

8.  Testing  the  Motor  and  Functional  Activities  of  the  Stomach.— This 
test  is  performed  the  same  as  Experiment  20  under  Salivary  Digestion,  page  60. 
If  the  experiment  was  carried  out  under  salivary  digestion  it  will  not  be  neces- 
sary to  repeat  it  here. 


cc 


96 


6C 


Wnfca. 


FIG.  43.— CURVES  SHOWING  STIMULATORY  POWER  OF  BEEF  EXTRACT 
(Plotted  from  unpublished  data  collected  in  the  author's  laboratory  by  Professor  Chester  C. 

Fowler.} 


This  test  does  not  serve  as  an  index  of  gastric  absorption  as  is  sometimes  stated. 
It  has  been  shown  by  von  Mering,  for  example,  that  potassium  iodide  is  not  ab- 
sorbed from  the  stomach  for  2-3  hours.  Hence  when  iodine  appears  in  the  saliva 
a  few  minutes  after  the  KI  is  ingested  this  fact  would  indicate  absorption  from  the 
intestine.  The  gastric  mucosa  is  not  importantly  related  to  absorption. 

9.   Influence  of  Bile.— Prepare  three  tubes  as  follows: 

(a)  Five  c.c.  of  pepsin-hydrochloric  acid  solution  +  0.5-1  c.c.  of  bile. 

(b)  Five  c.c.  of  pepsin-hydrochloric  acid  solution  -f  5  c.c.  of  bile. 

(c)  Five  c.c.  of  pepsin-hydrochloric  acid  solution. 


148 


PHYSIOLOGICAL    CHEMISTRY 


Introduce  into  each  tube  a  small  piece  of  fibrin.  Keep  the  tubes 
at  4o°C.  and  note  the  progress  of  digestion.  Does  the  bile  exert  any 
appreciable  influence?  How? 

10.  Influence  of  Gastric  Rennin  on  Milk. — Prepare  a  series  of  five  tubes  as 
follows : 

(a)  Five  c.c.  of  fresh  milk  -f  0.2  per  cent  hydrochloric  acid  (add  slowly  until 
precipitate  forms). 


Time 


I  houi 


FIG.  44.— CURVES  SHOWING  PSYCHICAL  STIMULATION  OF  GASTRIC  SECRETION 
(Plotted  from  unpublished  data  in  the  author's  laboratory  by 
Dr.  Raymond  J.  Miller.) 

(b)  Five  c.c.  of  fresh  milk  +  5  drops  of  rennin  solution.1 

(c)  Five  c.c.  of  fresh  milk  +  10  drops  of  0.5  per  cent  sodium  carbonate  solu- 
tion. 

(d)  Five  c.c.  of  fresh  milk  -f  10  drops  of  a  saturated  solution  of  ammonium 
oxalate. 

lAny  good  commercial  rennin  or  rennet  preparation  may  be  used  in  preparing  this 
solution. 


GASTRIC    DIGESTION  149 

(e)  Five  c.c.  of  fresh  milk  +  5  drops  of  0.2  per  cent  hydrochloric  acid.  Now  to 
each  of  the  tubes  (c),  (d),  and  (e)  add  5  drops  of  rennin  solution.  Place  the  whole 
series  of  five  tubes  at  4O°C.  and  after  10-15  minutes  note  what  is  occurring  in  the 
different  tubes.  Give  a  reason  for  each  particular  result.  How  do  ammonium 
oxalate  and  sodium  carbonate  prevent  coagulation? 

11.  Characteristics  of  Human  Gastric  Juice. — Take  some  of  the  human 
gastric  juice  collected  as  described  on  page  143  and  show  that  it  is  acid  hi  re- 
action, that  it  contains  chlorides  and  that  it  has  the  power  to  digest  protein 
material  and  to  curdle  milk. 

12.  Chemical  Stimulation  of  Gastric  Secretion. — Have  one  or  more  volunteers 
from  the  class  take  the  Rehfuss  Stomach  Tube  as  directed  on  page  162.    The 
subjects  must  omit  breakfast  if  the  tube  is  taken  in  the  morning  or  luncheon 
if  taken  in  the  afternoon.    Empty  the  stomach  (see  pp.  163-4)  aad*  with  the  tube 
still  in  position,  allow  each  subject  to  drink  250  c.c.  of  bouillon  prepared  by 
dissolving  one  bouillon  cube  in  hot  water.     Collect  samples  of  gastric  contents 
at  intervals  until  the  stomach  is  empty  as  described  under  5  on  page  164.    The 
samples  thus  collected  may  be  examined  qualitatively  for  acid,  chlorides,  pepsin 
and  rennin  or  they  may  be  submitted  to  the  quantitative  procedure  given  under  6 
on  page  165.    If  the  examination  is  made  quantitative  the  data  may  be  recorded 
in  the  form  of  a  curve  such  as  shown  in  Fig.  43,  page  147. 

13.  Psychical  Stimulation  of  Gastric  Secretion. — Have  one  or  moro  volunteers 
from  the  class  take  the  Rehfuss  Stomach  Tube  as  directed  on  page  162.    The 
subjects  must  omit  breakfast  if  the  tube  is  taken  in  the  morning  or  luncheon 
if  taken  in  the  afternoon.    Empty  the  stomach  (see  pp.  163-4)  ^d  while  the 
tube  is  still  in  position  permit  the  subjects  to  see  and  smell  an  appetizing  beef- 
steak while  it  is  being  cooked.    They  may-  also  be  permitted  to  taste  some  of 
the  material  provided  care  is  taken  that  none  is  swallowed.    Empty  the  stomach 
completely  at  10  minute  intervals  as  described  under  5  on  page  164.    Measure 
the  volume  of  each  sample  and  examine  them  qualitatively  for  acid,  chlorides, 
pepsin  and  rennin.    If  preferred  the  quantitative  procedure  given  under  6  on 
page  165  may  be  substituted  for  the  qualitative  examination.     On  the  basis 
of  the  quantitative  data  a  curve  such  as  shown  on  page  148  may  be  constructed. 

14.  Automatic  Regulation  of  Gastric  Acidity. — Have  one  or  more  volunteers 
from  the  class  take  the  Rehfuss  Stomach  Tube  as  directed  on  page  162.    The 
subjects  must  omit  breakfast  if  the  tube  is  taken  in  the  morning  or  luncheon 
if  taken  in  the  afternoon.    Empty  the  stomach  (see  pp.  163-4)  and,  with  the 
tube  still  in  position,  introduce  100  c.c.  of  0.5  per  cent  HC1  through  the  tube  by 
means  of  a  syringe.    Withdraw  samples  of  stomach  contents  at  15  minute 
intervals,  until  the  stomach  is  empty,  as  described  on  page  164.    A  qualitative 
examination  of  the  samples  will  indicate  a  progressive  decrease  in  acidity  until 
an  acid  concentration  in  the  neighborhood  of  0.2-0.3  per  cent  is  reached.    Trypsin 
(p.  171)  and  bile  (p.  174)  may  also  be  shown  to  be  present,  in  at  least  some  of 
the  samples,  thus  indicating  regurgitation  from  the  duodenum.    If  it  is  desired 
to  make  the  examination  quantitative  the  procedure  described  on  page  165, 
section  6,  may  be  followed.    From  the  data  thus  determined  a  curve  such  as 
that  shown  in  Fig.  49,  page  153,  may  be  constructed.     (For  a  discussion  of 
regurgitation  see  pages  153  and  154.) 


CHAPTER  VIII 
GASTRIC  ANALYSIS 

The  method  of  gastric  analysis  which  has  been  in  vogue  clinically 
for  years  (see  page  176)  entails  the  feeding  of  a  standard  test  meal, 
the  removal  of  the  complete  stomach  contents  at  the  end  of  a  one- 
hour  period ,  and  the  analysis  of  the  material  so  removed.  That  this 
method  is  inaccurate  has  been  repeatedly  demonstrated  in  the  author's 
laboratory1  and  elsewhere.2  Furthermore,  owing  to  the  bulk  of  the 
old  form  of  stomach  tube  and  the  discomfort  occasioned  by  its  use,  it 
is  impossible  to  follow  the  whole  cycle  of  digestion  and  estimate,  step 


Tot. 
Ac. 

N/10 
NaOH 


60 
30 


Time 


Ihr. 


2hr. 


FIG.  45. — NORMAL  AND  PATHOLOGICAL  CURVES  AFTER  AN  EWALD  MEAL. 

i,  normal  curve;  2,  delayed  digestion  with  late  hyperacidity;  3,  larval  hyperacidity; 

4,  tardive  hyperacidity;  5,  marked  continued  secretion  from  obstruction. 

by  step,  the  exact  changes  which  take  place  in  the  stomach  after  the 
introduction  of  definite  food  mixtures  into  that  organ. 

Realizing  the  inadequacy  of  the  procedure  entailed  in  the  old 
method  of  gastric  analysis,  a  new  procedure  has  been  developed  by  Dr. 
Martin  E.  Rehfuss  in  the  author's  laboratory.  This  so-called  "Frac- 
tional Method"  entails  the  analysis  of  samples  of  material  withdrawn 
from  the  stomach  (by  syringe)  at  short  intervals  for  a  period  of  two 
hours  or  more  (until  stomach  is  empty)  after  the  ingestion  of  the  test 
meal.  By  this  means  the  observer  is  able  to  follow  the  entire  cycle  of 

1  Rehfuss:  Jour.  Am.  Med.  Ass'n,  64,  569,  1914. 

Rehfuss,  Bergeim  and  Hawk:  Jour.  Am.  Med.  Ass'n,  63,  909,  1914. 

Bergeim,  Rehfuss  and  Hawk:  Jour.  Am.  Med.  Ass'n,  63,  n,  1914. 
*  Harmer  and  Dodd:  Arch.  Int.  Med.,  Nov.  13,  1913,  p.  488. 

150 


GASTRIC    ANALYSIS  151 

gastric  digestion  and  is  not  limited,  as  in  the  old  method,  to  information 
derived  from  the  analysis  of  a  single  sample  of  stomach  contents  with- 
drawn at  the  end  of  one  hour.  That  the  acid  values  obtained  by  the 
old  method  may  be  grossly  misinterpreted  and  lead  to  an  incorrect 
diagnosis  is  indicated  by  the  foregoing  diagram  (Fig.  45) . 

It  is  set  forth  in  the  above  diagram  that  various  types  of  abnormal 
gastric  secretion  would  be  considered  normal  on  the  basis  of  a  single 
examination  at  the  end  of  one  hour  whereas  the  application  of  the 
fractional  method  reveals  the  abnormality  of  the  secretion  and  enables 
a  rapid  and  correct  diagnosis.  The  removal  of  samples  of  gastric 
contents  at  short  intervals,  for  a  period  of  two  hours  or  more  afte^  a 
test  meal,  is  made  possible  by  the  use  of  a  modified  stomach  tube1  of 
small  diameter  (No.  12  French  tubing)  and  fitted  with  a  metal  tip. 


FIG.  46. — REHFUSS  STOMACH  TUBE. 

The  tip  is  slotted  with  large  perforations,  the  diameter  of  each^being 
equivalent  to  the  maximum  bore  of  the  tubing.  Such  a  tube  can  be 
left  in  the  stomach  through  the  entire  cycle  of  gastric  digestion  without 
inconvenience  to  the  patient.2  A  cut  of  the  Rehfuss  stomach  tube 
(Fig.  46)  is  shown  above.3  Lyon  has  suggested  a  modified  tip.4 

More  recently  Bergeim,5  working  in  the  author's  laboratory, 
has  devised  a  very  useful  apparatus  for  the  determination  of  in- 
tragastric  conductance  and  temperature.  The  apparatus  is  also  provided 
with  an  aspiration  tube  similar  to  that  of  the  Rehfuss  tube  which 
make  possible  the  removal  of  samples  of  gastric  contents  for  chemical 
analysis.  This  apparatus  is  shown  in  Fig.  47,  page  152.  Curves 

1  Rehfuss:  Am.  Jour.  Med.  Sci.t  June,  1914. 

2  McClendon  has  recently  suggested  the  introduction  of  an  electrode  into  the  stomach  in 
an  attempt  to  follow  the  consecutive  changes  in  the  hydrogen  ion  concentration  of  the 
stomach  contents  (see  Am.  Jour.  PhysioL,  38,  180,  1915). 

8  This  tube  is  manufactured  by  Charles  Lentz  &  Sons,  Philadelphia. 
4Lyon:  /.  Am.  Med.  Ass'n.,  74,  246,  1920. 
5  Bergeim:  Amer.  Jour.  PhysioL,  45,  i,  1917 


PHYSIOLOGICAL   CHEMISTRY 


showing   the  relationship  of  conductance  to  acidities  are  given  in 
Fig.  48,  page  152. 

The  idea  of  making  a  fractional  examination  of  gastric  contents  is 
not  new.  Most  of  such  attempts  have  been  made,  however,  by  using 
the  old  type  of  stomach  tube  and  removing  the  entire  stomach  contents 
at  different  intervals  on  successive  days,  e.g.,  after  fifteen  minutes  the 
first  day,  thirty  minutes  the  second  day,  forty-five  minutes  the  third 
day,  etc.  Hayem1  was  the  first  to  employ  this  method  and  later 


FIG.  47.  FIG.  48,. 

FIG.  47. — BERGEIM  INTRAGASTRIC  CONDUCTANCE  APPARATUS. 

Diagrammatic  cross-section  showing  platinum  electrodes  A,  A,  with  leads  A';  thermo- 
couple T  with  leads,  T'\  tube  for  aspiration  B\  and  outer  protecting  tube  C.  (Bergeim: 
American  Journal  of  Physiology,  45,  i,  1917.) 

FIG.  48.— CURVES  SHOWING  RELATIONSHIP  OF  CONDUCTANCE  TO  ACIDITIES. 
\Bergeim:  American  Journal  of  Physiology,  45,  i,  1917. 

Ewald  and  Boas,2  Reichmann,3  v.  Jaksch,4  Kornemann,5  Schule6  and 
Gregersen7  followed  a  similar  procedure.  The  first  report  of  data  from 
the  entire  gastric  cycle  obtained  by  means  of  a  small  bore  tube  were 
made  by  Ehrenreich.8  This  investigator  used  a  Nelaton  catheter. 
Skaller9  has  reported  a  few  experiments  in  which  a  small  bore  stomach 
tube  with  a  metal  tip  was  employed  and  the  stomach  contents 
subjected  to  fractional  analysis. 

1  Hayem:  Brouardel  &  Gilbert's,  Traite  de  Medecine,  4,  236,  1905. 

a Ewald  &  Boas:  Virchow's  Arch.,  101,  325,  1885. 

3 Reichmann:  Zeit.f.  klin.  Med.,  24,  565,  1885. 

4v.  Jaksch:  Zeit.f.  klin.  Med.,  19,  383,  1890. 

'Kornemann:  Arch.  f.  Verdauungskr.,  p.  369,  1912. 

•Schule:  Zeit.f.  klin.  Med.,  27,  461,  1895. 

7  Gregersen:  Arch.  f.  Verdauungskr.,  19,  263,  1913. 

8 Ehrenreich:  Zeit.f.  klin.  Med.,  p.  231,  1912. 

'Skaller:  Berl.  klin.  Woch.,  50,  No.  47,  1913. 


GASTRIC   ANALYSIS 


153 


Until  recent  years,  the  consensus  of  opinion  based  principally  upon 
the  work  of  the  Pawlow  school1  was  to  the  effect  that  the  gastric  juice 
of  normal  man  had  an  average  acid  concentration  of  0.2  per  cent 
hydrochloric  acid,  whereas  the  gastric  juice  of  the  dog  and  cat  had  an 
average  acid  concentration  of  0.4-0.5  per  cent  hydrochloric  acid. 
These  experiments  were  based  principally  upon  the  examination  of 
the  pure  gastric  juice  of  the  lower  animals  as  compared  with  the  stomach 
contents  of  man.  Later  experiments2  have,  however,  demonstrated 
that  the  acid  concentration  of  the  freshly  secreted  gastric  juice  of  man 
is  similar  to  that  of  the  dog,  i.e.,  0.4-0.5  per  cent.  Boldyreff  claims 

a 


§ 


I20minntes 


Diet  :100cx:.oi  0.542  7oHCi  at23°C 

FIG.  49. — INFLUENCE  OF  ACID  INTRODUCED  INTO  THE  NORMAL  HUMAN  STOMACH. 
(Spencer,  Meyer,  Rehfuss  and  Hawk:  American  Journal  of  Physiology,  March,  1916.) 

that  this  initial  high  acidity  of  the  human  gastric  juice  is  normally 
lowered  to  the  "optimum  acidity"  of  0.15-0.2  per  cent  hydrochloric 
acid  by  regurgitation  of  alkaline  fluids  (bile,  pancreatic  and  intestinal 
juices)  from  the  intestine.  This  constitutes  what  Boldyreff  terms 
" the  automatic  regulation  of  gastric  acidity."  This  claim  has  been 


Pawlow : .  The  Work  of  the  Digestive  Glands.    Translated  by  Thompson,  Second  Edition 


1910 


2Babkin:  Die  Aussere  Sekretion  der  Verdauungsdriisen,  Berlin,  1914. 
Boldyreff:  Transactions  of  nth  Congress  of  Physicians, 'St.  Petersburg,  1909. 
Boldyreff:  Quart.  Jour.  Exp.  Physiol.,  8,  i,  1914. 
Carlson:  Am.  Jour.  Physiol. ,  38,  248,  TQI$. 
Bergeim,  Rehfuss  &  Hawk:  Jour.  Biol   Chem.,  19,  345,  1914- 


154 


PHYSIOLOGICAL   CHEMISTRY 


substantiated  by  experiments  made  in  the  author's  laboratory1  and 
elsewhere.2  Both  bile  and  trypsin  are  easily  identified  in  the  stomach 
contents  of  man  after  the  introduction  of  0.5  per  cent  hydrochloric 
acid  into  the  empty  organ.  The  above  points  are  illustrated  by  the 
chart  shown  in  Fig.  49,  page  I53.3 

The  composition  of  human  gastric  juice  and  of  the  residuum  (see 
page  163)  is  given  in  the  following  table: 

COMPOSITION  OF  HUMAN  GASTRIC  JUICE 


Constituent 

Appetite  juice4 

Residuum8 

Specific  gravity 

I    OO7 

i  006 

A  degrees 

—  o  SS 

—  o    An 

Total  acidity  per  cent 

O   45 

O7Q 

Per  100  c.c.  of  Juice 

Total  solids,  gram  .  .               .    . 

o  c<r 

o  08' 

Organic  solids,  gram  . 

O   4-1 

0    <U« 

Inorganic  solids  gram 

O    14. 

o  4<;6 

Total  nitrogen  gram 

o  060 

o  066' 

Total  phosphorus,  gram  

o  .  oo  5  6 

Total  sulphur,  gram  

0.007* 

Ammonia  N,  gram  

0.002-3 

Amino-acid  N,  gram  

o  .  oo  3—  o 

Chlorides  (as  Cl),  gram.... 

o.S 

THE  USE  OF  INDICATORS  IN  DETERMINING  THE  REACTION  OF  GASTRIC 
JUICE  AND  OTHER  FLUIDS 

The  reaction  of  the  gastric  juice  and  other  body  fluids  is  most 
readily  tested  by  means  of  indicators,  so-called  because  they  show 
changes  of  color  with  differing  degrees  of  acidity  or  alkalinity  of  the 
solution.  They  behave  as  though  they  were  weak  acids  or  bases  whose 
ions  and  unionized  molecules  have  different  colors.  Modern  theories 
of  color  in  organic  compounds  however  class  them  as  tautomeric 
substances. 

A  neutral  solution  is  one  in  which  there  are  equal  numbers  of  hy- 

1  Spencer,  Meyer,  Rehfuss  and  Hawk:  Am.  Jour.  PhysioL,  39,  459,  1916. 
2Migai:  Diss.,  St.  Petersburg,  1909. 

MUosorov:  Zent.  PhysioL,  28,  615,  1914. 

Zaitzeff:  Russky  Vrach.,  14,  No.  29,  1915. 
'Spencer  et  al:  LOG.  cit. 
4  Carlson :  LOG.  cit. 

6  Fowler,  Rehfuss  and  Hawk:  LOG.  cit. 
•Fowler  &  Buchanan:  Unpublished. 


GASTRIC   ANALYSIS  155 

drogen  and  hydroxyl  ions.  An  acid  solution  has  a  preponderance  of 
hydrogen  ion  and  an*  alkaline  solution  an  excess  of  hydroxyl  ion.  All 
indicators  do  not  show  changes  of  color  at  the  true  neutral  point,  but 
at  some  fixed  degree  of  acidity  (or  alkalinity),  i.e.,  at  a  definite  hydrogen 
or  hydroxyl  ion  concentration.  Indicators  which  change  color  at  the 
approximate  true  neutral  point  are  litmus  and  rosolic  acid,  while  phenol- 
phthalein  changes  color  in  a  slightly  alkaline  solution.  Congo  red, 
sodium  alizarin  sulphonate  and  tropaeolin  OO  are  examples  of  indicators 
which  change  color  in  an  acid  solution. 

Organic  acids  in  general  are  not  sufficiently  strong;  i.e.,  do  not  dis- 
sociate with  the  production  of  enough  hydrogen  ion  to  cause  color 
changes  in  dilute  solution  with  indicators  of  the  last-mentioned  class. 
Litmus,  rosolic  acid  and  phenolphthalein,  however,  change,  at  so 
low  a  hydrogen  ion  concentration  that  th^y  are  affected  by  dilute 
solutions  of  organic  acids  and  may  be  used  for  their  titration.  Even 
very  dilute  solutions  of  mineral  acids  are  sufficiently  acid  to  produce 
color  changes  with  Congo  red,  alizarin,  etc.,  and  hence  these  indicators 
may  be  used  in  the  titration  of  mineral  acid.  Phenolphthalein  which 
changes  color  in  a  weakly  alkaline  solution  indicates  the  presence  of  acid 
combined  with  weakly  alkaline  substances  (as  protein)  as  well  as  other 
types  of  acid  such  as  acid  salts,  and  hence,  is  used  in  the  titration  of 
solutions  for  their  total  acidity. 

The  hydrogen  ion  concentration  of  pure  water  or  a  neutral  solution 
is  approximately  i  X  jo"7,  being  expressed  as  approximate  moles  of 
hydrogen  ion  per  liter.  That  is,  water  is  a  1/10,000,000  N  solution  of 
hydrogen  ions.  The  concentration  of  hydroxyl  ions  in  pure  water  or  a 
neutral  solution  is  exactly  equal  to  that  of  the  hydrogen  ions,  so  that 
water  may  be  considered  to  be  an  N/ 10,000,000  alkali  as  well  as  an 
N/ 10,000,000  acid.  Hydrogen  ion  concentrations  are  often  ex- 
pressed for  the  sake  of  brevity  as  their  logarithms  with  the  sign  re- 
versed. For  example  the  logarithm  of  i  X  io~~7  would  be  —7.0  and 
according  to  this  notation  the  H  ion  concentration  would  be  expressed 
as  PH  =  7-o.  The  product  of  the  hydrogen  ion  concentration  (H+) 
by  the  hydroxyl  ion  concentration  (OH~)  is  constant  at  about  i  X  io~14 
so  that  as  (H+)  increases  from  i  X  io~7  (PH  =  7.0)  to  i  X  io~~4 
(PH  =  4.0)  the  (OH~)  falls  to  i  X  io~10,  and  vice  versa.  It  must  be 
borne  in  mind  that  higher  figures  for  the  logarithmic  notation  indicate 
lower  figures  for  (H+).  The  hydrogen  ion  concentrations  at  which 
certain  indicators  commonly  used  in  titration  work  change  color,  are 
indicated  below. 


156  PHYSIOLOGICAL   CHEMISTRY 


Indicator 
Phtfnolphthalein.  . 

Hydroge 
Between  i 

n  ion  concentration 

C( 

X  io~8and  i  X  io~9  

rrue  nature 
of  solution 
when  the 
>lor  changes 
Alkaline. 
Neutral. 
Neutral. 
Neutral. 
Acid. 
Acid. 
Acid. 
Acid. 
Acid. 

Neutral  red  

i  X  icr7 

Rosolic  acid  

.  .  .   i  X  io~7  

Litmus  

Between 

X  io~6  and  i  X  io~7.... 
X  io~6  and  i  X  io~6  
X  io~6and  i  X  io~6.  .  .  . 
X  io~3  and  i  X  io~4.  .  .  . 
X  io~2  and  i  X  io~3  

Sodium  alizarin  sulphonate 

Between 

Congo  red 

Between 

Dimethyl-amino-azobenzene 

Between 

Methyl  orange  

Between 

Tropaeolin  OO  .  . 

I   X  I0~2 

Tests  with  Indicators. — Prepare  a  series  of  solutions  of  varying  acidities  as 
outlined  in  the  following  table,  page  157.  Introduce  5  or  10  c.c.  portions  of  each 
of  these  into  a  series  of  test-tubes  and  add  to  each  a  few  drops  of  a  solution  of 
Tropaeolin  OO.  Make  a  note  of  the  colors  produced,  in  the  spaces  left  for  this 
purpose.  In  the  same  way  test  out  the  other  indicators  mentioned,  in  order, 
using  in  each  case  a  few  drops  of  the  indicator  solution.  The  tests  using  the  last 
three  mentioned  indicators:  Giinzberg's,  Boas'  and  Tropaeolin  (evaporation 
test)  are  carried  out  diff erently  as  indicated  below. 

Are  the  following  assumptions,  on  which  the  use  of  certain  of  these 
indicators  in  gastric  analysis  is  based,  borne  out  by  your  findings? 

1.  That  Topfer's  reagent  (Dimethyl-amino-azo-benzene)  gives  its 
characteristic  pinkish-red  color  only  in  the  presence  of  free  HC1. 

2.  That  a  blue  color  with  Congo  red  indicates  free  hydrochloric  (or 
other  mineral  acid),  a  violet  color  indicates  an  organic  acid,  and  a  brown 
color  indicates  combined  hydrochloric  acid. 

3.  That  Tropaeolin  00  and  methyl  orange  are  indicators  for  free 
mineral  acid. 

4.  That  alizarin  reacts  to  free  mineral  acid,  organic  acids  and  acid 
salts  but  not  to  combined  HC1. 

5.  That  phenolphthalein  can  be  used  in  titrating  total  acidity,  that 
is,  acidity  due  to  mineral  and  organic  acids,  acid  salts  and  combined 
acid. 

6.  That  iodine  is  liberated  from  KI— KIOs  to  a  relatively  slight  ex- 
tent by  other  than  free  mineral  acid. 

7.  That  Giinzberg's  test  is  the  most  satisfactory  one  for  free  HC1 
and  that  Boas'  reagent  and  Tropaeolin  OO  are  also  delicate  reagents  for 
free  mineral  acid. 

Special  Tests  for  Free  HC1. — Perform  the  following  tests  on  the  solutions  as 
outlined  above  and  tabulate  the  results. 

i.  Giinzberg's  Reagent.1 — Place  1-2  drops  of  the  reagent  in  a  small  porcelain 
evaporating  dish  and  carefully  evaporate  to  dryness  over  a  low  flame.  Insert 
a  glass  stirring  rod  into  the  mixture  to  be  tested  and  draw  the  moist  end  of  the 

1  Giinzberg's  reagent  is  prepared  by  dissolving  2  grams  of  phloroglucinol  and  i  gram  of 
vanillin  in  100  c.c.  of  QS  per  cent  alcohol. 


GASTRIC  ANALYSIS 


TABULATION  ON  RESULTS  OF  TESTS  ON  INDICATORS 

*°   o   0 
N  |0  §-.2? 

M  8  .g  >  15  1  • 

H  o  ^ 

sium  dihydrogen  phosphate  of  Ms  molecular  strength  (9.078  grams  to  a  Uter  of  water)  and  one  of  disodium  hydrogen  phosphate 
in  the  air  for  a  few  weeks)  NazHPO^HiO  of  similar  strength  (11.876  grams  to  a  liter).  To  prepare  the  acid  phosphate  solution 
ition  of  the  disodium  salt  with  9  parts  of  the  solution  of  the  dihydrogen  phosphate.  For  the  basic  phosphate  solution  the  proper 

epare  a  borate  solution  by  dissolving  12.404  grams  of  pure  boric  acid  (0.2  mol.)  in  100  c.c.  N  NaOH  solution  and  dilute  with 
•NaOH  solution  by  mixing  6  parts  of  the  borate  solution  with  4  parts  of  N/io  NaOH. 
per  cent  HCI  with  a  small  amount  of  Witte's  peptone  and  boil  until  the  solution  no  longer  gives  a  blue  but  only  a  brown  color  with 

olin  OO,  0.05  gram  in  100  c  c.  50  per  cent  alcohol.  Methyl  orange,  o.i  gram  in  100  c.c.  water.  TOpfer's  reagent,  0.5  gram 
.c.  95  per  cent  alcohol.  KI  —  KlOt,  mix  equal  volumes  of  8  per  cent  KlOt  and  48  per  cent  KI  solutions.  Congo  red,  0.5  gram  in  90 
mt  alcohol.  Alizarin,  i  gram  sodium  alizarin  sulphonate  in  100  c.c.  water.  Litmus,  preferably  azo-litmin  I  per  cent  solution  in 
c.c.  95  per  cent  alcohol,  add  50  c.c.  water.  Phenolphthalein,  i  gram  in  100  c.c.  95  per  cent  alcohol. 

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(i)  Make  up  a  solution  of  potas 
(obtained  by  drying  the  ordinary  sail 
used  in  the  test  mix  i  part  of  the  soli 
tions  are  20:  I. 
(2)  Borate-NaOH  solution.  Pr 
water  to  a  liter.  Prepare  the  Borate 
(3)  Combined  HCI.  Treat  0.04 
Congo  red  paper. 
(4)  Indicator  solutions.  Tropat 
dimethyl-amino-azo-benzene  in  100  c 
c.c.  water  and  add  10  c.c.  95  per  c< 
water.  Neutral  red,  0.05  gram  in  50 

Solution 

2.  0.04  per  cent  HCI  

3.  0.6  per  cent  acetic  acid  

4.0.04  per  cent  combined  HC1(3) 

• 

• 

5.  Acid  phosphate  i  :  9(1)  •  •  •  • 

i 

$ 

<o 

7.  Basic  phosphate  20:1(1). 

8.  Borate-NaOH6:4(2)  

9.  NaOH  0.4  per  cent  

158  PHYSIOLOGICAL  CHEMISTRY 

rod  through  the  dried  reagent.  Warm  again  gently  and  note  the  production  of  a 
purplish-red  color  in  the  presence  of  free  hydrochloric  acid. 

2.  Boas'  Reagent.1 — Perform  this  test  in  the  same  manner  as  i,  above. 
Free  hydrochloric  acid  is  indicated  by  the  production  of  a  rose-red  color  which 
becomes  less  pronounced  on  cooling. 

3.  Tropaeolin  OO,2 

(C6H5)NH-C6H4-N  =  N-C6H4-S03Na. 

Place  2  drops  of  the  solution  to  be  tested  and  i  drop  of  the  indicator  in  an  evapo- 
rating dish  and  evaporate  to  dryness  over  a  low  flame.  The  formation  of  a  red- 
dish-violet color  indicates  free  hydrochloric  acid. 

This  test  may  also  be  conducted  in  the  same  manner  as  i,  above. 

HYDROGEN  ION  CONCENTRATION  AND  TITRATABLE  ACIDITY 

The  acidity  of  a  solution  may  be  determined  in  two  different  ways 
by  means  of  indicators.  One  method  is  by  titration  with  standard 
alkali  using  the  indicator  to  determine  the  end  point  of  the  titration. 
For  this  purpose  the  indicator  should  be  one  which  gives  a  sharp  color 
change  which  is  sensitive  to  the  form  of  acidity  which  is  to  be  deter- 
mined, and  which  is  not  destroyed  by  any  substance  contained  in  the 
titration  mixture.  Thus  phenolphthalein  can  be  used  for  the  titration 
of  strong  bases  and  nearly  all  weak  acids,  but  cannot  be  used  for  weak 
bases,  and  is  unsatisfactory  in  the  presence  of  ammonium  salts.  Methyl 
orange  on  the  other  hand  is  useful  for  strong  acids  and  weak  bases  such 
as  ammonia  and  for  the  soluble  carbonates  but  cannot  be  used  for  weak 
acids  such  as  carbonic  acid  or  the  organic  acids.  Almost  any  indicator 
may  be  used  in  the  titration  of  mineral  acids  against  strong  bases  such 
as  KOH  inasmuch  as  under  these  conditions  I  drop  of  the  standard 
solution  will  throw  the  hydrogen  ion  concentration  so  far  beyond  that  of 
neutrality  that  the  turning  point  of  any  common  indicator  will  be 
passed. 

Titration  does  not,  however,  enable  us  to  determine  in. all  cases  the 
true  acidity  of  a  solution,  that  is,  its  hydrogen  ion  concentration.  In  the 
case  of  strong  acids  and  bases  very  accurate  results  for  the  true  acidity 
may  be  obtained  in  this  way.  In  the  case  of  weak  acids  or  bases  the 
titration  values  may  give  but  slight  information  as  to  the  true  acidity. 
Thus  in  the  case  of  a  slightly  dissociated  acid,  such  as  acetic  acid,  as 
fast  as  the  acidity  due  to  its  dissociated  hydrogen  ions  is  neutralized 
the  undissociated  acid  ionizes  further  and  the  titration  value  finally 
obtained  represents  the  total  acid  present  at  the  beginning  both  ionized 
and  unionized.  Salts  of  strong  acids  and  very  weak  bases  and  vice 

1  Boas'  reagent  is  prepared  by  dissolving  5  grams  of  resorcinol  and  3  grams  of  sucrose  in 
100  c.c.  of  50  per  cent  alcohol. 

2  Prepared  by  dissolving  0.05  gram  of  tropaeolin  OO  in  100  c.c.  of  50  per  cent  alcohol. 


GASTRIC  ANALYSIS  159 

versa  also  hydrolyze  during  the  course  of  the  titration  and  the  values 
obtained  in  no  sense  represent  the  true  acidity. 

Hydrogen  ion  concentrations  may  be  determined  through  a  certain 
range  by  means  of  indicators.1  The  unknown  solution  is  treated  with 
a  few  drops  of  indicator  and  the  color  obtained  compared  with  that 
produced  with  the  same  amount  of  indicator  and  a  solution  of  known 
hydrogen  ion  concentration.  If  the  same  tint  is  produced  in  both 
cases  the  two  acidities  are  the  same.  This  is  of  course  only  true  when 
the  indicator  chosen  is  a  suitable  one,  that  is,  one  that  shows  definite 
color  changes  in  hydrogen  ion  concentrations  in  the  neighborhood  of 
that  of  the  unknown.  The  choice  of  indicators  for  this  purpose  is 
somewhat  different  than  that  for  titration  purposes.  For  use  in  the 
determination  of  the  hydrogen  ion  concentration  of  a  solution  we  need 
an  indicator  showing  a  very  gradual  change  in  color  through  a  given 
range,  one  which  is  not  readily  affected  by  the"presence  of  neutral  salts 
or  other  substances  likely  to  be  present,  and  the  color  of  which  does 
not  fade  too  rapidly.  The  ranges  through  which  a  number  of  indicators 
may  be  used  with  satisfactory  results  for  the  determination  of  hydrogen 
ion  concentrations  is  indicated  in  the  chart  (Fig.  50,  page  160).  Those 
surrounded  by  the  heavy  lines  are  the  most  satisfactory. 

The  chart  also  indicates  how  standard  solutions  of  definite  hydrogen 
ion  concentrations  may  be  made  up  from  a  series  of  stock  solutions, 
by  mixing  in  various  proportions.  The  stock  solutions  indicated  on  the 
chart  were  suggested  by  Sorensen  and  are  as  follows:  o.io  N  HC1; 
o.io  N  NaOH;  7.505  g.  glycocoll  plus  5.85  gm.  NaCl  per  liter;  11.876 
g.  Na2HPO4.2H2O  per.  liter;  9.078  g.  KH2PO4  per  liter;  21.008  g. 
citric  acid  in  i  liter  of  0.20  N  NaOH;  12.404  g.  boric  acid  in  i  liter  of 
o.io  N  NaOH.  The  other  solutions  are  0.20  N  sodium  acetate  and 
0.20  N  acetic  acid.  Solutions  of  known  hydrogen  ion  concentration  are 
prepared  from  these  by  mixing  in  the  proportions  indicated  on  the 
chart,  the  abscissae  representing  parts  of  the  more  alkaline  or  less  acid 
constituent.  Thus  a  mixture  of  seven  volumes  of  the  sodium  acetate 
stock  solution  with  three  volumes  of  the  stock  acetic  acid  solution 
gives  a  mixture  with  an  hydrogen  ion  concentration  of  i  X  io~6 
(exponent:  5.0).  The  mixtures  are  most  satisfactory  through  the 
ranges  where  the  hydrogen  ion  concentration  changes  most  gradually, 
that  is,  through  the  flatter  portions  of  the  curves. 

The  amounts  of  indicator  solutions  and  their  strengths  to  be  used 
in  the  determinations  of  hydrogen  ion  concentrations  in  10  c.c.  portions 
of  unknown  solution  are  indicated  below. 

*For  a  discussion  of  colorimetric  and  electrometric  methods  and  review  of  the  literature 
see  Clark:  The  Determination  of  Hydrogen  Ions,  Baltimore,  1920. 


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PHYSIOLOGICAL   CHEMISTRY 


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GASTRIC  ANALYSIS 


161 


1.  Alizarin' yellow  R  (p- 
nitrobenzene-azo-sali- 
cylic  acid) 

2.  Azolitmin  (litmus) 

3.  Cochineal 

4.  a,  5-dinitro-hydroqumol 

5.  Mauvein 

6.  Methyl  orange 

7.  Methyl  red 

8.  Methyl  violet 

9.  Neutral  red 

10.  p-Nitrophenol 

11.  Phenolphthalein 

12.  Rosolic  acid 

13.  Thymolphthalein 

14.  Tropaeolin  O 

15.  Tropaeolin  OO 

1 6.  Tropaeolin  OOO 


INDICATOR  SOLUTIONS 

Drops  Preparation  of  solution 


10-5  o.  i  gram  to  1000  c.c.  water. 

Aqueous  solution. 
Alcoholic  solution. 

5-2  i    gram  to  1000  c.c.  alcohol. 

8-1  0.5  gram  to  1000  c.c.  water. 

5-3  o.i    gram    recrystallized    salt    to    1000    c.c. 

water. 

4-2  Saturated  solution  in  50  per  cent  alcohol. 

8-1  0.5  gram  to  1000  c.c.  water. 

20-10          o .  i  gram  in  500  c.c.  alcohol,  and  500  c.c.  water. 
20-3  0.4  gram  to  60  c.c.  alcohol,  940  c.c.  water. 

20-3  0.5  gram  to  500  c.c.  alcohol,  500  c.c.  water. 

15-6  0.4  gram  to  400  c.c.  alcohol,  6co  c.c.  water. 

10-3  0.4  gram  to  500  c.c.  alcohol,  500  c.c.  water. 

10-5  o.  i  gram  to  1000  c.c.  water. 

5-3  Of  recrystallized  salt,  o.i  gram  to  1000  c.c. 

water.          > 
10-4  o .  i  gram  to  1000  c.c.  water. 


Determination  of  Hydrogen  Ion  Concentration. — Introduce  10  c.c.  portions 
of  the  unknown  solution  into  a  series  of  test-tubes  of  similar  diameter  and  of 
clear  glass.  Test  first  with  litmus  paper  which  changes  at  about  the  neutral 
point.  According  to  whether  the  reaction  is  acid  or  basic  to  litmus  test  other  indi- 
cators on  the  acid  side  such  as  p-nitrophenol,  methyl  orange  and  tropseolin  OO, 
or  on  the  basic  side  as  phenolphthalein.  Select  an  indicator  which  gives  with  the 
solution  neither  its  maximum  acid  or  maximum  basic  color.  Note  from  the  chart 
through  what  range  this  indicator  exhibits -its  characteristic  change  of  color. 
Then  to  10  c.c.  portions  of  standard  solutions  of  known  hydrogen  ion  concentra- 
tion (furnished  by  the  instructor),  which  cover  approximately  the  same  range  as 
the  indicator  add  exactly  the  same  number  of  drops  of  indicator  solution  as  was 
added  to  the  standard.  Compare  colors  of  unknown  and  standards  until  one  is 
found  which  matches  and  which  consequently  possesses  the  same  hydrogen  ion 
concentration.  If  the  unknown  is  so  strongly  acid  or  basic  that  none  of  the  indi- 
cators mentioned  can  be  used  directly  it  will  be  necessary  to  dilute  it  with  10  or  a 
greater  number  of  volumes  of  water  before  testing  further. 

In  case  the  unknown  solution  is  slightly  colored  the  standards  should  like- 
wise be  brought  to  the  same  tint  by  the  addition  of  some  coloring  agent  as  Bis- 
marck brown,  methyl  orange,  methyl  violet,  etc.,  before  making  the  comparison. 

For  applications  of  the  indicator  method  for  the  determination  of  hydrogen  ion 
concentration  to  biological  fluids  see  chapters  on  the  quantitative  analysis  of 
blood  (XVI)  and  urine  (XXVII). 

Comparison  of  H  Ion  Concentration  and  Titratable  Acidity. — i.  Determine 
colorimetrically  the  H  ion  concentration  of  an  N/ioo  solution  of  hydrochloric  acid 
using  tropaeolin  OO  as  an  indicator  and  of  an  N/ioo  acetic  acid  using  methyl 
orange  as  an  indicator.  Note  the  great  difference  between  the  true  acidities  of 
the  two  solutions. 

Titrate  10  c.c.  portions  of  N/ioo  hydrochloric  acid  and  of  N/ioo  acetic  acid 
with  N/ioo  KOH  Using  phenolphthalein  as  an  indicator.  Note  that  identical 
results  are  obtained  for  the  titratable  acidities  of  the  two. 

2.  Determine  colorimetrically  the  H  ion  concentration  of  an  N/ioo  KOH 


1 62  PHYSIOLOGICAL   CHEMISTRY 

solution  using  tropaeolin  O  as  an  indicator,  and  of  an  N/ioo  ammonia  solution 
using  phenolphthalein  as  an  indicator.  Note  the  results  and  then  titrate  10  c.c. 
portions  of  both  solutions  with  N/ioo  HC1  using  alizarin  as  an  indicator. 

3.  Mix  equal  portions  of  M/i5  potassium  dihydrogen  phosphate  and  M/i$ 
disodium  phosphate  (see  chart).    Note  that  the  mixture  is  practically  neutral  to 
litmus.    Titrate  one  10  c.c.  portion  of  this  mixture  with  N/io  KOH,  using  phe- 
nolphthalein as  an  indicator.    Titrate  another  portion  with  N/io  HC1  solution, 
using  methyl  orange  as  an  indicator. 

4.  Mix  equal  volumes  of  N/5  sodium  acetate  solution  and  N/5  acetic  acid. 
Note  that  the  mixture  is  acid  to  litmus.    Titrate  one  10  c.c.  portion  with  N/io 
HC1  using  tropaeolin  OO  as  an  indicator.    Titrate  another  portion  with  N/io 
KOH  using  phenolphthalein  as  an  indicator. 

THE  FRACTIONAL  METHOD  OF  GASTRIC  ANALYSIS 

Procedure  in  Gastric  Analysis  by  the  Fractional  Method 

1.  Introduction  of  the  stomach  tube  (see  pages  162  and  163). 

2.  Removal  of  the  residuum  (see  pages  163  and  164). 

3.  Feeding  the  test  meal  (see  page  164). 

4.  Feeding  the  retention  meal  (in  special  cases),  see  page  164. 

5.  Removing  samples  of  stomach  contents  for  analysis  (see  page  164) . 

6.  Examination  of  the  samples  for: 

(a)  Total  acidity  (see  page  161). 

(b)  Free  acidity  (see  page  167). 

(c)  Pepsin  (see  page  168). 

(d)  Trypsin  (not  a  routine  procedure),  see  page  171. 

(e)  Lactic  acid  (see  page  172). 
(f)'  Occult  blood  (see  page  173). 
(g)  Bile  (see  page  174). 

(H)  Microscopical  constituents  (see  page  175). 

i.  Introduction  of  the  Stomach  Tube. — Whereas  the  large  tube  is 
directly  inserted  by  propulsion,  the  Rehfuss  tube  is  swallowed  in  the 
natural  manner  and  aided  by  gravity.  The  tube  may  be  passed  in  one 
of  three  ways,  i.e. :  (i)  lubricated;  (2)  with  aid  of  fluid;  (3)  after  throat  is 
cocainized.  When  passed  by  the  first  method  the  tip  of  the  tube,  after 
thorough  lubrication  with  glycerol  or  liquid  petrolatum,  is  seized  between 
the  thumb -and  forefinger  and  placed  on  the  tongue.  Then  with  the 
aid  of  the  forefinger  the  tip  is  pushed  backward  until  it  reaches  the  root 
of  the  tongue  and  is  engaged  in  the  oropharynx.  Then  the  patient  is 
encouraged  to  swallow  persistently  while  the  tube  is  slowly  fed  into  the 
mouth.  After  slight  discomfort  in  the  pharynx  and  its  passage  past  the 
level  of  the  cricoid  cartilage,  practically  no  discomfort  is  felt.  This 


GASTRIC   ANALYSIS  163 

method  is  used  when  it  is  essential  that  the  pure  gastric  secretion  or 
residuum  be  obtained.  Ordinarily,  however,  it  is  much  easier  to  swallow 
the  tube  by  the  second  method.  This  method  consists  in  placing 
the  tip  in  the  oropharynx  and  then  giving  the  patient  a  measured 
quantity  of  water  or  tea  to  swallow.  The  movements  induced  by  the 
swallowing  carry  the  tube  rapidly  to  the  stomach  with  a  minimum  of 
discomfort.  When  an  Ewald  meal  (see  below)  is  given,  part  of  the  tea 
can  be  reserved  for  swallowing  the  tube.  This  procedure  makes  it 
scarcely  more  arduous  than  the  swallowing  of  food.  Should  the  patient, 
however,  be  extremely  neurotic  or  the  unfortunate  possessor  of  marked 
pharyngeal  hyperesthesia,  cocain  hydrochloride  in  2  per  cent  aqueous 
solution  can  be  applied  to  the  throat  rendering  the  passage  of  the  tube 
practically  insensitive.  When  the  tube  has  entered  the  stomach,  as- 
piration of  the  material  shows  the  characteristic  gastric  contents. 
Should  the  tip  remain  in  the  esophagus  through  transient  cardiospasm 
or  other  cause,  aspiration  results  in  the  removal  of  only  a  very  small 
specimen  having  all  the  characteristics  of  the  pharyngeal  and  esopha- 
geal  secretions. 

2.  Removal  of  Residuum. — If  the  so-called  "empty"  stomach  is 
examined  in  the  morning  before  any  food  or  drink  has  been  taken  it 
will  be  found  to  contain  considerable  material.  This  is  termed  re- 
siduum. Before  a  test  meal  is  introduced  into  the  stomach,  this  organ 
should  be  emptied.  If  this  is  not  done' we  cannot  consider  the  samples 
withdrawn  after  the  test  meal  is  eaten  as  representing  the  secretory 
activity  of  the  gastric  cells  under  the  influence  of  the  stimulation  of  the 
test  meal.  It  has  been  generally  recognized,  clinically,  that  a  residuum 
above  20  c.c.  is  pathological.1  Such  a  volume  has  been  considered  as 
indicative  of  hypersecretion,  and  this  in  turn  in  many  cases  indicates  an 
organic  lesion.  The  observations  indicating  that  a  residuum  of  over 
20  c.c.  was  pathological,  were  made  upon  residuums  removed  by  means 
of  the  old  type  of  stomach  tube  which  does  not  completely  empty  the 
stomach.2  When  the  residuum  is  completely  removed  by  means  of 
the  Rehfuss  tube  it  has  been  demonstrated  that  the  normal  residuum 
is  practically  always  over  20  c.c.  and  that  the  average  is  about  50  c.c. 
for  both  men3  and  women.4  The  normal  residuum  has  been  found  to 
possess  all  the  qualities  of  a  physiologically  active  gastric  juice  with 

1Loeper:  Lemons  de  pathologie  digestive,  1912,  Series  2,  pp.  17-19. 

Zweig:  Magen-  und  Darmkrankheiten,  p.  459. 

Kemp:  Diseases  of  the  Stomach,  Intestines  and  Pancreas,  1912,  p.  133. 

Wolff:  Taschenbuch  der  Magen-  und  Darmkrankheiten,  p.  22. 
'Harmer  and  Doddt  Loc.  cit. 
3  Rehfuss,  Bergeim  and  Hawk:  Jour.  Am.  Med.  Ass'n,  63,  n,  1914. 

Fowler,  Rehfuss  and  Hawk:  Jour.  Am.  Med.  Ass'n,  65,  1021,  1915. 
4 Fowler  and  Zentmire:  Jour.  Am.  Med.  Ass'n,  68,  167,  1917. 


164  PHYSIOLOGICAL   CHEMISTRY 

an  average  total  acidity  of  30  and  an  average  free  acidity  of  18.5. 
The  residuum  is  often  colored  by  bile.  This  is  particularly  true  if 
the  fluid  has  a  relatively  high  acidity.  Trypsin  is  also  generally  present. 
These  findings  indicate  regurgitation  (see  page  171).  Pathological 
residuums  may  contain  blood,  pus,  mucus  and  may  show  food  retention 
which  is  indicative  of  disturbed  food  evacuation.  The  quantity 
may  also  be  much  increased  due  to  hypersecretion.  A  residuum  of 
large  volume  possessing  a  total  acidity  value  of  70  or  over  may  indicate 
ulcer. 

Analysis  of  Residuum. — Remove  the  residuum  as  directed  under  (5),  below, 
and  analyze  the  fluid  according  to  methods  outlined  on  page  165. 

3.  The  Test  Meal. — Before  making  an  analysis  of  the  stomach 
contents  it  is  customary  to  introduce  something  into  the  stomach  which 
will  stimulate  the  gastric  cells.     The  response  to  this  stimulation  is 
then  measured  clinically  by  the  determination  of  total  acidity,  free 
acidity  and  pepsin  in  the  stomach  contents.     Many  forms  of  test  meal 
have  been  used. 

The  test  meal  most  widely  employed  is  the  Ewald  test  meal.  This  consists 
of  2  pieces  (35  grams)  of  toast  and  8  ounces  (250  c.c.)  of  tea. 

Inasmuch  as  it  was  demonstrated  in  the  author's  laboratory1  that 
water  gave  a  similar  gastric  stimulation  to  that  produced  by  the  Ewald 
meal  it  was  suggested  that  a  simple  water  meal  might  be  substituted 
for  the  Ewald  meal.  This  water  meal  also  has  the  added  advantage 
of  enabling  one  to  determine  the  presence  of  food  rests  and  to  test  more 
accurately  for  lactic  acid,  blood  and  bile. 

4.  The  Retention  Meal. — In   order  to  obtain  more  information 
regarding  gastric  motility  than  is  furnished  by  the  ordinary  test  meal 
described  above  the  patient  may  be  fed  a  so-called  retention  meal.     This 
meal  is  fed  in  place  of  the  regular  evening  meal  and  contains  substances 
readily  detected.     In  the  morning  before  breakfast  (7-8  a.  m.)  remove 
the  stomach  contents  (residuum,  see  page  163)  by  aspiration  and  examine 
for  food  rests.     The  normal  stomach  should  give  no  evidences  of  food 
retention.     A  satisfactory  retention  meal  consists  of  4  ounces  each  of 
boiled  string  beans  and  rice.2    Diets  containing  prunes,  raspberry  mar- 
malade, lyeopodium  powder,  etc.,  have  also  been  employed.     In  many 
instances  an  ordinary  mixed  diet  will  serve  the  purpose. 

5.  Removal  of  Samples  for  Analysis.- — At  intervals  of  exactly  15 
minutes  from  the  time  the  test  meal  is  eaten  until  the  stomach  is  empty 

^ergeim,  Rehfuss,  and  Hawk:  Jour.  Biol.  Chem.,  19,  345,  1914. 

Rehfuss,  Bergeim  and  Hawk:  Jour.  Am.  Med.  Ass'n,  63,  n,  1914. 
8  Myers  and  Fine:  Essentials  of  Pathological  Chemistry,  1913. 


GASTRIC  ANALYSIS  165 

5-6  c.c.  samples  of  gastric  contents  are  withdrawn  from  the  stomach 
by  means,  of  aspiration. 

In  the  removal  of  samples  from  the  stomach,  it  is  essential  that  very 
little  traction  be  employed.  To  completely  empty  the  stomach,  aspira- 
tion is  practised  in  four  positions:  (a)  on  the  back;  (b)  on  the  stomach; 
(c)  on  right  side,  (d)  on  left  side.  This  results  in  complete  evacuation 
of  the  stomach.  Three  tests  may  be  employed  to  determine  whether 
the  stomach  is  empty:  (i)  No  more  material  can  be  aspirated  in  any 
position;  (2)  injection  of  air  and  auscultation  over  the  stomach  with  a 
stethoscope  reveals  a  sticky  rale  and  not  a  series  of  gurgling  rales 
such  as  is  heard  when  there  is  material  in  the  stomach;  (3)  lavage  or 
irrigation  through  the  tube  which  shows  the  absence  of  all  food  in  the 
stomach. 

6.  Examination  of  the  Samples. — The  old^nethods  of  gastric  analy- 
sis involved  the  collection  (by  analysis  and  calculation)  of  data  regard- 
ing several  types  of  acidity  (see  Topfer's  method,  page  176).  The 
modern  tendency  among  clinicians  is  to  lay  particular  emphasis  upon 
the  values  for  total  acidity  and  free  acidity.  The  determination  of  the 
peptic  activity  is  also  important  as  well  as  the  demonstration  of  the 
presence  or  absence  of  occult  blood,  lactic  acid,  mucus,  food  rests,  etc. 

Procedure. — Strain  each  sample  through  a  fine-mesh  cheese  cloth. 1  Examine 
the  residue  for  mucus,  blood2  and  food  rests.  Use  the  strained  stomach  contents 
for  the  determination  of  total  acidity,  free  acidity  and  peptic  activity  by  methods 
which  follow. 

(a)  Determination  of  Total  Acidity.— Principle. — The  indicator 
used  is  phenolphthalein.  Since  the  indicator  reacts  with  mineral 
acid,  organic  acid,  combined  acid  and  acid  salts  the  values  obtained 
represent  the  total  acidity  of  the  solution. 

Procedure. — Measure  i  c.c.  of  the  strained  stomach  contents  by  means  of  an 
Ostwald  pipette  and  introduce  it  into  a  low-form  60  c.c.  porcelain  evaporating 
dish.  Dilute  with  15  c.c.  of  distilled  water.  Add  2  drops  of  a  i  per  cent  alcoholic 
solution  of  phenolphthalein  and  titrate  with  N/ioo  sodium  hydroxide  until  a 
faint  pink  color  is  obtained  and  persists  for  about  two  minutes.3  Take  the  burette 
reading  and  calculate  the  total  acidity. 

*The  examination  for  microscopical  constituents  (see  (h)  p.  175)  should  be  made  on  the 
original  (unstrained)  gastric  contents.  Tests  for  occult  blood  may  be  made  on  the  sedi- 
ment if  desired. 

2  The  detection  of  blood  is  rather  more  satisfactory  in  the  residue  than  in  the  strained 
fluid. 

3  Procedure  for  Serial  Titrations. — When  a  series  of  titrations  are  to  be  made  the  following 
procedure  may  be  used:  Arrange  the  numbered  evaporating  dishes  in  rows  on  a  tray.    In- 
troduce i  c.c.  of  the  proper  sample  into  each  dish,  dilute  with  10  c.c.  of  water  and  add  the 
indicator.    Add  the  N/iob  NaOH  to  contents  of  dish  No.  i  at  a  definite  rate  until  a  point  is 
reached  at  which  a  faint  pink  color  is  obtained,  as  described  above.    Return  dish  No.  i  to 
its  place  in  the  tray  and  place  dish  No.  2  under  the  burette.    Take  the  burette  reading  of 
No.  i.     Then'titrate  No.  2  in  the  same  way.     Continue  the  series.     This  procedure  has  the 
advantage  of  being  speedy  and  accurate.     There  is  a  slight  error  made  by  the  rapid  addition 
of  the  NaOH  but  it  is  uniform  and  the  results  (titrations)  are  therefore  comparable. 


1 66 


PHYSIOLOGICAL  CHEMISTRY 


Calculation. — Note  the  number  of  cubic  centimeters  of  N/ioo  NaOH  required 
to  neutralize  i  c.c.  of  stomach  contents,  and  multiply  it  by  10  to  obtain  the  number 
of  cubic  centimeters  N/io  NaOH  necessary  to  neutralize  100  c.c.  of  stomach 
contents.  This  is  the  method  of  calculation  most  widely  used.  For  other  forms 
of  expressing  total  acidity  see  page  177.  Plot  your  results  in  a  form  similar  to 
those  shown  in  Figs.  51  and  52. 

Curves  Obtained  by  the  Fractional  Method. — When  an  Ewald  test  meal 
is  given  to  normal  individuals  a  curve  such  as  indicated  below  is  usu- 
ally obtained.  The  curve  may  vary  within  certain  limits  depending  on 
individual  idiosyncrasies,  but  is  usually  found  to  follow  the  curve 
depicted,  and  the  meal  normally  leaves  the  stomach  in  two  and  one- 


100 


60 


60 


40 


20 


total  ac 
free  ac.1 


20  40  60  80  100  120    minutes 

FIG.  51. — ACIDITY  CURVES  OF  NORMAL  HUMAN  STOMACH. 

half  hours.  Pathologically  every  variation  occurs,  both  in  time  of 
evacuation  as  well  as  the  character  of  the  curve  and  the  quantity  of  the 
secretion  elaborated.  Fig.  45  represents  some  of  the  possibilities  of 
pathological  cases,  but  a  consideration  of  their  interpretation  is  outside 
the  purpose  of  the  present  volume.  It  will  be  evident,  however,  from 
a  consideration  of  the  figure  that  the  cycle  of  gastric  digestion  is  a  con- 
stantly changing  one,  and  no  information  concerning  the  trend  of 
digestion  can  be  obtained  by  an  examination  of  only  a  single  stage  of 
digestion.  Marked  changes  may  precede  or  follow  that  stage  and  the 
possibilities  suggested  in  Fig.  45  are  all  observed  clinically  and  are  of 
varying  significance.  Typical  curves  from  cases  of  hyperacidity, 
gastric  carcinoma  and  achylia  are  shown  in  Figs.  52,  53  and  54 
respectively. 


GASTRIC   ANALYSIS 


167 


(b)  Determination  of  Free  Acidity. — The  reagent  most  widely  used 
clinically,  for  the  determination  of  free  hydrochloric  acid  in  stomach 

100 

acidity 


O 
« 


40 


Freeaciditg 


V*      y*     */4     I      I1/*    IVz    1 V4    2  hours 

FIG.  52. — ACIDITY  CURVES  FROM  A  CASE  OF  HYPERACIDITY. 

contents  is  Topf  er 's  reagent  (see  page  176).    It  has  been  found,  however, 
that  this  reagent  gives  rather  inaccurate  results  due  to  the  uncertain 


1 

1120 
960 
800  y 

0 

640o 

(0 

480^2 

on/%  or» 

/ 

/ 

Ga. 
Cat 

sfr/'c 
cinon. 

a 

i 

/ 
/ 

$i 

/ 

i 

/ 
/ 

/ 
/ 

«XU  00 

60 

s 

s 
/' 

^ 

^Jot 

alac 

16040 

—' 

s 
'^^^ 

^^' 

,^ 

,_—  — 

Fre 

•ac 

FIG.  53. — ACIDITY  AND  PROTEIN  CURVES  IN  GASTRIC  CARCINOMA.    (Clarke  and  Rehfuss: 
Jour.  Am.  Med.  ^4w'«,  64,  1737,  1915.) 

end  point.     For  this  reason  we  have  employed  Sahli's  reagent.1    This 
reagent  contains  KI  and  KIOs  and  liberates  iodine  in  the  presence  of 

1 A  mixture  of  equal  parts  of  a  48  per  cent  solution  of  potassium  iodide  and  an  8  per  cent 
solution  of  potassium  iodate. 


1 68 


PHYSIOLOGICAL   CHEMISTRY 


free  hydrochloric  acid.  The  liberated  iodine  is  titrated  by  thiosulphate 
using  starch  as  an  indicator.  It  gives  values  similar  to  Topfer's  re- 
agent in  average  acidities.1  Acidities  other  than  free  hydrochloric  re- 
act to  a  certain  extent  with  Sahli's  reagent,  so  that,  for  example, 
high  results  are  obtained  after  the  ingestion  of  acid  fruits. 

Procedure. — Measure  i  c.c.  of  the  strained  stomach  contents  by  means  of  an 
Ostwald  pipette  and  introduce  it  into  a  60  c.c.  porcelain  evaporating  dish.  Dilute 
with  10  c.c.  of  distilled  water,  and  add  i  c.c.  of  Sahli's  reagent  (a  mixture  of 
equal  parts  of  48  per  cent  KI  and  8  per  cent  KIO3).  Allow  the  stomach  contents 
thus  treated  to  stand  for  five  minutes  and  then  titrate  with  N/ioo  sodium  thio- 
sulphate until  only  a  faint  yellow  color  remains.  Now  add  5-10  drops  of  a  i 
per  cent  solution  of  soluble  starch  and  continue  the  titration  until  the  blue  color 
disappears.  In  serial  titrations  the  same  procedure  may  be  employed  as  de- 
scribed on  page  165,  note  3. 

Calculation. — Note  the  number  of  cubic  centimeters  of  N/ioo  sodium  thio- 
sulphate required  to  titrate  i  c.c.  of  stomach  contents  to  the  total  disappearance 
of  blue  color  in  the  presence  of  starch.  Inasmuch  as  N/ioo  thiosulphate  is 
equivalent  to  N/ioo  alkali,  this  value  indicates  the  number  of  cubic  centimeters 
of  N/ioo  sodium  hydroxide  necessary  to  neutralize  the  free  hydrochloric  acid  in 


"3  <£o 

80 

40 

£ 

^i* 



^---—  J 

HOURS 

y* 

V2 

3/4         1 

i    r/4 

1% 

FIG.  54.  —  TOTAL  ACIDITY  AND  PROTEIN  CURVES  IN  BENIGN  ACHYLIA  (SOLID  LINE 
REPRESENTS  ACIDITY).     (Clarke  and  Rehfuss:  Jour.  Am.  Med.  Ass'n,  64,  1737,  1915.) 

i  c.c.  of  the  stomach  contents.  Multiply  the  value  by  10  to  obtain  the  number  of 
cubic  centimeters  of  N/io  NaOH  necessary  to  neutralize  100  c.c.  of  stomach 
contents.  This  is  the  method  of  calculation  most  widely  used.  For  other  forms 
of  expressing  free  acidity  see  page  177.  Plot  your  results  in  a  curve  similar 
to  those  shown  in  Figs.  49,  51,  and  52,  pages  153,  166  and  167. 

(c)  Determination  of  Peptic  Activity.  —  (i)  Method  of  Mett2  as 
Modified  by  Nirenstein  and  Schiff.3—  Principle.  —  Small  glass  tubes 
filled  with  coagulated  egg  albumin  are  introduced  into  the  solution  to 
be  tested,  and  kept  for  a  definite  length  of  time  in  the  incubator.  The 
protein  column  is  digested  at  both  ends  of  the  tube  to  an  extent  depend- 
ing upon  the  amount  of  pepsin  present.  The  method  is  not  strictly 
accurate  but  is  the  most  satisfactory  for  clinical  purposes  on  account 
of  its  simplicity.  Nirenstein  and  Schiff  showed  that  human  gastric 


,  Bergeim  and  Hawk:  Unpublished  data. 
2  Mett:  Arch.f.  Anat.  u.  Physiol.,  Verda  1894,  68. 
'Nirenstein  and  Schiff:  Arch.f.  ankheruungsitekn,  8,  559,  1902. 


GASTRIC   ANALYSIS  169 

juice  contained  inhibiting  substances  the  effect  of  which  is  overcome  by 
the  dilution  recommended. 

Procedure. — Introduce  into  a  small  Erlenmeyer  flask  i  c.c.  of  gastric  juice 
and  15  c.c.  of  N/2O  HC1  (=  0.18  per  cent  HC1).  Add  two  Mett  tubes  prepared 
as  indicated  below,  stopper  the  flask  to  prevent  evaporation  and  place  in  an  in- 
cubator at  37°C.  for  24  hours.  By  means  of  a  low  power  microscope  and  a  milli- 
meter scale  (graduated  to  half' millimeters)  determine  accurately  the  length  of 
the  column  of  albumin  digested  at  each  end  of  the  tubes.  It  is  well  to  run  the 
determination  hi  duplicate  in  which  case  the  result  is  the  average  of  the  eight 
figures  obtained.  Ordinarily  from  2-4  mm.  of  albumin  are  digested  by  normal 
human  gastric  juice. 

Calculation. — The  peptic  power  is  expressed  as  the  square  of  the  number  of 
millimeters  of  albumin  digested.  This  is  based  on  the  Schutz-Borissow  law  that 
the  amount  of  proteolytic  enzyme  present  in  a  digestion  mixture  is  proportional 
to  the  square  of  the  number  of  millimeters  of  albumin  digested.  Therefore  a 
gastric  juice  which  digests  2  mm.  of  albumin  contains  four  times  as  much  pepsin 
as  one  which  digests  only  i  mm.  of  albumin. 

Example. — If  the  microscopic  reading  gives  on  an  average  2.2  mm.  of  albumin 
digested  the  pepsin  value  for  the  diluted  juice  would  be  2.2 2  =  4.84,  and  for  the 
pure  undiluted  juice,  4.84X16  =  77.44. 

Preparation  of  Mett  Tubes  (Christiansen's  Method}.1 — The  liquid  portions  of 
the  whites  of  several  eggs  are  mixed  and  strained  through  cheese  cloth.  The  mix- 
ture should  be  homogeneous  and  free  from  air  bubbles.  It  is  best  to  allow  the 
egg-white  to  stand  for  two  or  three  hours  in  a  vacuum  desiccator  to  more  completely 
remove  air.  A  number  of  thin-walled  glass  tubes  of  1-2  mm.  internal  diameter 
are  thoroughly  cleaned  and  dried  and  cut  into  lengths  of  about  10  inches.  These 
are  sucked  full  of  the  egg-white  and  kept  in  a  horizontal  position.  Into  a  large 
evaporating  dish  or  basin  5-10  liters  of  water  are  introduced  and  heated  to  boiling. 
The  vessel  is  then  removed  from  the  fire  and  stirred  with  a  thermometer  until 
the  temperature  sinks  to  exactly  85°C.  The  tubes  filled  with  egg-white  are  im- 
mediately introduced  and  left  in  the  water  until  it  has  cooled.  The  tubes  thus 
prepared  are  soft  boiled,  more  easily  digested  than  hard  boiled  tubes,  and  free 
from  air  bubbles.  The  ends  are  sealed  by  dipping  in  melted  paraffin  or  sealing 
wax  (preferably  the  latter),  and  the  tubes  can  be  kept  thus  for  a  long  time.  When 
ready  for  use  mark  with  a  file  and  break  into  pieces  about  %  inch  long.  After 
cutting,  the  tubes  should  be  immediately  introduced  into  the  digestion  mixture 
or  may  be  kept  a  short  time  under  water.  Tubes  whose  ends  are  not  squarely 
broken  off  must  be  rejected. 

The  digestibility  of  different  egg-whites  varies  widely.  Hence  in  making  up 
a  new  set  of  tubes  if  we  wish  our  results  to  be  comparable  these  tubes  must  be 
standardized  against  those  first  prepared.  This  may  be  done  by  running  simul- 
taneous tests  with  tubes  from  the  two  series,  using  the  same  gastric  juice  and  com- 
paring the  lengths  of  the  columns  digested  in  each  case.  Christiansen's  method  of 
preparing  tubes  of  the  same  digestibility  is  to  be  preferred.  He  proceeds  as  in 
the  original  preparation  of  the  tubes  except  that  as  the  water  cools  from  Qo0-8o°C. 
a  single  tube  containing  the  new  egg-white  is  dropped  in  at  each  degree  change  of 
temperature,  that  is  at  90°,  89°,  etc.  Pieces  of  each  of  these  tubes  as  well  as  of  the 
original  standard  tubes  are  then  allowed  to  digest  simultaneously  in  portions  of  the 

1  Christiansen:  Biochem.  Zeit.,  46,  257,  1912. 


170  PHYSIOLOGICAL   CHEMISTRY 

same  gastric  juice.  One  of  these  tubes  should  show  a  digestibility  equal  to  that 
of  the  standard  tubes.  For  example  the  tube  coagulated  at  88° C.  may  show  the 
proper  digestibility.  Then  the  new  series  of  tubes  should  be  made  in  the  same  man- 
ner as  this  one,  that  is  introduced  at  88°  C.  The  tubes  thus  prepared  should  be 
again  checked  up  with  the  standard  to  see  that  no  mistake  has  been  made. 

(2)  Rose's  Modification1  of  the  Jacoby-Solms  Method.2 — Dissolve  0.25  gram  of 
the  globulin  of  the  ordinary  garden  pea,3  Pisum  sativum,  in  100  c.c.  of  10  per  cent 
sodium  chloride  solution,  warming  slightly  if  necessary. 4  Filter  and  introduce  i  c.c. 
of  the  clear  nitrate  into  each  of  a  series  of  six6  test-tubes  about  i  cm.  in  diameter. 
Introduce  into  each  tube  i  c.c.  of  0.6  per  cent  hydrochloric  acid  and  permit  a  period 
of  about  five  minutes  to  elapse  for  the  development  of  the  turbidity.  Make  a 
known  volume  of  the  gastric  juice  (5-10  c.c.  is  sufficient)  exactly  neutral  to  litmus 
paper  with  dilute  alkali;  and  record  the  volume  of  the  alkali  so  used.  If  acid 
metaprotein  precipitates,  filter  it  off;  if  there  is  no  precipitate  proceed  without 
filtration.  Dilute  the  clear  neutral  solution  with  a  known  quantity  of  distilled 
water  (usually  5  volumes)  making  proper  allowance  for  the  volume  of  alkali  used  in 
the  neutralization.  Boil  5-10  c.c.  of  the  diluted  juice,  filter  and  add  the  following 
decreasing  volumes  (c.c.)  to  the  series  of  six  tubes:  i.o,  0.9,  0.7,  0.5,  0.2,  o.o.  Make 
the  measurements  by  means  of  a  i  c.c.  pipette  graduated  in  o.oi  c.c.  Now  rapidly 
introduce  the  unboiled,  diluted  juice  in  the  following  increasing  volumes  (c.c.)  in 
order:  o.o,  o.i,  0.3,  0.5,  0.8,  i.o.  Each  tube  now  contains  a  total  volume  of  3  c.c. 
and  a  total  acidity  of  0.2  per  cent  hydrochloric  acid.  Shake  each  tube  thoroughly 
and  place  them  at  5o-52°C.  for  15  minutes  or  at  35-36°C.  for  one  hour.  Examine 
the  series  of  tubes  at  the  end  of  the  digestion  period  and  select  that  tube  which 
contains  the  smallest  quantity  of  gastric  juice  and  which  shows  no  turbidity.  The 
volume  of  the  juice  used  in  this  tube  is  taken  as  the  basis  for  the  calculation  of  the 
peptic  activity. 

Calculation. — The  peptic  activity  is  expressed  in  terms  of  i  c.c.  of  the  undiluted 
juice.  For  example,  if  it  requires  0.5  c.c.  of  the  diluted  juice  (five-fold  dilution)  to 
clear  up  the  turbidity  in  i  c.c.  of  the  globulin  solution  in  the  proper  experimental 
time  interval  (15  minutes  or  one  hour  according  to  temperature)  the  peptic  activity 
would  be  expressed  as  follows: 

(i-5-o.s)X5  =  i°  (peptic  activity). 

1Rose:  Archives  of  Internal  Medicine,  5,  459,  1910. 
2Solms:  Zeitschriftfur  klinische  Medizin,  64,  159,  1907. 

3  The  globulin  may  be  prepared  as  follows:  "The  finely  ground  peas,  freed  as  much  as 
possible  from  the  outer  coating,  are  repeatedly  extracted  with  large  quantities  of  10  per  cent 
sodium  chloride  solution,  the  extracts  combined,  strained  through  fine  bolting-cloth,  and 
allowed  to  stand  over  night  in  large  cylinders  to  deposit  insoluble  matter.    The  supernatant 
fluid  is  siphoned  off  and  saturated  with  ammonium  sulphate.     The  precipitate  of  albumin 
and  globulin  is  filtered  off,  suspended  in  a  little  water,  and  dialyzed  in  running  water  for 
three  days,  until  the  salt  has  been  removed,  and  the  albumins  have  been  dissolved.     The 
globulins  are  filtered  off  and  washed  two  or  three  times  to  remove  the  last  trace  of  albumins. 
To  purify  further,  the  precipitate  is  extracted  with  10  per  cent  sodium  chloride  solution,  and 
filtered  until  perfectly  clear.     The  resulting  solution  is  neutralized  to  litmus  paper  by  the 
cautious  addition  of  dilute  sodium  hydroxide,  and  again  dialyzed  in  running  water  for  three 
days  to  remove  the  salts  completely.    The  precipitated  globulins  are  then  filtered  off  and 
dried  on  a  water-bath  at  4o°C.     During  the  entire  process  of  separation  the  proteins  should 
be  preserved  with  a  mixture  of  alcoholic  thymol  and  toluol."    This  dried  globulin  is  used  in 
the  clinical  procedure. 

4  This  solution  may  be  preserved  at  least  two  months  under  toluene. 

6  A  longer  series  of  tubes  may  be  used  if  desired.  However,  experience  has  shown  that 
a  series  of  six  ordinarily  affords  sufficient  range  for  all  diagnostic  purposes. 


GASTRIC  ANALYSIS  171 

According  to  this  scale  of  pepsin  units  10  may  be  considered  as  "normal"  peptic 
activity.  These  units  are  about  Ko  as  large  as  those  expressed  by  the  Jacoby- 
Solms  scale. 

Inasmuch  as  it  has  been  shown1  that  blood  serum  contains  an  antipepsin  it  is 
said  to  be  advisable  to  test  the  gastric  juice  for  blood  before  determining  its  pro- 
teolytic  power.  However,  Dezani2  claims  that  the  methods  for  demonstrating 
antipepsin  in  the  blood  are  not  adequate. 

(3)  Given's  Modification  of  Rose's  Method.3 — The  gastric  contents  are  strained 
through  cheese  cloth.  Two  c.c.  are  measured  by  means  of  an  Ostwald  pipette 
into  a  25  c.c.  stoppered  volumetric  cylinder,  and  diluted  to  the  mark  with  dis- 
tilled water.  Into  each  of  seven  small  test-tubes  (1X10  cm.)  is  measured,  with 
an  Ostwald  pipette,  i  c.c.  of  a  0.25  per  cent  filtered  pea  globulin  in  10  per  cent 
sodium  chloride  solution.  To  each  tube  is  added  i  c.c.  of  0.6  per  cent  hydro- 
chloric acid,  also  by  means  of  an  Ostwald  pipette.  The  tubes  are  allowed 
to  stand  about  five  minutes,  until  the  maximum  turbidity  develops.  To  the 
first  five,  distilled  water  is  added  as  follows:  To  the  first,  0.9  c.c.;  to  the  second, 
0.8  c.c.;  to  the  third,  0.7  c.c.;  to  the  fourth,  0.6  c.c'.;  and  to  the  fifth,  0.2  c.c.;  to 
the  sixth  and  seventh,  none.  Then  there  are  rapidly  added  to  each  test-tube 
the  following  amounts  of  the  diluted  (1:12.5)  gastric  juice;  to  the  first,  o.i  c.c.;  to 
the  second,  0.2  c.c.;  to  the  third,  0.3  c.c.;  to  the  fourth,  0.5  c.c.;  to  the  fifth,  0.8  c.c.; 
to  the  sixth,  i.o  c.c.;  and  to  the  seventh,  i.o  c.c.  of  the  diluted  juice  boiled.  These 
measurements  can  be  accurately  made  with  a  i  c.c.  pipette  graduated  in  o.oi  c.c. 
All  tubes  are  then  immersed  for  15  minutes  in  a  water-bath  at  50°  to  52°C.  At  the 
end  of  this  time,  the  tube  is  selected  which  is  clear  and  contains  the  least  amount  of 
diluted  gastric  juice.  Upon  this  basis,  the  peptic  activity  is  calculated  as  the  num- 
ber of  cubic  centimeters  of  0.25  per  cent  globulin  digested  by  i  c.c.  of  undiluted 
gastric  juice.  For  example,  if  tube  2  containing  0.3  c.c.  of  a  12.5  times  diluted 
juice  be  clear,  then  the  result  would  be  expressed: 

Peptic  activity  =t(i ^-0.3)  X 12. 5  =  41. 2. 

Ordinarily  this  scheme  of  seven  tubes  is  used,  though  it  is  not  a  rule.  If  the 
free  acidity  be  high,  sometimes  a  dilution  of  ^5  is  made.  The  number  of  tubes 
used  will  depend  upon  the  accuracy  desired. 

(d)  Determination  of  Tryptic  Activity. — Trypsin  is  not  a  gastric 
enzyme  but  occurs  in  the  pancreatic  juice  (see  page  190).  In  case  of 
regurgitation  of  intestinal  contents  through  the  pylorus  trypsin  would 
be  passed  into  the  stomach.  This  regurgitation  is  doubtless  of  frequent 
occurrence  and  may  even  be  a  normal  mechanism  by  which  gastric 
acidity  is  regulated  (see  page  153).  Trypsin  is,  therefore,  generally 
present  in  the  contents  of  the  normal  human  stomach.  Inasmuch, 
however,  as  trypsin  is  destroyed  by  the  pepsin-hydrochloric  acid  of 
the  gastric  juice,  determinations  of  this  enzyme  must  be  carried  out 
immediately  after  aspirations  of  the  gastric  contents,  particularly 
where  the  acidity  of  the  latter  is  high. 

lOgur(K  Biochemische  Zeitschrift,  22,  266,  1909. 

'Dezani:  Arch. farm.  Oper.,  22,  287,  1916. 

'Givens:  Hygienic  Lab.  Bull.  101,  p.  71,  August,  1915. 


172  PHYSIOLOGICAL  CHEMISTRY 

Spencer's  Method.1 — (a)  Prepare  five  reagent  tubes,  Nos.  i,  2,  3,  4,  and  5;  more 
if  desired. 

To  tubes  i  and  2  add  0.5  c.c.  of  gastric  contents  (filter  if  cloudy). 

(b)  To  tubes  2,  3,  4,  and  5  add  0.5  c.c.  of  distilled  water. 

(c)  From  tube  2  remove  0.5  c.c.  of  its  mixed  contents  and  add  to  tube  3.    Mix 
thoroughly  and  add  0.5  c.c.  from  tube  3  to  tube  4.    Repeat  for  tube  5. 

We  now  have  dilutions  of  gastric  contents  of  i,  ^,  ^,  ^,  and  KG- 

(d)  To  each  tube  add  one  drop  of  phenolphthalein  solution  (phenolphthalein 
i  gram;  alcohol  (95  per  cent)  100  c.c.);  then  add  drop  by  drop  a  2  per  cent  sodium 
carbonate  solution  until  a  light  pink  color  is  produced. 

(e)  To  tubes  i,  2,  3,  and  4  add  0.5  c.c.  of  casein  solution.    Tube  5  must  receive 
i  c.c.  of  casein  solution,  since  it  contains  i  c.c.  of  the  diluted  gastric  contents.     For 
the  casein  solution,  dissolve  0.4  gram  of  casein  in  40  c.c.  of  N/io  NaOH.    Add  130 
c.c.  of  distilled  water,  then  30  c.c.  of  N/io  HC1.    This  leaves  the  solution  alkaline 
to  the  extent  of  10  c.c.  of  N/io  NaOH,  minus  about  3  c.c.  neutralized  by  the 
casein. 

(/)  Incubate  for  five  hours  at  40° C. 

(g)  Precipitate  the  undigested  casein  by  dropwise  addition  of  a  solution  of  the 
following  composition:  glacial  acetic  acid  i  c.c.,  alcohol  (95  per  cent)  50  c.c.,  dis- 
tilled water  50  c.c.  The  tubes  in  which  digestion  has  been  complete  remain  clear; 
others  become  turbid. 

(h)  The  tryptic  values  are  expressed  in  terms  of  dilution.  Thus,  complete 
digestion  in  tube  3  (a  dilution  of  y±)  shows  four  times  the  tryptic  power  of  un- 
diluted gastric  juice;  taken  as  a  standard  as  i,  therefore,  its  tryptic  value  is  4. 

(i)  Controls  of  boiled  gastric  contents  plus  casein  solution,  and  of  distilled  water 
plus  casein  solution,  treated  as  above  stated,  must  show  no  digestion,  and  become 
turbid  on  addition  of  the  precipitating  solution. 

(e)  Detection  of  Lactic  Acid. — When  the  acidity  of  the  stomach 
contents  is  reduced  to  a  low  value  there  may  occur  considerable  fermen- 
tation of  carbohydrates  which  have  been  introduced  into  the  stomach 
in  the  ingested  food.  This  fermentation  yields  various  organic  acids 
among  which  lactic  acid  is  particularly  prominent.  It  is  important, 
therefore,  in  case  of  low  gastric  acidity  that  the  stomach  contents  be 
examined  for  lactic  acid. 

Tests,  i.  Ether-Ferric  Chloride  Test  (Strauss). — A  satisfactory 
deduction  regarding  the  presence  of  lactic  acid  can  only  be  made  by 
removing  the  lactic  acid  from  disturbing  factors  (e.g.,  hydrochloric  acid, 
protein  digestion  products,  etc.)  present  in  the  stomach  contents. 
Lactic  acid  may  be  extracted  from  the  stomach  contents  by  ether. 
The  following  technic  not  only  serves  to  detect  lactic  acid  but  also  gives 
an  approximate  idea  as  to  the  amount  of  the  acid  present. 

Procedure. — Introduce  5  c.c.  of  strained  stomach  contents  into  a  small  grad- 
uated separately  funnel,  add  20  c.c.  of  ether  and  shake  the  mixture  thoroughly. 

Elaborated  by  Dr.  W.  H.  Spencer  (Jour.  Biol.  Chem.,  21, -165,  1915)  in  the  author's 
laboratory  for  the  specific  purpose  of  determining  trypsin  in  gastric  juice.  For  other  tryp- 
sin  methods  see  Chapter  X.  .  V 


GASTRIC   ANALYSIS  173 

Permit  the  ether  to  separate,  then  allow  all  the  fluid  to  run  out  of  the  separatory 
funnel  except  the  upper  5  c.c.  of  ether.  To  this  ether  extract  add  20  c.c.  distilled 
water  and  2  drops  of  a  10  per  cent  solution  of  ferric  chloride  and  shake  the  mix- 
ture  gently.  A  slight  green  color  is  obtained  in  the  presence  of  0.05  per  cent  lac- 
tic acid  whereas  o.i  per  cent  lactic  acid  yields  a  very  intense  yellowish-green  color. 

2.  Ferric  Chloride  Test  (Kelling). — Fill  a  test-tube  with  water,  add  1-2 
drops  of  a  10  per  cent  solution  of  ferric  chloride  and  mix  thoroughly  to  form  a 
liquid  which  is  very  faintly  colored.    Divide  the  solution  into  two  parts  and  keep 
one  part  as  a  control.    To  the  other  part  add  a  small  amount  of  the  strained 
gastric  contents  and  to  the  control  tube  add  a  similar  volume  of  water.    Lactic 
acid  is  indicated  by  the  immediate  development  of  a  distinct  yellow  color  in  the 
tube  containing  the  gastric  contents. 

The  color  in  this  test  is  due  to  the  formation  of  ferric  lactate. 

3.  Uffelmann's  Reaction. — To  5  c.c.  of  Uffelmann's  reagent1  in  a  test-tube 
add  an  equal  volume  of  strained  gastric  juice.    A  canary  yellow  or  greenish- 
yellow  color  develops  if  lactic  acid  be  present  to  the  extent  of  o.oi  per  cent  or  over. 

Other  organic  acid  gives  a  similar  reaction.  Mineral  acids  such  as 
hydrochloric  acid  discharge  the  blue  coloration  leaving  a  colorless 
solution.  In  other  words,  the  color  of  the  reagent  is  weakened  in  the 
presence  of  an  acid  reaction. 

4.  Hopkins'  Thiophene  Reaction. — Place  about  5  c.c.  of  concentrated  sulphuric 
acid  in  a  test-tube  and  add  i  drop  of  a  saturated  solution  of  copper  sulphate.3 
Introduce  a  few  drops  of  the  gastric  contents,  shake  the  tube  well,  and  immerse  it 
in  the  boiling  water  of  a  beaker-water-bath  for  one  or  two  minutes.     Now  remove 
the  tube,  cool  it  under  running  water,  add  2-3  drops  of  a  dilute  alcoholic  solution8 
of  thiophene,  C4H4S,  from  a  pipette,  replace  the  tube  in  the  beaker  and  carefully 
observe  any  color  change  which  may  occur.    Lactic  acid  is  indicated  by  the  ap- 
pearance of  a  bright  cherry-red  color  which  forms  rapidly.     This  color  may  be  made 
more  or  less  permanent  by  cooling  the  tube  as  soon  as  the  color  is  produced.     Ex- 
cess of  thiophene  produces  a  deep  yellow  or  brown  color  with  sulphuric  acid.     The 
test  is  not  wholly  specific  though  the  author  claims  it  to  be  more  so  than  Uffelmann's 
reaction. 

(f)  Detection  of  Occult  Blood.4— i.  Ortho-tolidin  Test  (Ruttan  and  Hardisty).5 
— To  i  c.c.  of  a  4  per  cent  glacial  acetic  acid  solution  of  o-tolidin6  in  a  test-tube  add 
i  c.c.  of  the  gastric  juice  under  examination  and  i  c.c.  of  3  per  cent  hydrogen 
peroxide.  In  the  presence  of  blood  a  bluish  color  develops  (sometimes  rather 
slowly)  and  persists  for  some  time  (several  hours  in  some  instances). 

1  Uffelmann's  reagent  is  prepared  by  adding  ferric  chloride  solution  to  a  i  per  cent  solu- 
tion of  carbolic  acid  until  an  amethyst-blue  color  is  obtained,  due  in  part  to  the  formation  of 
a  ferric  salt  of  carbolic  acid  and  in  part  to  the  reduction  of  some  of  the  iron. 

2  This  is  added  to  catalyze  the  oxidation  which  follows. 

3  About  10-20  drops  in  100  c.c.  of  95  per  cent  alcohol. 

4  These  tests  may  be  made  upon  the  strained  stomach  contents  or  upon  the  solid  residue. 
6  Ruttan  and  Hardisty:  Canadian  Medicine  Ass'n  Journal,  Nov.,  1912;  also  Biochem. 

Bull.,  2,  225,  1913. 

°NH2  NH2 


CH  CH, 


174  PHYSIOLOGICAL   CHEMISTRY 

This  test  is  said  to  be  as  sensitive  for  the  detection  of  occult  blood  in 
feces  and  stomach  contents  as  is  the  benzidine  reaction.  It  is  also 
claimed  to  be  more  satisfactory  for  urine  than  any  other  blood  test. 
The  acetic  acid  solution  may  be  kept  for  one  month  with  no  reduction  in 
delicacy. 

2.  Benzidine  Reaction. — This  is  one  of  the  most  delicate  of  the  reactions  for  the 
detection  of  blood.  Different  benzidine  preparations  vary  greatly  in  their  sensi- 
tiveness, however.  Inasmuch  as  benzidine  solutions  change  readily  upon  contact 
with  light  it  is  essential  that  they  be  kept  in  a  dark  place.  The  test  is  per- 
formed as  follows :  To  a  saturated  solution  of  benzidine  in  alcohol  or  glacial  acetic 
acid  add  an  equal  volume  of  3  per  cent  hydrogen  peroxide  and  i  c.c.  of  the  gastric 
contents  under  examination.  If  the  mixture  is  not  already  acid  render  it  so  with 
acetic  acid,  and  note  the  appearance  of  a  blue  color.  A  control  test  should  be 
made  substituting  water  for  the  solution  under  examination. 

The  sensitiveness  of  the  benzidine  reaction  is  greater  when  applied 
to  aqueous  solutions  than  when  applied  to  the  urine.  According  to 
Ascarelli  the  benzidine  reaction  serves  to  detect  blood  when  present  in 
a  dilution  of  i  :  300,000.  (For  further  discussion  of  this  test  see 
chapter  on  Blood.) 

(g)  Detection  of  Bile  in  Stomach  Contents. — If  we  accept  BoldyrefTs 
theory  as  to  the  automatic  regulation  of  gastric  acidity1  under  normal 
conditions  by  the  regurgitation  of  alkaline  material  from  the  intestine, 
then  the  presence  of  bile  in  the  gastric  juice  does  not  possess  the  clinical 
significance  it  has  been  accorded.  However,  if  an  ordinary  Ewald  meal 
be  fed,  and  bile  in  any  considerable  quantity  be  found  throughout  the 
entire  course  of  digestion  it  may  indicate,  pathologically,  a  stenosis 
below  the  level  of  the  common  bile  duct.  Frequently  samples  of 
gastric  contents  are  encountered  which  are  uncolored  and  which  never- 
theless contain  bile.  It  is  also  true  that  bile  may  be  adsorbed  from 
stomach  contents  by  mucus  and  food  rests.  The  regulation  technic  for 
bile  testing  is  often  inadequate  to  demonstrate  the  presence  of  this 
fluid  in  gastric  contents.  The  following  procedure  based  upon  the 
oxidation  of  the  bilirubin  with  nitric  acid  forming  green  biliverdin  is 
delicate  and  easy  of  application. 

Procedure. — Saturate  10  c.c.  of  the  fluid  portion  of  the  stomach  contents  with 
powdered  ammonium  sulphate.  This  may  be  accomplished  by  shaking  for  one 
to  two  minutes.  It  generally  requires  about  i  inch  of  powdered  sulphate  in 
the  bottom  of  an  ordinary  test-tube  to  obtain  full  saturation.  When  the  fluid  is 
saturated  add  1-3  c.c.  of  acetone  and  thoroughly  mix  the  contents  of  the  tube  by 
inverting  the  tube  five  or  six  times.  (It  is  better  not  to  shake.)  Permit 
the  tube  to  stand  and  allow  the  acetone  to  rise  to  the  surface.  This  acetone  con- 
tains the  bile  pigment  if  any  is  present  in  the  stomach  contents.  Allow  a  drop 

^oldyreff:  Quart.  Jour.  Exp.  Med.,  8,  i,  1914. 


GASTRIC  ANALYSIS 


175 


of  yellow  nitric  acid  to  flow  down  the  side  of  the  tube  and  note  the  green  color  in 
the  acetone. 

This  green  color  is  biliverdin  which  has  been  produced  from  the 
bilirubin  by  oxidation  with  nitric  acid.  If  too  much  acid  is  added 
the  green  color  will  be  oxidized  to  a  purple  or  red.  If  the  acetone  does 
not  rise  to  the  surface  promptly  the  liquid  has  not  been  completely 
saturated  with  ammonium  sulphate. 

If  the  stomach  contents  contains  large  amounts  of  bile  as  indicated 
by  a  deep  green  color,  4-5  drops  of  the  fluid  may  be  diluted  with  10  c.c. 
water  and  the  above  test  applied. 


FIG.  55. — MICROSCOPICAL  CONSTITUENTS  OF  THE  GASTRIC  CONTENTS. 
Ay  Starch  cells;  B,  yeast  cells;  C,  Oppler-Boas  bacilli;  D,  staphylococci;  E,  streptococci; 
F,  sarcinae;  G,  muscle  fibre;  H,  mucus;  7,  red  blood  cells;  /,  leucocytes;  K,  snail-like  mucus 
formations;  L,  squamous  epithelial  cell;  M,  cellulose. 

(h)  Microscopy  of  the  Gastric  Contents. — A  microscopical  exami- 
nation of  the  gastric  contents  is  a  routine  clinical  procedure. 

When  an  Ewald  meal  is  given  the  starch  granules  in  various  stages 
of  digestion  are  observed  together  with  epithelia  from  the  pharynx, 
esophagus,  and  occasionally  the  stomach.  Gastric  and  salivary 
mucus  are  seen  and  readily  recognized  by  their  ropy  appearance. 
Pathologically  various  bacteria  are  seen,  sarcinae,  Oppler-Boas  bacilli, 
streptococci,  leptothrix,  etc.  Retained  food  from  previous  meals  is 
readily  recognized  by  its  histological  appearance;  meat  fibers,  vegetable 
cells,  and  cellulose  may  all  occur  in  pathological  retention.  In  certain 


176  PHYSIOLOGICAL   CHEMISTRY 

pathological  processes  such  as  ulcer  and  cancer,  red  blood  cells,  pus, 
and  even  the  cancer  cells  themselves  may  be  found.  For  illustrations 
of  the  microscopical  constituents  of  gastric  contents,  see  Fig.  55, 

Procedure. — Examine  a  drop  of  the  original  (mixed)  stomach  contents  un- 
stained under  the  low  and  high  powers  of  the  microscope.  Compare  your  find- 
ings with  the  microscopical  views  shown  in  Fig.  55. 

Wolff  Technic  for  the  Protein  Concentration  of  the  Gastric  Contents.1 — 
Owing  to  the  diagnostic  importance  of  the  protein  concentration  of  the  gastric 
secretion,  a  short  note  of  this  test  is  given  here.  Under  normal  conditions  the 
protein  concentration  follows  that  of  acidity  rather  closely.  In  certain  cases,  how- 
ever, such  as  carcinoma  (Fig.  53),  there  is  an  actual  increase  in  the  protein  concen- 
tration of  the  gastric  juice  out  of  all  proportion  to  the  acidity.  The  test  may  be 
made  as  follows:  The  regular  Ewald  test  meal  is  fed  and  specimens  of  the  gastric 
contents  are  obtained  at  i5-minute  intervals  by  means  of  the  Rehfuss  tube.  One 
c.c.  of  the  filtered  juice  is  then  diluted  with  9  c.c.  of  water  representing  a  dilution 
of  i  :io;  5  c.c.  of  this  mixture  is  again  added  to  5  c.c.  of  water  and  a  dilution  of  i  :2O 
obtained;  this  is  again  repeated  using  5  c.c.  of  the  mixture  last  obtained  and  5  c.c. 
of  distilled  water  and  the  dilutions  are  kept  up  until  a  series  is  obtained  representing 
1:10,  1:20,  1:40,  1:80,  1:160,  1:320,  and  if  necessary  1:640  or  more.  They  are 
then  stratified  with  approximately  i  c.c.  of  Wolff's  reagent,2  care  being  taken  that 
the  liquids  do  not  mix.  The  tubes  should  be  read  immediately  against  a  dark 
background  and  the  tube  giving  a  protein  ring  at  the  greatest  dilution  of  gastric 
juice  recorded.  A  glance  at  Fig.  53  will  show  a  pronounced  case  of  gastric  carci- 
noma. With  normal  acid  figures  the  protein  concentration  evolves  proportionally 
to  the  acidity.  A  case  of  achylia  is  shown  in  Fig.  54. 

Tb'pfer's  Method  of  Gastric  Analysis 

This  method  is  much  less  elaborate  than  many  others  but  is  sufficiently  ac- 
curate for  ordinary  clinical  purposes.  The  method  embraces  the  volumetric  de- 
termination of  (i)  total  acidity,  (2)  free  acidity  (organic  and  inorganic) ,3  and  (3)  free 
hydrochloric  acid,  and  the  subsequent  calculation  of  (4)  combined  acidity  and  (5) 
acidity  due  to  organic  acids  and  acid  sails,  from  the  data  thus  obtained. 

Procedure. — Feed  the  Ewald  test  meal  as  directed  on  page  165.  At  the  end  of 
one  hour  remove  the  entire  stomach  contents  and  analyze  as  directed  below.  This 
method  of  procedure  is  less  accurate  than  the  Fractional  Method  (see  page  150). 
Measure  the  volume  of  the  gastric  contents,  strain  it  through  cheese  cloth  and  intro- 
duce 10  c.c.  of  the  strained  material  into  each  of  three  small  beakers  or  porcelain 
dishes.4  Label  the  vessels  A,  B,  and  C,  respectively,  and  proceed  with  the  analysis 

1  Wolff:  Magen-  und  Darmkrankh.,  Berlin,  1912,  p.  217;  also  Berl.  klin.  Woch.t  May  29, 
1911,  and  March  18,  1912. 

Rolph:  Med.  Rec.,  1913,  p.  848. 

Clarke  and  Rehfuss:  Jour.  Am.  Med.  Ass'n,  64,  1737,  1915. 

2  Phosphotungstic  acid 0.3  gm. 

Concentrated  hydrochloric  acid i .  o  c.c. 

Alcohol  95  per  cent 20 .  o  c.c. 

Distilled  water  sufficient  to  make 200. o  c.c. 

8  For  a  discussion  of  combined  acid  see  chapter  on  Gastric  Digestion. 
4  If  sufficient  gastric  juice  is  not  available  it  may  be  diluted  with  water  or  a  smaller 
amount,  e.g.,-  5  c.c.,  taken  for  each  determination. 


GASTRIC  ANALYSIS  177 

according  to  the  directions  given  below.  The  volume  of  fluid  present  in  the  stomach 
one  hour  after  an  Ewald  meal  varies  under  normal  conditions  between  50  and  100 
c.c.  In  cases  of  hypersecretion  or  defective  motility  200-300  c.c.  may  be  found. 
Very  excessive  volumes,  e.g.,  500-3000  c.c.,  are  indicative  of  dilatation  of  the 
stomach  and  suggest  pyloric  stenosis,  either  benign  or  malignant. 

i.  Total  Acidity.1 — Add  3  drops  of  a  i  per  cent  alcoholic  solution  of  phenol- 
phthalein2  to  the  contents  of  vessel  A  and  titrate  with  N/io  sodium  hydroxide  solu- 
tion until  Si  faint  pink  color  is  produced  and  persists  for  almost  two  minutes.  Take 
the  burette  reading  and  calculate  the  total  acidity. 

Calculation. — The  total  acidity  may  be  expressed  in  the  following  ways: 

1.  The  number  of  cubic  centimeters  of  N/io  sodium  hydroxide  solution  neces- 
sary to  neutralize  100  c.c.  of  gastric  juice. 

2.  The  weight  (in  grams)  of  sodium  hydroxide  necessary  to  neutralize  100  c.c. 
of  gastric  juice. 

3.  The  weight  (in  grams)  of  hydrochloric  acid  which  the  total  acidity  of  100 
c.c.  of  gastric  juice  represents,  i.e.,  percentage  of  hydrochloric  acid. 

The  forms  of  expression  most  frequently  employer!  are  i  and  3,  preference  being 
given  to  the  former,  particularly  in  clinical  work. 

In  making  the  calculation  note  the  number  of  cubic  centimeters  of  N/io  sodium 
hydroxide  required  to  neutralize  10  c.c.  of  the  gastric  juice  and  multiply  it  by  10  to 
obtain  the  number  of  cubic  centimeters  necessary  to  neutralize  100  c.c.  of  the  fluid. 
If  it  is  desired  to  express  the  acidity  of  100  c.c.  of  gastric  juice  in  terms  of  hydro- 
chloric acid,  by  weight,  multiply  the  value  just  obtained  by  0.00365.* 

2.  Free  Acidity  (Organic  and  Inorganic).— Add  3  drops  of  sodium  alizarin 
sulphonate  solution4  to  the  contents  of  vessel  B  and  tirate  with  N/io  sodium  hy- 
droxide solution  until  a  violet  color  is  produqed.     In  this  titration  the  red  color, 
which  appears  after  the  tinge  of  yellow  due  to  the  addition  of  the  indicator  has 
disappeared,  must  be  entirely  replaced  by  a  distinct  violet  color.    Take  the  burette 
reading  and  calculate  the  free  acidity  due  to  organic  and  inorganic  acids. 

Calculation.— Since  the  indicator  used  reacts  to  both  organic  and  inorganic 
acids,  the  number  of  cubic  centimeters  of  N/io  sodium  hydroxide  used  indicates 
the  free  acidity  of  10  c.c.  of  gastric  juice.  The  data  for  100  c.c.  of  gastric  juice  may 
be  calculated  according  to  the  directions  given  under  Total  Acidity,  page  166. 

3.  Free  Hydrochloric  Acid.5 — Add  4   drops  of  di-methyl-amino-azobenzene 
(Topfer's  reagent)  solution6  to  the  contents  of  the  vessel  C  and  titrate  with  N/io 
sodium  hydroxide  solution  until  the  initial  red  color  is  replaced  by  orange  yellow.1 
Take  the  burette  reading  and  calculate  the  free  acidity. 

Calculation. — The  indicator  used  reacts  only  to  free  hydrochloric  acid,  hence  the 
number  of  cubic  centimeters  of  N/io  sodium  hydroxide  used  indicates  the  volume 
necessary  to  neutralize  the  free  hydrochloric  .acid  of  10  c.c.  of  gastric  juice.  To 
determine  the  data  for  100  c.c.  of  gastric  juice  proceed  according  to  the  directions 
given  under  Total  Acidity,  page  165. 

1  This  includes  free  and  combined  acid  and  acid  salts. 

2  One  gram  of  phenolphthalein  dissolved  in  100  c.c.  of  95  per  cent  alcohol. 

3  One  c.c.  of  N/io  hydrochloric  acid  contains  0.00365  gram  of  hydrochloric  acid. 

4  One  gram  of  sodium  alizarin  sulphonate  dissolved  in  100  c.c.  of  water. 

5  Hydrochloric  acid  not  combined  with  protein  material. 

6  One-half  gram  dissolved  in  100  c.c.  of  95  per  cent  alcohol. 

7  If  the  orange  yellow  color  appears  as  soon  as  the  indicator  is  added  it  denotes  the  ab- 
sence of  free  acid. 


178  PHYSIOLOGICAL   CHEMISTRY 

4.  Combined  Acidity. — This  value  may  be  obtained  by  subtracting  the  number 
of  cubic  centimeters  of  N/io  sodium  hydroxide  used  in  neutralizing  the  contents  of 
vessel  B  from  the  number  of  cubic  centimeters  of  N/io  sodium  hydroxide  used  in 
neutralizing  A.    The  data  for  100  c.c.  of  gastric  juice  may  be  calculated  according 
to  directions  given  under  Total  Acidity,  page  165. 

5.  Acidity  Due  to  Organic  Acids  and  Acid  Salts.— This  value  may  be  conven- 
iently calculated  by  subtracting  the  number  of  cubic  centimeters  of  N/io  sodium 
hydroxide  used  in  neutralizing  the  contents  of  vessel  C  from  the  number  of  cubic 
centimeters  of  N/io  sodium  hydroxide  solution  used  in  neutralizing  the  contents  of 
vessel  B.    The  remainder  indicates  the  number  of  cubic  centimeters  of  N/io 
sodium  hydroxide  solution  necessary  to  neutralize  the  acidity  due  to  organic  acids 
and  acid  salts  present  in  10  c.c.  of  gastric  juice.    The  data  for  100  c.c.  of  gastric 
juice  may  be  calculated  according  to  directions  given  under  Total  Acidity,  page  165. 


CHAPTER  IX 
FATS 

Fats  occur  very  widely  distributed  in  the  plant  and  animal  king- 
doms, and  constitute  the  third  general  class  of  food-stuffs.  In  plant 
organisms  they  are  to  be  found  in  the  seeds,  roots,  and  fruit,  while  each 
individual  tissue  and  organ  of  an  animal  organism  contains  more  or  less 
of  the  substance.  In  the  animal  organism  fats  are  especially  abundant 
in  the  bone  marrow  and  adipose  tissue.  They  contain  the  same  ele- 
ments as  the  carbohydrates,  i.e.,  carbon,  hydrogen,  and  oxygen,  but 
the  oxygen  is  present  in  smaller  percentage  than  in  the  carbohydrates 


FIG.  56.^-BEEF  FAT.    (Long.) 

and  the  hydrogen  and  oxygen  are  not  present  in  the  proportion  to  form 
water. 

Chemically  considered  the  fats  are  esters1  of  the  tri-atomic  alcohol, 
glycerol,  and  the  mono-basic  fatty  acids.  In  the  formation  of  these  fats 
three  molecules  of  water  result.  This  water  arises  by  the  replacement 
of  the  H's  of  the  carboxyl  groups  of  the  three  fatty  acid  molecules  by 
the  glycerol  radical,  thus  yielding  the  following  type  of  formula.  In 
this  case  the  combination  is  with  palmitic  acid 

CH2 


CH— OOCCi6H3i 

I 

CH2— OOCCi5H3i 

1  An  ester  is  an  acid,  one  or  more  of  whose  acid  hydrogens  is  replaced  by  an  organic 
radical. 

179 


l8o  PHYSIOLOGICAL    CHEMISTRY 

The  three  fatty  acid  radicals  entering  into  the  structure  of  a  neutral 
fat  may  be  the  radicals  of  the  same  fatty  acid  or  they  may  consist  of 
the  radicals  of  three  different  fatty  acids. 

By  hydrolysis  of  a  neutral  fat,  i.e.,  by  the  addition  to  the  molecule 
of  those  elements  which  are  eliminated  in  the  formation  of  the  fat  from 
glycerol  and  fatty  acid,  it  may  be  resolved  into  its  component  parts, 
*•«•>  glycerol  and  fatty  acid.  In  the  case  of  palmitin  the  following 
would  be  the  reaction: 


Palmitin.  Glycerol.  Palmitic  acid. 

This  process  is  called  saponification  and  may  be  produced  by  boiling 
with  alkalis;  by  the  action  of  steam  under  pressure;  by  long-continued 
contact  with  air  and  light;  by  the  action  of  certain  bacteria  and  by 
fat-splitting  enzymes  or  lipases,  e.g.,  pancreatic  lipase  (see  page  191). 
The  cells  forming  the  wafts  of  the  intestines  evidently  possess  the  pecu- 
liar property  of  synthesizing  the  glycerol  and  fatty  acid  thus  formed  so 
that  after  absorption  these  bodies  appear  in  the  blood  not  in  their 
individual  form  but  as  neutral  fats. 

The  principal  animal  fats  with  which  we  have  to  deal  are  stearin, 
palmitin,  olein,  and  butyrin.  Such  less  important  forms  as  laurin  and 
myristin  may  occur  abundantly  in  plant  organisms.  The  older  system 
of  nomenclature  for  these  fats  was  to  apply  the  prefix  "tri"  in  each 
case  (e.g.,  ^-palmitin)  since  three  fatty  acid  radicals  are  contained  in 
the  neutral  fat  molecule. 

The  fatty  acids  corresponding  to  the  above-mentioned  animal  fats 
are  stearic,  CH3(CH2)i6COOH;  palmitic,  CH3(CH2)i4COOH;  oleic, 
CH3(CH2)7CH  =  CH(CH2)7COOH;  and  butyric,  CH3(CH2)2COOH. 
Stearic,  palmitic  and  butyric  acids  are  saturated  fatty  acids,  whereas 
oleic  acid  belongs  to  the  class  of  unsaturated  acids.  Linoleic  acid  is 
also  unsaturated.  Upon  the  presence  of  these  unsaturated  fatty  acids 
depends  the  property  which  certain  fats  possess  of  absorbing  or  combin- 
ing with  iodine.  The  determination  of  this  so-called  "iodine  absorption 
number"  is  important  in  the  differentiation  of  fats  and  oils.  Fats 
containing  the  unsaturated  acids  oleic  and  linoleic  may  be  transformed 
by  "hydrogenation"1  into  the  fats  containing  the  corresponding 
saturated  acid  (stearic).  The  oleic  acid  is  changed  thus: 

C17H33COOH+2H-*Ci7H35COOH. 

Oleic  acid.  Stearic  acid. 

Fats  occur  ordinarily  as  mixtures  of  several  individual  fats.     For 
1  Addition  of  hydrogen  to  the  molecule,  producing  a"hydrogenatedfat." 


FATS  l8l 

example,  the  fat  found  in  animal  tissues  is  a  mixture  of  olein,  palmitin 
and  stearin,  the  percentage  of  any  one  of  these  fats  present  depending 
upon  the  particular  species  of  animal  from  whose  tissue  the  fat  was 
derived.  Thus  the  ordinary  mutton  fat  contains  more  stearin  and  less 
olein  than  the  pork  fat.  Human  fat  contains  from  67  per  cent  to  85  per 
cent  of  olein  and,  according  to  Benedict  and  Osterberg,  upon  analysis 
yields  76.08  per  cent  of  carbon  and  11.78  per  cent  of  hydrogen.  Butter 
consists  in  large  part  of  olein  and  palmitin.  Stearin,  butyrin,  caproin 
and  traces  of  other  fats  are  also  present. 

Pure  neutral  fats  are  odorless,  tasteless,  and  generally  colorless. 
They  are  insoluble  in  the  ordinary  protein  solvents  such  as  water,  salt 
solutions,  and  dilute  acids  and  alkalis,  but  are  very  readily  soluble  in 
ether,  benzene,  chloroform,  and  boijing  alcohol.  The  neutral  fats  are 
non-volatile  substances  possessing  a  neutral  -reaction.  If  allowed  to 
remain  in  contact  with  the  air  for  a  sufficient  length  of  time  they  become 
yellow  in  color,  assume  an  acid  reaction  and  are  said  to  be  rancid.  The 
neutral  fats  may  be  crystallized,  some  of  them  with  great  facility.  The 
crystalline  forms  of  some  of  the  more  common  fats  are  reproduced  in 
Figs.  56,  57  and  58  on  pages  179,  182  and  184.  Each  individual  fat 
possesses  a  specific  melting-point,  and  this  property  of  melting 
at  a  definite  temperature  may  be  used  as  a  means  of  differentia- 
tion in  the  same  way  as  the  coagulation?  temperature  (see  page  104)  is 
used  for  the  differentiation  for  coagulable  proteins.  When  shaken  with 
'  water,  or  a  solution  of  albumin,  soap,  or  acacia,  the  liquid  fats  are  finely 
divided  and  assume  a  condition  known  as  an  emulsion.  The  emulsion 
with  water  is  transitory,  while  the  emulsions  with  soap,  acacia,  or 
albumin  are  permanent. 

A  mtamine  or  accessory  food  substance  known  as  "  Fat-soluble  A " 
is  present  in  certain  foods,  e.g.  milk,  butter  and  egg  yolk.  It  is  believed 
to  be  absent  from  lard,  olive  oil  and  certain  other  vegetable  oils  (see 
p.  581). 

The  fat  ingested  continues  essentially  unaltered  until  it  reaches  the 
intestine  where  it  is  acted  upon  by  pancreatic  lipase  (steapsin) ,  the  fat- 
splitting  enzyme  of  the  pancreatic  juice  (see  page  191),  and  glycerol 
and  fatty  acid  are  formed.  The  glycerol  is  absorbed  directly.  The 
fatty  acid  thus  formed  unites  with  the  alkalis  of  the  pancreatic  juice 
and  forms  soluble  soaps.  These  soaps  are  readily  absorbed.  That 
bile  is  of  assistance  in  the  absorption  of  fat  is  indicated  by  the 
increase  of  fat  in  the  feces  when  for  any  reason  bile  does  not  pass 
into  the  intestine.  Bloor1  claims  that  neither  petroleum  hydro- 
carbons nor  nonsaponifiable  esters,  e.g.,  wool  fat  (lanolin),  are 

1  Bloor:  Jour.  Biol.  Chem.,  15,  105,  1913. 


1 82  PHYSIOLOGICAL   CHEMISTRY 

absorbed.  He  believes  that  saponification  is  a  necessary  preliminary 
to  absorption. 

It  has  been  shown1  that  the  common  food  fats  are  from  93  to  98 
per  cent  utilized  by  the  normal  human  body. 

The  fat  distributed  throughout  the  animal  body  is  formed  partly 
from  the  ingested  fat  and  partly  from  carbohydrates  and  the  "carbon 
moiety"  of  protein  material.  The  formation  of  adipocere2  and  the 
occurrence  of  fatty  degeneration  are  sometimes  given  as  proofs  of  the 
formation  of  fat  from  protein.  This  is  questioned  by  many  investiga- 
tors. Rather  more  satisfactory  and  direct  proof  of  the  formation  of  fat 
from  protein  material  has  been  obtained  by  Hofmann  in  experimentation 
with  fly-maggots.  The  normal  content  of  fat  in  a  number  of  maggots 
was  determined  and  later  the  fat  content  of  others  which  had  developed 
in  blood  (84  per  cent  of  the  solid  matter  of  blood  plasma  is  protein 
material)  was  determined.  The  fat  content  was  found  to  have  in- 
creased 700  to  1 100  per  cent  as  a  result  of  the  diet  of  blood  proteins. 


FIG.  57. — MUTTON  FAT,    (Long.} 

The  celebrated  experiments  of  Pettenkofer  and  Voit,  however,  have 
furnished  what  is,  perhaps,  the  most  substantial  positive  evidence  of 
the  formation  of  fat  from  protein.  These  investigators  fed  dogs  large 
amounts  of  lean  meat,  daily,  and  through  examination  of  urine,  feces  and 
expired  air  were  enabled  to  account  for  only  part  of  the  ingested  carbon, 
although  obtaining  a  satisfactory  nitrogen  balance.  The  discrepancy 
in  the  carbon  balance  was  explained  upon  the  theory  that  the  protein  of 
the  ingested  meat  had  been  split  into  a  nitrogenous  and  a  non-nitroge- 
nous portion  in  the  organism,  and  that  the  non-nitrogenous  portion,  the 
so-called  "carbon  moiety"  of  the  protein,  had  been  subsequently  trans- 
formed into  fat  and  deposited  as  such  in  the  tissues  of  the  organism. 

1  Holmes  and  Deuel:  Jour.  Biol.  Chem.,  41,  227,  1920. 

2  A  very  complete  analysis  of  adipocere  was  reported  by  Ruttan  and  Marshall  before 
the  Society  of  Biological  Chemists,  Boston,  Dec.  27,  1915.  V 


FATS  183 

Later  evidence  in  favor  of  the  formation  of  fat  from  protein  has 
been  furnished  by  the  experiments  of  Weinland.  This  investigator 
worked  with  the  larvae  of  Calliphora,1  these  larvae  being  rubbed  up 
in  a  mortar2  with  Witte's  peptone  and  water  to  form  a  homogeneous 
mixture.  After  placing  these  mixtures  at  38°C.  for  24  hours  the  fat 
content  was  found  to  have  increased,  as  much  as  140  per  cent  in  some 
instances.  The  active  agency  in  this  transformation  of  fat  is  the  larval 
tissue,  since  the  tissues  of  both  the  dead  and  living  larvae  possess  the 
property.  Data  are  given  from  control  tests  which  show  that  the  action 
of  bacteria  in  this  transformation  of  protein  was  excluded.  Lusk3 
as  the  result  of  experiments  on  dogs  claims  to  have  definitely  demon- 
strated that  fat  may  be  formed  from  protein. 

EXPERIMENTS  ON  FATS 

1.  Solubility. — Test  the  solubility  of  olive  oil  ifl  water,  dilute  acid  and  alkali 
and  in  cold  alcohol,  hot  alcohol,  chloroform,  ether,  and  carbon  tetrachloride. 

2.  Formation  of  a  Transparent  Spot  on  Paper. — Place  a  drop  of  olive  oil 
upon  a  piece  of  ordinary  writing  paper.    Note  the  transparent  appearance  of  the 
paper  at  the  point  of  contact  with  the  fat. 

3.  Reaction. — Try  the  reaction  of  fresh  olive  oil  to  litmus,  Congo  red  and  phe- 
nolphthalein.    Repeat  the  test  with  rancid  olive  oil.4    What  is  the  reaction  of  a 
fresh  fat  and  how  does  this  reaction  change  upon  allowing  the  fat  to  stand  for  some 
time? 

4.  Formation  of  Acrolein. — To  a  little  olive  oil  in  a  mortar  add  some  dry  potas- 
sium bisulphate,  KHSO4,  and  rub  up  thoroughly.    Transfer  to  a  dry  test-tube 
and  cautiously  heat.    Note  the  irritating  odor  of  acrolein.    The  glycerol  of  the 
fat  has  been  dehydrated  and  acrylic  aldehyde  or  acrolein  has  been  produced. 
This  is  the  reaction  which  takes  place : 

CH2OH         CHO 

OH    ->  CH+2H20. 

II 
;H2-OH        CH2 

Glycerol.  Acrolein. 

5.  Emulsification. — (a)  Shake  up  a  drop  of  neutral8  olive  oil  with  a  little  water 
in  a  test-tube.    The  fat  becomes  finely  divided,  forming  an  emulsion.    This 
is  not  a  permanent  emulsion  since  the  fat  separates  and  rises  to  the  top  upon 
standing. 

(b)  To  5  c.c.  of  water  in  a  test-tube  add  2  or  3  drops  of  0.5  per  cent  Na2CO3. 
Introduce  into  this  faintly  alkaline  solution  a  drop  of  neutral  olive  oil  and  shake. 
The  emulsion  while  not  permanent  is  not  so  transitory  as  in  the  cases  of  water  free 
from  sodium  carbonate. 

lThe  ordinary  "blow-fly." 

2  Intact  larvae  were  used  in  some  experiments. 

'Atkinson  and  Lusk:  Proc.  Nat.  Acad.  Sci.,  5,  246,  1919;  Lusk:  Proc.  Soc.  Expt. 
Biol.  and  Med.,  17,  171,  1920. 

4To  prepare  rancid  olive  oil  add  5  drops  of  oleic  acid  to  10  c.c.  of  olive  oil. 

5  Neutral  olive  oil  may  be  prepared  by  shaking  ordinary  olive  oil  with  a  10  per  cent 
solution  of  sodium  carbonate.  This  mixture  should  then  be  extracted  with  ether  and  the 
ether  removed  by  evaporation.  The  residue  is  neutral  olive  oil. 


1 84 


PHYSIOLOGICAL   CHEMISTRY 


(c)  Repeat  (b)  using  rancid  olive  oil.    What  sort  of  an  emulsion  do  you  get 
and  why?    It  is  impossible  to  emulsify  a  highly  rancid  fat  due  to  the  excessive 
formation  of  rather  insoluble  soaps  about  the  oil  drops. 

(d)  Shake  a  drop  of  neutral  olive  oil  with  dilute  albumin  solution.    What  is 
the  nature  of  this  emulsion?    Examine  it  under  the  microscope. 

6.  Fat  Crystals. — Dissolve  a  small  piece  of  lard  in  ether  in  a  test-tube,  add 
an  equal  volume  of  alcohol  and  allow  the  alcohol-ether  mixture  to  evaporate 
spontaneously.    Examine  the  crystals  under  the  microscope  and  compare  them 
with  those  reproduced  in  Figs.  56,  57,  and  58,  on  pages  179,  182  and  184. 

7.  Saponification  of  Bayberry  Tallow.1 — Fill  a  large  casserole  two-thirds 
full  of  water  rendered  strongly  alkaline  with  solid  potassium  hydroxide  (a  stick 
one  inch  in  length).    Add  about  10  grams  of  bayberry  tallow  and  boil,  keeping 
the  volume  constant  by  adding  water  as  needed.    When  saponification  is  com- 


FIG.  58. — PORK  FAT. 

plete2  remove  25  c.c.  of  the  soap  solution  for  use  in  Experiment  8  and  add  concen- 
trated hydrochloric  acid  slowly  to  the  remainder  until  no  further  precipitate  is 
produced.3  Cool  the  solution  and  the  precipitate  of  free  fatty  acid  will  rise  to  the 
surface  and  form  a  cake.  In  this  instance  the  fatty  acid  is  principally  palmitic 
acid.  Remove  the  cake,  break  it  into  small  pieces,  wash  it  with  water  by  decan- 
tation  and  transfer  to  a  small  beaker  by  means  of  95  per  cent  alcohol.  Heat  on  a 
water-bath  until  the  palmitic  acid  is  dissolved,  then  filter  through  a  dry  filter 
paper  and  allow  the  filtrate  to  cool  slowly  in  order  to  obtain  satisfactory  crystals. 
Write  the  reactions  which  have  taken  place  hi  this  experiment. 

When  the  palmitic  acid  has  completely  crystallized  filter  off  the  alcohol,  dry 
the  crystals  between  filter  papers  and  try  the  tests  given  hi  Experiment  10,  p.  185. 

8.  Salting-out  Experiments. — To  25  c.c.  of  soap  solution,  prepared  as  de- 
scribed above,  add  solid  sodium  chloride  to  the  point  of  saturation,  with  continual 
stirring.  A  menstruum  is  thus  formed  in  which  the  soap  is  insoluble.  This 

1  Bayberry  tallow  is  derived  from  the  fatty  covering  of  the  berries  of  the  wax  myrtle.    It 
is  therefore  frequently  called  "myrtle  wax"  or  "bayberry  wax." 

2  Place  2  or  3  drops  in  a  test-tube  full  of  water.    If  saponification  is  complete  the  prod- 
ucts will  remain  in  solution  and  no  oil  will  separate. 

a  Under  some  conditions  a  purer  product  is  obtained  if  the  soap  solution  is  cooled  before 
precipitating  the  fatty  acid. 


FATS 


salting-out  process  is  entirely  analogous  to  the  salting-out  of  proteins  (see  page 
104). 

9.  Formation  of  Insoluble  Soaps. — Introduce  5  c.c.  of  soap  solution  into  each 
of  two  test-tubes.    To  the  contents  of  one  tube  add  a  small  amount  of  a  solution 
of  calcium  chloride  and  to  the  contents  of  the  other  tube  add  a  small  amount 
of  a  solution  of  magnesium  sulphate.    Note  the  formation  of  insoluble  soaps  of 
calcium  and  magnesium. 

10.  Palmitic  Acid. — (a)  Examine  the  crystals  under  the  microscope  and  com- 
pare them  with  those  shown  in  Fig.  59,  below. 

(b)  Solubility. — Try  the  solubility  of  palmitic  acid  in  the  same  solvents  as  used 
on  fats  (see  page  183). 

(c)  Melting-point. — Determine  the  melting-point  of  palmitic  acid  by  one  of 
the  methods  given  on  page  186. 


FIG.  SQ.  —  PALMITIC  ACID. 


(d)  Formation  of  Translucent  Spot  on  Paper.—  Melt  a  little  of  the  fatty  acid 
and  allow  a  drop  to  fall  upon  a  piece  of  ordinary  writing  paper.    How  does  this 
compare  with  the  action  of  a  fat  under  similar  circumstances? 

(e)  Acrolein  Test.—  Apply  the  test  as  given  under  4,  page  183.    Explain  the 
result. 

(f)  Iodine  Absorption  Test.  —  For  directions  see  Experiment  13. 

11.  Saponification  of  Lard.  —  To  25  grams  of  lard  in  a  flask  add  75  c.c.  of 
alcoholic-potash  solution  and  warm  upon  a  water-bath  until  saponification  is 
complete.     (This  point  is  indicated  by  the  complete  solubility  of  a  drop  of  the 
solution  when  allowed  to  fall  into  a  little  water.)    Now  transfer  the  solution  from 
the  flask  to  an  evaporating  dish  containing  about  100  c.c.  of  water  and  heat  on  a 
water-bath  until  all  the  alcohol  has  been  driven  off.    Precipitate  the  fatty  acid 
with  hydrochloric  acid  and  cool  the  solution.    Remove  the  fatty  acid  which  rises 
to  the  surface,1  neutralize  the  solution  with  sodium  carbonate  and  evaporate  to 
dryness.    Extract  the  residue  with  alcohol,  remove  the  alcohol  by  evaporation 
upon  a  water-bath  and  on  the  residue  of  glycerol  thus  obtained  make  the  tests 
as  given  below. 

12.  Glycerol.     (a)  Taste.—  What  is  the  taste  of  glycerol? 

1  After  drying  the  acid  make  an  iodine  absorption  test  as  described  in  Experiment*  13. 


i86 


PHYSIOLOGICAL   CHEMISTRY 


(b)  Solubility. — Try  the  solubility  of  glycerol  in  water,  alcohol  and  ether. 

(c)  Hypochlorite-Orcinol  Reaction.1 — This  is  based  on  the  oxida- 
tion of  glycerol  to  the  corresponding  aldose  sugar  glycerose  and  the 
detection  of  the  latter  by  means  of  orcinol.     Homologues  of  glycerol 
as  well  as  the  corresponding  acids  and  certain  sugars  as  glucose  and 
mannose  give  the  reaction.     The  first  named  occur  seldom  while  the 
latter  may  be  removed  with  baryta. 

Two  to  3  c.c.  of  a  i  per  cent  or  o.i  per  cent  solution  of  glycerol  in  water  is 
treated  with  exactly  3  drops  ( =  0.12  c.c.)  normal  NaOCl2  and  boiled  for  a  minute. 
To  the  liquid  while  still  hot  add  3  drops  of  hydrochloric  acid  (sp.  gr.  1.124)  and 

boil  30-60  seconds  to  drive  off  chlorine,  a 
colorless  solution  being  obtained.  Then  add 
an  equal  volume  of  fuming  hydrochloric  acid  and 
a  small  knife-point  of  orcinol.  On  boiling  the 
mixture  becomes  a  beautiful  violet  or  green  blue. 
The  precipitate  formed  is  soluble  in  amyl  alcohol 
and  may  be  examined  spectroscopically. 

(d)  Acrolein  Test. — Repeat  the  test  as  given 
under  4,  page  183. 

(e)  Borax    Fusion    Test.— Fuse    a    little 
glycerol  on  a  platinum  wire  with  some  powdered 
borax  and  note  the  characteristic  green  flame. 
This  color  is  due  to  the  glycerol  ester  of  boric 
acid. 

(f)  Fehling's  Test— How  does  this  result 
compare  with  the  results  on  the  sugars? 

(g)  Solution   of   Cu(OH)2.    Form   a   little 
cupric  hydroxide   by  mixing  copper  sulphate 
and  potassium  hydroxide.    Add  a  little  glycerol 
to  this  suspended  precipitate  and  note  what 
occurs. 

13.  Iodine    Absorption    Test.— Dissolve   a 
small  amount  of  an  unsaturated  organic  acid, 
e.g.,  oleic  acid,  in  chloroform.    Add  2-3  drops 
of  HiibPs  iodine  solution3  and  shake.    The  solu- 
tion will  be  decolorized  if  unsaturated  acids  .are 
present.    This  is  due  to  the  absorption  of  the 
iodine.    The  test  should  be  controlled  by  shak- 
ing chloroform  and  iodine  solution  to  which  no 
acid  has  been  added. 

14.  Melting-point  of  Fat.— First  Method.— 

Insert  one  of  the  melting-point  tubes,  furnished  by  the  instructor,  into  the 
liquid  fat  and  draw  up  the  fat  until  the  bulb  of  the  tube  is  about  one-half  full 
of  the  material.    Then  fuse  one  end  of  the  tube  in  the  flame  of  a  Bunsen  burner 

lMandel  and  Neuberg:  Bioch.  Zeit.,  71,  214,  1915. 
2 Made  according  to  Raschig:  Ber.,  40,  4586;  1907. 

1  Prepared  by  dissolving  26  grams  of  iodine  and  30  grams  of  mercuric  chloride  in  one 
litre  of  95  per  cent  alcohol. 


FIG.  60. — MELTING-POINT 
APPARATUS. 


FATS  187 

and  fasten  the  tube  to  a  thermometer  by  means  of  a  rubber  band  in  such  a  manner 
that  the  bottom  of  the  fat  column  is  on  a  level  with  the  bulb  of  the  thermometer 
(Pig.  60,  p.  1 86).  Fill  a  beaker  of  medium  size  about  two-thirds  full  of  water  and 
place  it  within  a  second  larger  beaker  which  also  contains  water,  the  two  vessels 
being  separated  by  pieces  of  cork.  Immerse  the  bulb  of  the  thermometer  and 
the  attached  tube  in  such  a  way  that  the  bulb  is  about  midway  between  the 
upper  and  the  lower  surfaces  of  the  water  of  the  inner  beaker.  The  upper 
end  of  the  tube  being  open  it  must  extend  above  the  surface  of  the  surround- 
ing water.  Apply  gentle  heat,  stir  the  water,  and  note  the  temperature  at 
which  the  fat  first  begins  to  melt.  This  point  is  indicated  by  the  initial  trans- 
parency. For  ordinary  fats,  raise  the  temperature  very  cautiously  from  3O°C. 
To  determine  the  congealing-point  remove  the  flame  and  note  the  temperature 
at  which  the  fat  begins  to  solidify.  Record  the  melting-  and  congealing-points 
of  the  various  fats  submitted  by  the  instructor. 

Second  Method. — Fill  a  small  evaporating  dish  about  one-half  full  of  mercury 
and  place  it  on  a  water-bath.  Put  a  small  drop  of  the  fat  under  examination  on  an 
ordinary  cover-glass  and  place  this  upon  the  surface  of  the  mercury.  Raise  the 
temperature  of  the  water-bath  slowly  and  by  means  of  a  thermometer  whose  bulb 
is  immersed  in  the  mercury,  note  the  melting-point  of  the  fat.  Determine  the  con- 
gealing-point by  removing  the  flame  and  leaving  the  fat  drop  and  cover-glass  in 
position  upon  the  mercury.  How  do  the  melting-points  as  determined  by  this 
method  compare  with  those  as  determined  by  the  first  method?  Which  method 
is  the  more  accurate,  and  why? 


CHAPTER  X 
PANCREATIC  DIGESTION1 

As  soon  as  the  food  mixture  leaves  the  stomach  it  comes  into  inti- 
mate contact  with  the  bile  and  the  pancreatic  juice.  Since  these  fluids 
are  alkaline  in  reaction  (see  -Bile,  page  205)  there  can  obviously  be  no 
further  peptic  activity  after  they  have  become  intimately  mixed  with 
the  chyme  and  have  neutralized  the  acidity  previously  imparted  to  it 
by  the  hydrochloric  acid  of  the  gastric  juice.  The  pancreatic  juice 
reaches  the  intestine  through  the  duct  of  Wirsung  which  opens  into  the 
intestine  near  the  pylorus. 

Normally  the  secretion  of  pancreatic  juice  is  brought  about  by  the 
stimulation  produced  by  the  acid  chyme  as  it  enters  the  duodenum. 
Therefore,  any  factor  which  produces  an  increased  flow  of  gastric  juice 
such,  for  example,  as  water2  will  cause  a  stimulation  of  the  pancreatic 
secretion.  The  secretion  of  pancreatic  juice  is  probably  not  due  to  a 
nervous  reflex  as  was  believed  by  Pawlow  but  rather,  as  Bayliss  and 
Starling  have  shown,  is  dependent  upon  the  presence,  in  the  epithelial 
cells  of  the  duodenum  and  jejunum  of  a  body  known  as  prosecretin. 
This  body  is  changed  into  secretin  through  the  hydrolytic  action  of  the 
acid  present  in  the  chyme.  The  secretin  is  then  absorbed  by  the  blood, 
passes  to  the  pancreas  and  stimulates  the  pancreatic  cells,  causing  a 
flow  of  pancreatic  juice.  The  quantity  of  juice  secreted  under  these 
conditions  is  proportional  to  the  amount  of  secretin  present.  The 
activity  of  secretin  solutions  is  not  diminished  by  boiling,  hence  the 
body  does  not  react  like  an  enzyme.  Further  study  of  the  body  may 
show  it  to  be  a  definite  chemical  individual  of  relatively  low  molecular 
weight.  It  has  not  been  possible  thus  far  to  obtain  secretin  from  any 
tissues  except  the  mucous  membrane  of  the  duodenum  and  jejunum. 

This  secretin  mentioned  above  belongs  to  the  class  of  substances 
called  hormones  or  chemical  messengers.  These  hormones  play  a  very 
important  part  in  the  coordination  of  the  activities  of  certain  functions 
and  glands.  Other  important  hormones  are  those  elaborated  by  the 
thyroids,  the  adrenals,  the  pituitary  body  (hypophysis) ,  the  embryo  and 

1  Under  this  head  we  will  consider  only  such  digestive  processes  as  are  brought  about 
by  enzymes  originating  in  the  pancreas.    In  the  following  chapter  on  IntestinaJ  Digestion 
will  be  found  a  consideration  of  such  enzymes  as  have  a  true  intestinal  origin. 

2  See  chapter  on  Gastric  Digestion. 

1 88 


PANCREATIC   DIGESTION  1 89 

the  reproductive  glands.  It  is  claimed  by  some  that  all  active  organs 
of  the  body  produce  hormones. 

The  juice  as  obtained  from  a  permanent  fistula  differs  greatly  in 
its  properties  from  the  juice  as  obtained  from  temporary  fistula,  and 
neither  form  of  fluid  possesses  the  properties  of  the  normal  fluid.  Pan- 
creatic juice  collected  by  Glaessner  from  a  natural  fistula  has  been 
found  to  be  a  colorless,  clear,  strongly  alkaline  fluid  which  foams  readily. 
It  is  further  characterized  by  containing  albumin,  globulin,  proteose, 
and  peptone;  nucleoprotein  is  also  present  in  traces.1  The  average 
daily  secretion  of  pancreatic  juice  is  650  c.c.  and  its  specific  gravity  is 
1.008.  The  fluid  contains  1.3  per  cent  of  solid  matter  and  the  freezing- 
point  is  —  o.47°C.  The  normal  pancreatic  secretion  contains  at  least 
four  distinct  enzymes.  They  are  trypsin,  a  proteolytic  enzyme;  pan- 
creatic amylase  (amylopsin),  an  amylolytic  'enzyme;  pancreatic  lipase 
(steapsin),  a  fat-splitting  enzyme;  and  pancreatic  rennin,  a  milk-coagu- 
lating enzyme. 

The  most  important  of  the  four  enzymes  of  the  pancreatic  juice  is 
the  proteolytic  enzyme  trypsin.  This  enzyme  resembles  pepsin  in  so 
far  as  each  has  the  power  of  breaking  down  protein  material,  but  the 
trypsin  has  much  greater  digestive  power  and  is  able  to  cause  a  more 
complete  decomposition  of  the  complex  protein  molecule.  In  the 
process  of  normal  digestion  the  protein  constituents  of  the  diet  are  for 
the  most  part  transformed  into  proteoses  (albumoses)  and  peptones 
before  coming  in  contact  with  the  enzyme  trypsin.  This  is  not  abso- 
lutely essential,  however,  since  trypsin  possesses  digestive  activity  suffi- 
cient to  transform  unaltered  native  proteins  and  to  produce  from  their 
complex  molecules  comparatively  simple  fragments.  Among  the  prod- 
ucts of  tryptic  digestion  are  proteoses,  peptones,  peptides,  leucine,  tyrosine, 
aspartic  acid,  glutamic  acid,  alanine,  phenylalanine,  glycocoll,  cystine, 
serine,  valine,  proline,  oxyproline,  isoleucine,  arginine,  lysine,  histidine, 
and  tryptophane.  (The  crystalline  forms  of  many  of  these  products  are 
reproduced  in  Chapter  IV.)  Trypsin  does  not  occur  preformed  in  the 
gland,  but  exists  there  as  a  zymogen  called  trypsinogen  which  bears  the 
same  relation  to  trypsin  that  pepsinogen  does  to  pepsin.  Trypsin  has 
never  been  obtained  in  a  pure  form  and  therefore  very  little  can  be 
stated  definitely  as  to  its  nature,  The  enzyme  is  the  most  active  in 
alkaline  solution  but  is  also  active  in  neutral  or  slightly  acid  solutions. 
Trypsin  is  destroyed  by  mineral  acids  and  may  also  be  destroyed  by 
comparatively  weak  alkali  (2  per  cent  sodium  carbonate)  if  left  in  con- 
tact for  a  sufficiently  long  time.  Trypsinogen,  on  the  other  hand,  is 
more  resistant  to  the  actions  of  alkalis.  In  pancreatic  digestion  the  pro- 

1  Glaessner:  Zeilschrift  fur  physiologische  Chemie,  40,  476,  1904. 


I QO  PHYSIOLOGICAL  CHEMISTRY 

tein  does  not  swell  as  is  the  case  in  gastric  digestion,  but  becomes  more 
or  less  "honey-combed' '  and  finally  disintegrates. 

The  presence  of  active  pepsin  in  the  contents  of  the  intestine  has 
been  demonstrated  by  Abderhalden  and  Meyer.1  It  may  possibly  be 
that  pepsin  may  play  a  part  in  the  profound  intestinal  proteolysis  which 
has  up  to  this  time  been  assigned  to  trypsin  and  erepsin  (see  chapter  on 
Gastric  Digestion). 

The  pancreatic  juice  which  is  collected  by  means  of  a  fistula  pos- 
sesses practically  no  power  to  digest  protein  matter.  A  body  called 
enterokinase  occurs  in  the  intestinal  juice  and  has  the  power  of  converting 
trypsinogen  into  trypsin.  This  process  is  known  as  the  "activation"  of 
trypsinogen  and  through  it  a  juice  which  is  incapable  of  digesting  pro- 
tein may  be  made  active.  (For  further  discussion  of  enterokinase 
see  chapter  on  Intestinal  Digestion.)  Mendel  and  Rettger2  and  others 
have  demonstrated  that  activation  of  trypsinogen  into  trypsin  may  be 
brought  about  in  the  gland  as  well  as  in  the  intestine  of  the  living 
organism.  The  manner  of  the  activation  in  the  gland  and  the  nature 
of  the  body  causing  it  are  unknown  at  present.  Prym3  denies  that 
such  an  activation  occurs.  After  the  death  of  the  animal  at  least 
part  of  the  trypsinogen  in  the  pancreas  is  changed  to  trypsin  as  shown 
by  the  fact  that  the  extract  of  the  gland  is  active. 

Delezenne  claims  that  trypsinogen  may  be  activated  by  soluble 
calcium  salts.  He  reports  experiments  which  indicate  that  proteolytic- 
ally  inactive  pancreatic  juice,  obtained  directly  from  the  duct,  when 
treated  with  salts  of  this  character,  assumes  the  property  of  digesting 
protein  material.  This  process  by  which  the  trypsinogen  is  activated 
through  the  instrumentality  of  calcium  salts  is  very  rapid  and  is  desig- 
nated by  Delezenne  as  an  "explosion."  The  suggestion  of  Mays  that 
there  may  possibly  be  several  precursors  of  trypsin  one  of  which  is 
activated  by  enterokinase  and  the  others  by  other  agents,  is  of  interest 
in  this  connection. 

Boldyreff4  has  demonstrated  the  presence  of  trypsin  in  the  stomach 
due  to  the  regurgitation  of  duodenal  contents  through  the  pylorus 
(see  Chapters  VII  and  VIII).  Others5  have  confirmed  this  finding  (see 
chapter  on  Gastric  Analysis). 

Pancreatic  amylase  (amylopsin),  the  second  of  the  pancreatic  en- 
zymes, is  an  amylolytic  enzyme  which  possesses  somewhat  greater  diges- 
tive power  than  the  salivary  amylase  (ptyalin)  of  the  saliva.  As  its 

Abderhalden  and  Meyer:  Zeit.  physiol.  Chem.,  74,  67,  1911. 
2  Mendel  and  Rettger:  American  Journal  of  Physiology,  7. 
3 Prym:  Pfliiger's  Archiv,  104  and  107. 

4Boldyreff:  Transactions  of  the  nth  Pirogoffs  Congress  of  Physicians,  St.  Petersburg, 
1910. 

6 Spencer,  Meyer,  Rehfuss  and  Hawk:  American  Jour.  Physiol.,  39,  459,  1916. 


PANCREATIC  DIGESTION  IQI 

name  implies,  its  activity  is  confined  to  the  starches,  and  the  products 
of  its  amylolytic  action  are  dextrins  and  sugar.  The  sugar  is  principally 
maltose  and  this,  by  the  further  action  of  an  inverting  enzyme  (maltase)  , 
is  transformed  into  glucose. 

It  is  possible  that  the  saliva  as  a  digestive  fluid  is  not  absolutely 
essential.  The  salivary  amylase  (ptyalin)  is  destroyed  by  the  hydro- 
chloric acid  of  the  gastric  juice  and  is  therefore  inactive  when  the  chyme 
reaches  the  intestine.  Should  undigested  starch  be  present  at  this 
point,  however,  it  would  be  quickly  transformed  by  the  active  pancreatic 
amylase.  This  enzyme  is  not  present  in  the  pancreatic  juice  of  infants 
during  the  first  few  weeks  of  life,  thus  showing  very  clearly  that  a  starchy  • 
diet  is  not  normal  for  this  period. 

The  pronounced  influence  of  electrolytes  upon  the  action  of  pancrea- 
tic amylase  and  other  amylases  has  been  demonstrated  many  times.1 
In  fact  the  removal  of  electrolytes  from  pancreatic  juice  by  dialysis 
yields  a  juice  which  possesses  no  power  to  split  starch.  It  also  appears 
that  the  Cl,  Br  and  NOs  ions  have  an  important  stimulating  action*/ 
upon  the  amylases.2 

It  has  been  shown  that  pancreatic  amylase  will  digest  raw  starch. 
The  raw  starch  of  corn  and  wheat  may  be  completely  digested  and 
absorbed  by  normal  adults  whereas  the  raw  potato  starch  is  about 
80  per  cent  available.3 

The  extent  to  which  amylase  is  present  in  the  feces  has  been  taken  as 
the  index  of  pancreatic  activity. 

The  third  enzyme  of  the  pancreatic  juice  is  called  pancreatic  lipase 
(steapsin)  and  is  a  fat-splitting  enzyme.  It  has  the  power  of  splitting 
the  neutral  fats  of  the  food  by  hydrolysis,  into  fatty  acid  and  glycerol. 
A  typical  reaction  would  be  as  follows: 


Palmitin.  Palmitic  acid.  Glycerol. 

Recent  researches  make  it  probable  that  fats  undergo  saponifica- 
tion  prior  to  their  absorption.  The  fatty  acids  formed  unite  with  the 
alkalis  of  the  pancreatic  juice  and  intestinal  secretion  to  form  soluble 
soaps  which  are  readily  absorbed.  It  was  formerly  believed  that  the 
fats  could  also  be  absorbed  hi  emulsion  —  a  condition  promoted  by  the 
presence  of  the  soluble  soaps.  After  absorption  the  fatty  acids  are 
resynthesized  to  form  neutral  fats  with  glycerol. 

Bloor4  has  reported  experiments  which  "make  it  extremely  probable 

1For  the  literature  see  Kendall  and  Sherman:  Jour.  Am.  Chem.  Soc.,  32,  1087,  1910. 

2  Wohlgemuth  :  Biochem.  Zeit.,  9,  10,  1908;  and  Kendall  and  Sherman:  Jour.  Am.  Chem. 
Soc.,  32,  1087,  1910.  Bierry:  Biochem.  Zeit.,  40,  357,  1912.  Rockwood:  Jour.  Am. 
Chem.  Soc.,  41,  228,  1919. 

3Langworthy  and  Deuel:  Jour.  Biol.  Chem.,  42,  27,  1920. 

4  Bloor:  Jour.  Biol.  Chem.,  15,  105,  1913. 


I Q2  PHYSIOLOGICAL   CHEMISTRY 

that  fats  can  be  absorbed  only  in  water-soluble  form  and  that  saponi- 
fication  is  a  necessary  preliminary  to  absorption."  Petroleum  hydro- 
carbons and  non-saponinable  esters,  e.g.,  wool  fat  (lanolin)  were  un- 
absorbed.  Bloor  further  claims1  that  in  the  absorption  of  fats  there  is 
a  tendency  toward  the  formation  of  a  uniform  chyle  fat,  presumably  the 
characteristic  body  fat  of  the  animal. 

Pancreatic  lipase  is  very  unstable  and  is  easily  rendered  inert  by  the 
action  of  acid>  For  this  reason  it  is  not  possible  to  prepare  an  extract 
having  a  satisfactory  fat-splitting  power  from  a  pancreas  which  has 
been  removed  from  the  organism  for  a  sufficiently  long  time  to  have 
become  acid  in  reaction. 

The  fourth  enzyme  of  the  pancreatic  juice  is  called  pancreatic  rennin. 
It  is  a  milk-coagulating  enzyme  whose  action  is  very  similar  to  that 
of  the  gastric  rennin  found  in  the  gastric  juice.  It  is  supposed  to  show 
its  greatest  activity  at  a  temperature  varying  from  60°  to  65°C. 

PREPARATION  OF  AN  ARTIFICIAL  PANCREATIC  JUICE2 

After  removing  the  fat  from  the  pancreas  of  a  pig  or  sheep,  finely  divide  the 
organ  by  means  of  scissors  and  grind  it  in  a  mortar.  If  convenient,  the  use  of  an 
ordinary  meat  chopper  is  a  very  satisfactory  means  of  preparing  the  pancreas. 

When  finely  divided  as  above  the  pancreas  should  be  placed  in  a  500  c.c. 
flask,  about  150  c.c.  of  30  per  cent  alcohol  added  and  the  flask  and  contents-shaken 
frequently  for  24  hours.  (What  is  the  reaction  of  this  alcoholic  extract  at  the  end 
of  this  period,  and  why?)  Strain  the  alcoholic  extract  through  cheese  cloth, 
filter,  nearly  neutralize  with  potassium  hydroxide  solution  and  then  exactly 
neutralize  it  with  0.5  per  cent  sodium  carbonate. 

Products  of  Tryptic  Digestion 

Introduce  into  a  250  c.c.  flask  20  grams  of  casein,  10  c.c.  of  the  artificial 
pancreatic  juice  prepared  as  described  above  and  100  c.c.  of  i  per  cent  sodium 
carbonate.  Allow  to  digest  at  4O°C.  for  8  to  10  days  with  the  addition  of  a 
few  cubic  centimeters  each  of  chloroform  and  toluene,  the  flask  being  stoppered 
with  cotton.  As  the  chloroform  and  toluene  evaporate  they  must  be  renewed. 
Heat  the  mixture  to  boiling  and  at  the  boiling-point  add  acetic  acid  drop  by  drop 
until  the  mixture  is  acid  in  reaction.  Cool  and  filter. 

To  five  c.c.  of  the  filtrate  add  bromine  water  drop  by  drop.  Note  the  develop- 
ment of  pink  color  which  disappears  hi  the  presence  of  an  excess  of  the  reagent. 
This  reaction  indicates  the  presence  of  tryptophane.3 

To  another  5  c.c.  portion  of  the  filtrate  add  10  drops  of  concentrated  sulphuric 
acid  and  10  c.c.  of  a  10  per  cent  solution  of  mercuric  sulphate  hi  5  per  cent  sul- 
phuric acid.  After  mixing  and  allowing  to  stand  for  a  few  minutes  filter  off 
the  yellow  precipitate  which  forms.  This  is  a  mercury  compound  of  tryptophane.  * 

'Bloor:  Jour.  Biol.  Chem.,  16,  517,  1914. 

*  For  other  methods  of  preparation  see  Karl  Mays:  Zeitschrift  fur  physiologischc  Chemie, 
38,  428,  1903. 

3Kurajeff:  Zeit.  physiol.  Chem.,  36,  501,  1898-99. 

4  It  has  been  claimed  that  a  similar  yellow  precipitate  forms  in  the  presence  of  tyrosine. 
cystine  and  polypeptides.  For  quantitative  estimation  of  tryptophane  see  Homer:  Jour, 
Biol.  Chem.,  22,  369,  1915. 


PANCREATIC   DIGESTION  1 93 

Filter  off  the  precipitate  reserving  the  filtrate  and  wash  the  precipitate  on  the 
filter  paper  thoroughly  with  several  small  portions  of  water. 

To  small  portions  of  the  precipitate  apply  the  Hopkins-Cole,  xanthoproteic, 
and  Millon  tests.  Tryptophane  gives  a  positive  reaction  with  the  first  two  of 
these  tests  being  responsible  for  the  Hopkins-Cole  reaction  as  applied  to  protein 
(see  Chapter  V). 

Test  portions  of  the  filtrate  from  the  mercuric  precipitate  by  the  Hopkins- 
Cole,  xanthoproteic,  and  Millon  reactions.  Tyrosine  responds  to  the  latter  two 
tests. 

To  the  remainder  of  the  filtrate  add  a  few  drops  of  ammonia1  and  evaporate 
to  a  volume  of  10  to  20  c.c.  using  at  first  a  free  flame  and  completing  the  evapora- 
tion on  a  water-bath.  Transfer  to  a  beaker  and  allow  to  stand  for  i  or  2  days. 
Examine  microscopically  the  crystals  which  separate  out.  Tyrosine  crystallizes 
in  sheaves  of  needles  (see  Fig.  25).  Leucine  forms  small  rosettes.  Apply 
Morner's  reaction  for  tyrosine  (see  p.  85). 


GENERAL  EXPERIMENTS  ON  PANCREATIC  DIGESTION 

EXPERIMENTS  ON  TRYPSIN2 

1.  The  Most  Favorable  Reaction  for  Tryptic  Digestion. — Prepare  seven  tubes 
as  follows : 

(a)  2-3  c.c.  of  neutral  pancreatic  extract  +  2-3  c.c.  of  water. 

(b)  2-3  c.c.  of  neutral  pancreatic  extract  +  2-3  c.c.  of  i  per  cent  sodium  car- 
bonate. 

(c)  2-3  c.c.  of  neutral  pancreatic  extract  -f  2-3  c.c.  of  0.5  per  cent  sodium 
carbonate. 

(d)  2-3  c.c.  of  neutral  pancreatic  extract  +  2-3  c.c.  of  0.2  per  cent  hydro- 
chloric acid. 

(e)  2-3  c.c.  of  neutral  pancreatic  extract  +  2-3  c.c.  of  0.2  per  cent  combined 
hydrochloric  acid. 

(f)  2-3  c.c.  of  neutral  pancreatic  extract  -f  2-3  c.c.  of  0.4  per  cent  boric  acid. 

(g)  2-3  c.c.  of  neutral  pancreatic  extract  +  2-3  c.c.  of  0.4  per  cent  acetic  acid. 
Add  a  small  piece  of  fibrin3  to  the  contents  of  each  tube  and  keep  them  at  4O°C. 

noting  the  progress  of  digestion.  In  which  tube  do  we  find  the  most  satisfactory 
digestion,  and  why?  How  do  the  indications  of  the  digestion  of  fibrin  by  trypsin 
differ  from  the  indications  of  the  digestion  of  fibrin  by  pepsin? 

2.  The  Most  Favorable  Temperature. — (For  this  and  the  following  series  of 
experiments  under  tryptic  digestion  use  the  neutral  extract  plus  an  equal  volume 
of  0.5  per  cent  sodium  carbonate.)    In  each  of  four  tubes  place  5  c.c.  of  alkaline 
pancreatic  extract.    Immerse  one  tube  in  cold  water  from  the  faucet,  keep  a 
second  at  room  temperature  and  place  a  third  in  the  incubator  or  water-bath  at 
4O°C.    Boil  the  contents  of  the  fourth  for  a  few  moments,  then  cool  and  also  keep 

1  If  the  solution  is  alkaline  in  reaction,  while  it  is  being  concentrated,  the  amino  acids 
will  be  broken  down  and  ammonia  will  be  liberated. 

2  For  these  experiments  as  well  as  for  those  on  the  other  pancreatic  enzymes  commer- 
cial preparations  of  trypsin  and  pancreatin  may  be  employed. 

3  Congo  red  fibrin  may  be  used  in  this  and  the  following  tests  on  tryptic  digestion.     If 
used  the  experiments  should  be  made  at  room  temperature.     For  preparation  of  this 
fibrin  see  Chapter  I. 

13 


IQ4  PHYSIOLOGICAL  CHEMISTRY 

it  at  40°C.  Into  each  tube  introduce  a  small  piece  of  fibrin  and  note  the  progress 
of  digestion.  In  which  tube  does  the  most  rapid  digestion  occur?  What  is  the 
reason? 

3.  Influence  of  Bile. — Prepare  three  tubes  as  follows : 

(a)  5  c.c.  of  pancreatic  extract  -f-  0.5-1  c.c.  of  bile. 

(b)  5  c.c.  of  pancreatic  extract  +  5  c.c.  of  bile. 

(c)  5  c.c.  of  pancreatic  extract. 

Introduce  into  each  tube  a  small  piece  of  fibrin  and^keep  them  at  4O°C. 
Shake  the  tubes  frequently  and  note  the  progress  of  digestion.  Does  the  pres- 
ence of  bile  retard  tryptic  digestion?  How  do  these  results  agree  with  those 
obtained  under  gastric  digestion? 

4.  Quantitative  Determination  of  Tryptic  Activity.1 — Gross*  Method. — This 
method  is  based  upon  the  principle  that  faintly  alkaline  solutions  of  casein  are 
precipitated  upon  the  addition  of  dilute  (i  per  cent)  acetic  acid  whereas  its  digestion 
products  are  not  so  precipitated.  The  method  follows :  Prepare  a  series  of  tubes 
each  containing  10  c.c.  of  a  o.i  per  cent  solution  of  pure,  fat-free  casein,2  which 
has  been  heated  to  a  temperature  of  4O°C.  Add  to  the  contents  of  the  series  of 
tubes  increasing  amounts  of  the  trypsin  solution  under  examination,3  and  place 
them  at  4O°C.  for  fifteen  minutes.  At  the  end  of  this  time  remove  the  tubes  and 
acidify  the  contents  of  each  with  a  few  drops  of  dilute  (i  per  cent)  acetic  acid. 
The  tubes  in  which  the  casein  is  completely  digested  will  remain  clear  when 
acidified,  while  those  tubes  which  contain  undigested  casein  will  become  more 
or  less  turbid  under  these  conditions.  Select  the  first  tube  in  the  series  which 
exhibits  no  turbidity  upon  acidification,  thus  indicating  complete  digestion  of 
the  casein,  and  calculate  the  tryptic  activity  of  the  enzyme  solution  under 
examination. 

Calculation. — The  unit  of  tryptic  activity  is  an  expression  of  the  power  of  i 
c.c.  of  the  fluid  under  examination  exerted  for  a  period  of  fifteen  minutes  on  10 
c.c.  of  a  o.i  per  cent  casein  solution.  For  example,  if  0.5  c.c.  of  a  trypsin  solu- 
tion completely  digests  10  c.c.  of  a  o.i  per  cent  solution  of  casein  in  fifteen 
minutes,  the  activity  of  that  solution  would  be  expressed  as  follows : 

Tryptic  activity  =  1-1-0.5=2. 

Such  a  trypsin  solution  would  be  said  to  possess  an  activity  of  2.  If  0.3  c.c. 
of  the  trypsin  solution  had  been  required  the  solution  would  be  said  to  possess  an 
activity  of  3.3 ;  i.e.,  i  -1-0.3  =3-3' 

EXPERIMENTS  ON  PANCREATIC  AMYLASE 

i.  The  Most  Favorable  Reaction. — Prepare  four  tubes  as  follows' 

(a)  i  c.c.  of  neutral  pancreatic  extract+i  c.c.  of  starch  paste +2  c.c.  of 
water. 

(b)  i  c.c.  of  neutral  pancreatic  extract+i   c.c.  of  starch  paste+2  c.c.   of 
i  per  cent  sodium  carbonate. 

1  For  a  discussion  of  Spencer's  method  for  the  quantitative  determination  of  trypsin 
in  stomach  contents  see  chapter  on  Gastric  Analysis. 

2  Made  by  dissolving  i  gram  of  Gru  bier's  casein  in  a  liter  of  o.i  per  cent  sodium  car- 
bonate.    A  little  chloroform  may  be  added'to  prevent  bacterial  action. 

3  The  amount  of  solution  used  may  vary  from  o.i-i  c.c.     The  measurements  may 
conveniently  be  made  by  means  of  a  i  c.c.  graduated  pipette. 


PANCREATIC   DIGESTION  195 

(c)  i  c.c.  of  neutral  pancreatic  extract -fi  c.c.  of  starch  paste +2  c.c.  of 
0.5  per  cent  sodium  carbonate. 

(d)  i  c.c.  of  neutral  pancreatic  extract -fi  c.c.  of  starch  paste +2  c.c.  of 
0.2  per  cent  hydrochloric  acid. 

Shake  each  tube  thoroughly  and  place  them  in  the  incubator  or  water-bath 
at  4O°C.  At  the  end  of  a  half -hour  divide  the  contents  of  each  tube  into  two  parts 
and  test  one  part  by  the  iodine  test  and  the  other  part  by  Fehling's  test.  Where 
do  you  find  the  most  satisfactory  digestion?  How  do  the  results  compare  with 
those  obtained  from  Experiment  i  under  Trypsin,  page  193? 

2.  The  Most  Favorable  Temperature. — (For  this  and  the  following  series  of 
experiments  upon  pancreatic  amylase  use  the  neutral  extract  plus  an  equal  vol- 
ume of  0.5  per  cent  sodium  carbonate.)    In  each  of  four  tubes  place  2-3  c.c.  of 
alkaline  pancreatic  extract.    Immerse  one  tube  hi  cold  water  from  the  faucet, 
keep  a  second  at  room  temperature,  and  place  a  third  on  the  water-bath  at  4O°C. 
Boil  the  contents  of  the  fourth  for  a  few  moments,  then  cool  and  also  keep  it  at 
40°C.    Into  each  tube  introduce  2-3  c.c.  of  starch  paste  and  note  the  progress  of 
digestion.    At  the  end  of  one-half  hour  divide  the  contents  of  each  tube  into  two 
parts  and  test  one  part  by  the  iodine  test  and  the  other  part  by  Fehling's  test. 
In  which  tube  do  you  find  the  most  satisfactory  digestion?    How  does  this  result 
compare  with  the  result  obtained  in  the  similar  series  of  experiments  under 
Trypsin  (see  page  193)? 

3.  Influence  of  Bile. — Prepare  three  tubes  as  follows: 

(a)  2-3  c.c.  of  pancreatic  extract +2-3  c.c.  of  starch  paste +0.5-1  c.c.  of 
bile. 

(b)  2-3  c.c.  of  pancreatic  extract +2-3  jc.c.  of  starch  paste +5  c.c.  of  bile. 

(c)  2-3  c.c.  of  pancreatic  extract+2-3  c.c.  of  starch  paste. 

Shake  the  tubes  thoroughly  and  place  them  hi  the  incubator  or  water-bath 
at  40°C.  Note  the  progress  of  digestion  frequently  and  at  the  end  of  a  half -hour 
divide  the  contents  of  each  tube  into  two  parts  and  test  one  part  by  the  iodine 
test  and  the  other  part  by  Fehling's  test.  What  are  your  conclusions  regarding 
the  influence  of  bile  upon  the  action  of  pancreatic  amylase? 

4.  Digestion  of  Dry  Starch. — To  a  little  dry  starch  in  a  test-tube  add  about 
5  c.c.  of  pancreatic  extract  and  place  the  tube  hi  the  incubator  or  water-bath  at 
4O°C.    At  the  end  of  a  half -hour  filter  and  test  separate  portions  of  the  filtrate 
by  the  iodine  and  Fehling  tests.    What  do  you  conclude  regarding  the  action  of 
pancreatic  amylase  upon  dry  starch?    Compare  this  result  with  that  obtained  in 
the  similar  experiment  under  Salivary  Digestion  (page  59). 

5.  Digestion  of  Inulin. — To  5  c.c.  of  inulin  solution  in  a  test-tube  add  10  drops 
of  pancreatic  extract  and  place  the  tube  in  the  incubator  or  water-bath  at  40° C. 
After  one-half  hour  test  the  solution  by  Fehling's  test.1    Is  any  reducing  substance 
present?    What  do  you  conclude  regarding  the  digestion  of  inulin  by  pancreatic 
amylase? 

6.  Quantitative    Determination    of    Amylolytic    Activity.— Wohlgemuth's 
Method.2    Arrange  a  series  of  test-tubes  with  diminishing  quantities  of  the 
enzyme  solution  under  examination,  introduce  into  each  tube  5  c.c.  of  i  per  cent 

1  If  the  inulin  solution  gives  a  reduction  before  being  acted  upon  by  the  pancreatic  juice 
it  will  be  necessary  to  determine  the  extent  of  the  original  reduction  by  means  of  a  "check" 
test  (see  p.  46). 

•Wohlgemuth:  Biochemische  Zeitschrift,  9,  i,  iQo8. 


196  PHYSIOLOGICAL   CHEMISTRY 

solution  of  soluble  starch1  and  place  each  tube  at  once  hi  a  bath  of  ice-water.2 
When  all  the  tubes  have  been  prepared  in  this  way  and  placed  in  the  ice-water 
bath  they  are  transferred  to  a  water-bath  or  incubator  and  kept  at  38°C.  for  from 
30  minutes  to  an  hour.3  At  the  end  of  this  digestion  period  the  tubes  are  again 
removed  to  the  bath  of  ice-water  in  order  that  the  action  of  the  enzyme  may 
be  stopped. 

Dilute  the  contents  of  each  tube,  to  within  about  1/2  inch  of  the  top,  with 
water,  add  one  drop  of  a  N/io  solution  of  iodine  and  shake  the  tube  and  contents 
thoroughly.  A  series  of  colors  ranging  from  dark  blue  through  bluish  violet  and 
reddish  yellow  to  yellow,  will  be  formed. 4  The  dark  blue  color  shows  the  presence 
of  unchanged  starch,  the  bluish-violet  indicates  a  mixture  of  starch  and  erythro- 
dextrin,  whereas  the  reddish-yellow  signifies  that  erythrodextrin  and  maltose  are 
present  and  the  yellow  solution  denotes  the  complete  transformation  of  starch 
into  maltose.  Examine  the  tubes  carefully  before  a  white  background  and  select 
the  last  tube  in  the  series  which  shows  the  entire  absence  of  all  blue  color,  thus 
indicating  that  the  starch  has  been  completely  transformed  into  dextrins  and 
sugar.  In  case  of  indecision  between  two  tubes,  add  an  extra  drop  of  the  iodine 
solution,  and  observe  them  again,  after  shaking. 

Calculation. — The  amylolytic  activity5  of  a  given  solution  is  expressed  in  terms 
of  the  activity  of  i  c.c.  of  such  a  solution.  For  example,  if  it  is  found  that  0.02 
c.c.  of  an  amylolytic  solution,  acting  at  38°C.,  completely  transformed  the  starch 
in  5  c.c.  of  a  i  per  cent  starch  solution  in  30  minutes,  the  amylolytic  activity  of 
such  a  solution  would  be  expressed  as  follows : 

rC=2so 

This  indicates  that  i  c.c.  of  the  solution  under  examination  possesses  the  power 
of  completely  digesting  250  c.c.  of  i  per  cent  starch  solution  in  30  minutes  at 
38°C. 

Wohlgemuth  has  suggested  a  slight  alteration  in  the  above  procedure  for  use 
in  the  determination  of  tne  amylase  content  of  thejfeces.6  A  modification  of  the 
Wohlgemuth  procedure7  for  this  purpose  is  given  in  the  chapter  on  Feces. 

EXPERIMENTS  ON  PANCREATIC  LIPASE 

i .  Influence  of  Bile  on  Action  of  Lipase. — Prepare  five  test-tubes  as  follows : 
(a)  5  c.c.  neutral  pancreatic  extract  -f  0.5  c.c.  olive  oil  -f  4.5  c.c.  water. 

1  Kahlbaum's  soluble  starch  is  satisfactory.     In  preparing  the  i  per  cent  solution,  the 
weighed  starch  powder  should  be  dissolved  in  cold  distilled  water  in  a  casserole  and  stirred 
until  a  homogeneous  suspension  is  obtained.     The  mixture  should  then  be  heated,  with  con- 
stant stirring,  until  it  is  clear.     This  ordinarily  takes  about  8-10  minutes.     A  slightly 
opaque  solution  is  thus  obtained  which  should  be  cooled  and  made  up  to  the  proper  volume 
before  using. 

2  Ordinarily  a  series  of  six  tubes  is  satisfactory,  the  volumes  of  the  enzyme  solution  used 
ranging  from  *  c.c.  to  o.i  c.c.  and  the  measurements  being  made  by  means  of  a  i  c.c.  gradu- 
ated pipette.    All  tubes  should  contain  the  same  volume  of  material.    To  accomplish 
this  add  appropriate  amounts  of  distilled  water  to  tubes  receiving  less  than  i  c.c.  of  enzyme 
solution.     Each  tube  should  be  placed  in  the  ice-water  bath  as  soon  as  the  starch  solution 
is  introduced.    It  will  be  found  convenient  to  use  a  small  wire  basket  to  hold  the  tubes. 

3  Longer  digestion  periods  may  be  used  where  it  is  deemed  advisable.    If  exceedingly 
weak  solutions  are  being  investigated,  it  may  be  most  satisfactory  to  permit  the  digestion  to 
extend  over  a  period  of  24  hours. 

4  See  p.  55. 

6 Designated  by  "D"  the  first  letter  of  "diastatic." 

8  Wohlgemuth:  Berliner  klinische  Wochenschrift,  47,  92,  1910. 

7  Hawk:  Archives  of  Internal  Medicine,  8,  552,  1911. 


PANCREATIC   DIGESTION  197 

(b)  0.5  c.c.  olive  oil  +  9.5  c  c.  water. 

(c)  0.5  c.c.  olive  oil  +  8.5  c.c.  water  +  i  c.c.  bile. 

(d)  5  c.c.  neutral  pancreatic  extract  -f-  0.5  c.c.  olive  oil  +  3.5  c.c.  water  + 

i  c.c.  bile. 

(e)  5  c.c.  neutral  pancreatic  extract  +  3.5  c.c.  water  +  i  c.c.  bile. 

Shake  the  tubes  thoroughly,  add  a  drop  of  toluene  to  each  and  place  them 
in  an  incubator  or  water-bath  at  40°  for  24  hours.  At  the  end  of  this  period 
add  a  drop  of  phenolphthalein  to  each  tube  and  titrate  with  N/2O  NaOH  to  a 
permanent  pink  color.  Shake  the  tube  during  the  titration.  Record  the 
amount  of  N/2O  alkali  necessary  to  neutralize  the  contents  of  each  tube.  Which 
tube  required  the  most?  Why? 

2.  "Litmus-milk"  Test. — Into  each  of  two  test-tubes  introduce  10  c.c.  of  milk 
and  a  small  amount  of  litmus  solution.1    To  the  contents  of  one  tube  add  3  c.c. 
of  neutral  pancreatic  extract2  and  to  the  contents  of  the  other  tube  add  3  c.c.  of 
water  or  of  boiled  neutral  pancreatic  extract.    Keep  the  tubes  at  4O°C.  and  note 
any  changes  which  may  occur.    What  is  the  result  and  how  do  you  explain  it? 

3.  Copper  Soap  Test  for  Lipase. — Prepare  a  2  :ioo  agar-agar  solution,  mix 
with  an  equal  volume  of  5  :ioo  starch  paste,  incorporate  in  this  mass  about 
1/40  of  its  volume  of  the  neutral  fat  desired  (butter,  lard,  etc.),  heat  with  constant 
agitation  until  a  homogeneous  emulsion  is  produced,  pour  into  a  Petri  dish,  and 
cool  rapidly.    Distribute  on  the  surface  of  the  solidified  mass  with  a  fine  pipet 
small  drops  of  the  liquid  to  be  tested,  keep  i  hour  at  38°,  pour  a  saturated  aqueous 
CuSO4  solution  over  the  surface,  allow  to  stand  10  minutes,  and  rinse  with 
H2O.     The  presence  of  lipase  is  shown  by  the  appearance  of  beautiful  bluish- 
green  spots.     These  are  copper  soap.    The  addition  of  the  starch,  which  is  not 
indispensable,  produces  a  rather  white  opaque  background  against  which  the 
spots    appear    very  distinct.     (Carnot   and   Mauban — Compt.    rend.    Soc.    Biol. 
81,  98,  1918,  Chemical  Abstracts,  13,  457,  1919). 

4.  Ethyl  Butyrate  Test. — Into  each  of  two  test-tubes  introduce  4  c.c.  of  water, 
2  c.c.  of  ethyl  butyrate,  C3H7COO.C2H5,  and  a  small  amount  of  litmus  powder. 
To  the  contents  of  one  tube  add  4  c.c.  of  neutral  pancreatic  extract  and  to  the 
contents  of  the  other  tube  add  4  c.c.  of  water  or  of  boiled  neutral  pancreatic  ex- 
tract.   Keep  the  tubes  at  4O°C.  and  observe  any  change  which  may  occur. 
What  is  the  result  and  how  do  you  explain  it?    Write  the  equation  for  the  reac- 
tion which  has  taken  place. 

EXPERIMENTS  ON  PANCREATIC  RENNIN 

Prepare  four  test-tubes  as  follows : 

(a)  5  c.c.  of  milk  -f  10  drops  of  neutral  pancreatic  extract. 

(b)  5  c.c.  of  milk  +  20  drops  of  neutral  pancreatic  extract. 

(c)  5  c.c.  of  milk  +  10  drops  of  alkaline  pancreatic  extract. 

(d)  5  c.c.  of  milk  -f-  20  drops  of  alkaline  pancreatic  -extract. 

Place  the  tubes  at  6o°-6s°C.  for  a  half  hour  without  shaking.  Note  the 
formation  of  a  clot.3  How  does  the  action  of  pancreatic  rennin  compare  with  the 
action  of  the  gastric  rennin? 

litmus-milk  powder  may  be  used  if  desired.  To  prepare  it  add  i  part  of  powdered 
litmus  to  50  parts  of  dried  milk  powder.  For  use  in  testing,  i  part  of  powdered  litmus- 
milk  may  be  added  to  9. parts  of  water  (Hamilton:  Jour.  Bact.,  6,  43,  1921). 

2  Commercial  pancreatin  may  be  used  in  this  test  if  desired. 

3  This  reaction  will  not  always  succeed,  owing  to  conditions  which  are  not  well  under- 
stood. 


CHAPTER  XI 
INTESTINAL  DIGESTION 

Strictly  speaking,  all  digestive  processes  which  take  place  in  the 
intestine  may  be  classed  under  Intestinal  Digestion.  However,  we  will 
consider  under  Intestinal  Digestion  only  those  digestive  processes 
which  are  brought  about  by  enzymes  which  have  their  origin  in  the  intes- 
tine. The  activities  of  those  enzymes  which  originate  in  the  pancreas 
we  have  considered  in  Chapter  X  under  Pancreatic  Digestion. 

It  has  been  shown1  that  the  reaction  of  the  small  intestine  may 
vary  from  acid  to  alkaline  and  is  influenced  by  the  state  of  digestion. 

The  enzymes  of  the  intestinal  juice  (succus  entericus)  are  of  great 
importance  to  the  animal  organism.  These  enzymes  include  erepsin, 
sucrase,  maltase,  lactase,  nucleases,  and  enterokinase. 

Erepsin  is  a  proteolytic  enzyme  which  has  the  property  of  acting 
upon  the  proteoses,  peptones,  and  pep  tides  which  are  formed  through  the 
action  of  trypsin,  and  further  splitting  them  into  ammo-acids.  Erepsin 
has  no  power  of  digesting  any  native  proteins  except  caseinogen,  his- 
tones,  and  protamines.  It  possesses  its  greatest  activity  in  an  alkaline 
solution,  although  it  is  slightly  active  in  acid  solution.  An  extract  of  the 
intestinal  erepsin  may  be  prepared  by  treating  the  finely  divided  intes- 
tine of  a  cat,  dog,  or  pig  with  toluene  or  chloroform- water  and  per- 
mitting the  mixture  to  stand  with  occasional  shaking  for  24-72  hours. 
Enzymes  similar  to  erepsin  occur  in  various  tissues  of  the  organism. 

In  cases  of  gastric  cancer  a  pep  tide-splitting  enzyme  is  claimed  to 
be  present  in  the  stomach  contents.  The  glycyl-tryptophane  test  is 
sometimes  used  for  its  detection.  Some  investigators  claim  that  the 
peptide-splitting  power  of  gastric  juice  in  cancer  is  generally  due  to  the 
regurgitation  of  trypsin  or  erepsin  from  the  intestine  or  to  the  presence 
in  the  gastric  contents  of  swallowed  saliva  which  possesses  peptolytic 
power.  The  peptide-splitting  power  of  saliva  may  be  due  to  a  specific 
enzyme  or  to  the  presence  of  bacteria  (see  Glycyl-tryptophane  Reaction, 
page  202). 

The  three  invertases  sucrase,  maltase,  and  lactase  are  also  important 
enzymes  of  the  intestinal  mucosa.  The  sucrase  acts  upon  sucrose 
and  inverts  it  with  the  formation  of  invert  sugar  (glucose  and  fructose). 
Some  investigators  claim  that  sucrase  is  also  present  in  saliva  and 
gastric  juice.  It  probably  does  not  exist  normally  in  either  of  these 

lLong  and  Fenger:  Jour.  Am.  Chem.  Soc.,  39,  1278,  1917. 

198 


INTESTINAL  DIGESTION  1 99 

digestive  juices,  however,  and  if  found  owes  its  presence  to  the  excretory 
processes  of  certain  bacteria.  Sucrases  may  also  be  obtained  from 
several  vegetable  sources.  For  investigational  purposes  it  is  ordinarily 
obtained  from  yeast  (see  page  14).  It  exhibits  its  greatest  activity 
in  the  presence  of  a  slight  acidity,  but  if  the  acidity  be  increased  to  any 
extent  the  reaction  is  inhibited. 

'  Lactase  is  an  enzyme  which  inverts  lactose  with  the  consequent 
formation  of  glucose  and  galactose.  Its  action  is  entirely  analogous, 
in  type,  to  that  of  sucrase.  It  has  apparently  been  proven  that  lactase 
occurs  in  the  intestinal  mucosa  of  the  young  of  all  animals  which  suckle 
their  offspring.1  It  may  also  occur  in  the  intestinal  mucosa  of  certain 
adult  animals  if  such  animals  be  maintained  upon  a  ration  containing 
more  or  less  lactose.  Fischer  and  Armstrong  have  demonstrated  the 
reversible  action2  of  lactase. 

Maltase  possesses  the  power  of  splitting  maltose,  the  end-product 
of  the  digestion  of  starch,  into  glucose.  It  was  first  discovered  in  the 
urine  and  shortly  after  this  time  its  presence  was  noted  in  the  small 
intestine  and  the  saliva.  Corn  is  sometimes  used  as  the  medium  for 
the  preparation  of  the  enzyme  for  experimental  purposes.  It  occurs 
in  corn  in  a  very  active  state.  It  was  in  connection  with  maltase  that 
the  principles  of  the  "reversibility  of  enzyme  action"  were  first 
demonstrated. 

Enterokinase  possesses  the  power  of  "activating"  trypsinogen  see 
Chapters  I  and  X).  In  other  words,  trypsinogen  as  formed  by  the 
pancreas  has  no  proteolytic  power,  but  when  this  inactive  trypsino- 
gen reaches  the  intestine  and  comes  into  contact  with  enterokinase  the 
latter  transforms  it  into  active  trypsin.  Enterokinase  is  not  always 
present  in  the  intestinal  juice  since  it  is  secreted  only  after  the  pan- 
creatic juice  reaches  the  intestine.  It  resembles  the  enzymes  in  that 
its  activity  is  destroyed  by  heat,  but  differs  materially  from  this  class 
of  bodies  in  that  a  certain  quantity  is  capable  of  activating  only  a 
definite  quantity  of  trypsinogen.  It  is,  however,  generally  classified 
as  an  enzyme.  Enterokinase  has  been  detected  in  the  higher  animals, 
and  a  kinase  possessing  similar  properties  has  been  shown  to  be  present 
in  bacteria,  fungi,  impure  fibrin,  lymph  glands,  and  snake-venom. 

The  intestinal  juice  and  the  epithelium  of  the  intestinal  wall  con- 
tain enzymes  capable  of  hydrolyzing  nucleic  acids  and  as  these  acids 
are  not  acted  upon  by  the  gastric  juice  and  probably  not  to  any  great 
extent  by  pure  pancreatic  juice,  the  intestine  apparently  plays  the  chief 
r61e  in  decomposition  or  digestion  of  these  substances.  At  least  two 

1  Mendel  and  Mitchell:  American  Journal  of  Physiology,  20,  81,  1907. 
8  See  p.  8. 


2OO  PHYSIOLOGICAL   CHEMISTRY 

enzymes  take  part  in  this  digestion  process,  one  decomposing  the 
nucleic  acid  with  formation  of  simple  nucleotides  containing  a  single 
radical  each  of  phosphoric  acid,  carbohydrate  and  base  (see  chapter 
on  Nucleic  Acids).  This  enzyme  may  be  called  nucleicacidase.  An- 
other enzyme  present  in  the  intestine  and  intestinal  juice  decomposes 
these  nucleotides  with  the  liberation  of  phosphoric  acid.  This  enzyme 
may  be  called  nucleotidase  or  phosphonuclease.  The  intestinal  mucosa 
also  decomposes  many  other  organic  phosphorus  compounds  with  libera- 
tion of  their  phosphoric  acid.1  Thus  glycero-phosphoric  acid  and 
hexbse-phosphoric  acid  as  well  as  phosphoproteins  are  split  in  a  similar 
manner,  the  phosphoric  acid  they  contain  thus  being  absorbed  in  the 
free  form. 

GENERAL  EXPERIMENTS  ON  INTESTINAL  DIGESTION 

Demonstration  of  Enterokinase. — Trypsinogen  may  be  activated 
by  enterokinase.  This  activation  occurs  normally  in  the  intestine. 
Calcium  salts  also  bring  about  a  similar  activation  of  the  trypsinogen. 

Procedure. — Prepare  an  extract  of  trypsinogen  by  grinding  10  grams  of  the 
fresh,  fat-free  pancreas  of  the  pig  with  a  little  sand.  Gradually  add  100  c.c. 
of  water  during  the  grinding  process.  Strain  through  cheese  cloth. 

Prepare  an  extract  of  enterokinase  by  grinding  5  grams  of  fresh,  fat-free 
duodenal  mucosa2  of  the  pig  with  a  little  sand.  Gradually  add  50  c.c.  of  water 
during  the  grinding  process.  Strain  through  cheese  cloth. 

Prepare  the  following  series  of  tubes : 

(a)  10  c.c.  pancreas  extract +5  c.c.  water. 

(b)  10  c.c.  pancreas  extract+5  c.c.  duodenal  extract. 

(c)  5  c.c.  duodenal  extract+io  c.c.  water. 

(d)  10  c.c.  pancreas  extract  +5  c.c.  duodenal  extract. 

(e)  10  c.c.  pancreas  extract+5  c.c.  duodenal  extract  (boiled). 

(f)  10  c.c.  pancreas  extract+5  c.c.  of  4  per  cent  calcium  chloride. 

Boil  the  contents  of  tube  (d)  for  five  minutes  and  cool  to  4O°C.  Keep  all  six  tubes 
at  40°C.  for  20  minutes. 

To  each  tube  add  5  c.c.  of  10  per  cent  sodium  carbonate  and  mix  the  contents 
thoroughly  and  immediately.  Introduce  into  each  tube  the  same  quantity  (size 
of  a  pea)  of  fresh  fibrin.  Shake  the  tubes  and  place  them  at  4O°C.  Observe  the 
tubes  frequently  for  one  hour  to  note  digestive  changes.  Tubes  (b)  and  (f) 
should  show  most  rapid  digestion.  Why? 

EXPERIMENTS  ON  INTESTINAL  NUCLEASES. 

i.  Preparation  of  Intestinal  Extract.— Wash  thoroughly  100  grams  of  pig's 
intestine  and  run  through  a  meat  chopper  several  times.  Introduce  into  a  500 
c.c.  mixing  cylinder  and  add  normal  salt  solution  to  make  500  c.c.  Allow  to 

lPlimmer:  Biochem.  /.,  7,  43,  1913. 

2  The  dried  mucosa  may  be  substituted  if  desired. 


INTESTINAL   DIGESTION  2OI 

stand  for  6-24  hours  at  room  temperature,  shaking  occasionally,  toluene  being 
added  as  a  preservative.  Strain  and  filter. 

2.  Demonstration  of  Intestinal  Nucleases. — Prepare  a  2  per  cent  solution 
of  yeast  nucleic  acid  put  in  solution  with  the  aid  of  just  sufficient  NaOH  solution 
to  make  the  resulting  mixture  neutral  to  litmus.  To  each  of  two  large  test-tubes 
add  20  c.c.  of  the  intestinal  extract  prepared  as  above.  Boil  one  for  one  to  two 
minutes.  To  each  tube  then  add  10  c.c.  of  the  2  per  cent  nucleic  acid  solution. 
Add  2-3  c.c.  each  of  toluene  and  chloroform  to  each  mixture.  Keep  at  38°C. 
for  24  hours. 

Heat  the  tubes  to  boiling  in  a  water-bath  to  coagulate  protein.  Add  5  c.c.  of 
5  per  cent  HCt  and  allow  to  stand  for  one  hour.  This  precipitates  any  unchanged 
nucleic  acid.  Filter  and  take  aliquots  of  the  filtrate  (about  20  c.c.).  Precipitate 
the  phosphate  from  each  mixture  by  adding  5  c.c.  of  magnesia  mixture  and  5  c.c. 
of  ammonia.  Allow  to  stand  over  night.  A  heavy  precipitate  of  magnesium 
ammonium  phosphate  should  be  found  hi  the  test  e^xperiment  indicating  that  the 
phosphoric  acid  of  the  nucleic  acid  had  been  liberated  by  the  nucleotidase  of  the 
intestinal  extract.  The  control  should  show  only  a  slight  precipitate. 

If  desired  the  phosphorus  of  the  precipitates  may  be  determined  quantitatively 
by  dissolving  hi  2  per  cent  HNO3,  precipitating  as  the  phosphomolybdate  and 
determining  volumetrically  according  to  the  Neumann  procedure  (see  p.  570). 


EXPERIMENTS  ON  EREPSIN 

1.  Preparation  of  Erepsin. — Grind  the  mucous  membrane  of  the  small  intes- 
tine of  a  cat,  dog,  or  pig  with  sand  hi  a  mortar.    Treat  the  finely  divided  mem- 
brane with  toluene  or  chloroform-water  and  permit  the  mixture  to  stand,  with 
occasional  shaking,  for  24-72  hours.1    Filter  the  extract  thus  prepared  through 
cotton  and  use  the  filtrate  in  the  following  experiment. 

2.  Demonstration  of  Erepsin. — To  about  5  c.c.  of  a  i  per  cent  solution  of 
Witte's  peptone  in  a  test-tube  add  about  i  c.c.  of  the  erepsin  extract  prepared  as 
described  above  and  make  the  mixture  slightly  alkaline  (o.i  per  cent)  with  sodium 
carbonate.    Prepare  a  second  tube  containing  a  like  amount  of  peptone  solution 
but  boil  the  erepsin  extract  before  introducing  it.    Place  the  two  tubes  at  38°C. 
for  two  to  three  days.    At  the  end  of  that  period  heat  the  contents  of  each  tube 
to  boiling,  filter  and  try  the  biuret  test  on  each  filtrate.    In  making  these  tests 
care  should  be  taken  to  use  like  amounts  of  filtrate,  potassium  hydroxide  and 
copper  sulphate  in  each  test  in  order  that  the  drawing  of  correct  conclusions  may 
be  facilitated.    The  contents  of  the  tube  which  contained  the  boiled  extract 
should  show  a  deep  pink  color  with  the  biuret  test,  due  to  the  peptone  still  present. 
On  the  other  hand,  the  biuret  test  upon  the  contents  of  the  tube  containing  the 
unboiled  extract  should  be  negative  or  exhibit,  at  the  most,  a  faint  pink  or  blue 
color,  signifying  that  the  peptone,  through  the  influence  of  the  erepsin,  has  been 
transformed,  in  great  part  at  least,  into  amino-acids  which  do  not  respond  to  the 
biuret  test.2 

1  The  enzyme  may  also  be  extracted  by  means  of  glycerol  or  alkaline  "  physiological"  salt 
solution  if  desired. 

2  Strictly  speaking,  this  erepsin  demonstration  is  not  adequate  unless  a  control  test 
is  made  with  native  protein  (except  casein,  histones  and  protamines)  to  show  that  the 
extract  is  trypsin-free  and  digests  peptone  but  not  native  protein. 


202  PHYSIOLOGICAL  CHEMISTRY 

3.  The  Glycyl-tryptophane  Reaction. — The  dipeptide  glycyl-tryptophane1 
may  be  used  in  place  of  the  peptone  solution  for  the  demonstration  of  erepsin. 
It  is  claimed  to  be  of  service  in  the  diagnosis  of  gastric  cancer.  It  is  claimed  that 
a  peptide-splitting  enzyme  (erepsin)  is  present  in  the  stomach  contents  of  indi- 
viduals suffering  from  cancer  of  the  stomach,  whereas  the  stomach  contents  of 
normal  individuals  contains  no  such  enzyme.  The  glycyl-tryptophane  test,  there- 
fore, may  sometimes  furnish  a  means  of  aiding  in  the  diagnosis  of  this  disorder. 
As  applied  to  stomach  contents,  the  test  is  as  follows  :2  Introduce  about  10  c.c.  of 
the  filtrate  from  the  stomach  contents  into  a  test-tube,  add  a  little  glycyl-trypto- 
phane and  a  layer  of  toluene,  and  place  the  tube  hi  an  incubator  at  38°C.  for  24 
hours.  At  the  end  of  this  time  by  means  of  a  pipette  transfer  2-3  c.c.  of  the  fluid 
from  beneath  the  toluene  to  a  test-tube,  add  a  few  drops  of  3  per  cent  acetic  acid 
and  carefully  introduce  bromine  vapors.  Shake  the  tube  and  note  the  production 
of  a  red  color  if  tryptophane  is  present.  The  tryptophane  has,  of  course,  been 
liberated  from  the  peptide  through  the  action  of  the  peptide-splitting  enzyme 
(erepsin)  elaborated  by  the  cancer  tissue. 

If  an  excess  of  bromine  is  added  the  color  will  vanish.  If  no  rose  color  is 
noted,  add  more  bromine  vapors  carefully  with  shaking  until  further  addition  of 
the  vapors  causes  the  production  of  a  yellowish  color.  This  indicates  an  excess 
of  bromine  and  constitutes  a  negative  test.  Occasionally  the  rose  color  indicating 
a  positive  test  is  so  transitory  as  to  escape  detection  unless  the  test  be  very  care- 
fully performed. 

Several  fallacies  have  been  pointed  out  in  connection  with  this  test. 
In  the  first  place  the  regurgitation  of  duodenal  contents  through  the 
pylorus  might  insure  the  presence  in  the  stomach  of  erepsin  and  trypsin 
either  of  which  possesses  peptide-splitting  power.  It  has  also  been 
claimed  that  saliva  contains  an  enzyme  capable  of  splitting  glycyl- 
tryptophane.  Doubt  has,  however,  been  cast  upon  the  dipeptide- 
splitting  agent  of  the  saliva  by  Smithies3 and  by  Jacque  and  Woodyatt,4 
who  point  to  bacteria  as  the  peptolytic  agents.  In  any  event  saliva 
contains  something  which  is  capable  of  splitting  the  glycyltryptophan, 
thus  making  the  entrance  of  saliva  into  the  stomach  an  important 
source  of  error,  so  far  as  the  utility  of  this  test  is  concerned,  as  a  diagnos- 
tic aid.  Bacteria  may,  of  course,  be  removed  from  the  gastric  juice  by 
passing  the  fluid  through  an  effective  filter. 

EXPERIMENTS  ON  INVERTASES5 

i.  Preparation  of  an  Extract  of  Sucrase. — Treat  the  finely  divided  epi- 
thelium of  the  small  intestine  of  a  dog,  pig,  rat,  rabbit,  or  hen  with  about  3 
volumes  of  a  2  per  cent  solution  of  sodium  fluoride  and  permit  the  mixture  to 

xThis  dipeptide  is  sold  commercially  under  the  name  "Ferment  Diagnosticon." 
•Neubauer  and  Fischer:  Deutsches  Archivf.  klinische  Medizin,  97,  499,  1909. 
'Smithies:  Arch.  Int.  Med.,  10,  521,  1912. 

4  Jacque  and  Woodyatt:  Arch.  Int.  Med.,  Dec.,  1912,  p.  560.  v 

6 "The  Inverting  Enzymes  of  the  Alimentary  Tract,"  Mendel  and  Mitchell:  American 
Journal  of  Physiology,  20,  81,  1907-08. 


INTESTINAL  DIGESTION  .  203 

stand  at  room  temperature  for  24  hours.    Strain  the  extract  through  cloth  or 
absorbent  cotton  and  use  the  strained  material  in  the  following  demonstration. 

2.  Demonstration  of  Sucrase.  —  To  about  5  c.c.  of  a  i  per  cent  solution  of 
sucrose,  in  a  test-tube,  add  about  i  c.c.  of  a  2  per  cent  sodium  fluoride  intes- 
tinal extract,  prepared  as  described  above.    Prepare  a  control  tube  in  which  the 
intestinal  extract  is  boiled  before  being  added  to  the  sugar  solution.    Place  the 
two  tubes  at  38°C.  for  two  hours.1    Heat  the  mixture  to  boiling  to  coagulate  the 
protein  material,  filter,  and  test  the  filtrate  by  Fehling's  test  (see  page  25). 
The  tube  containing  the  boiled  extract  should  give  no  response  to  Fehling's  test, 
whereas  the  tube  containing  the  unboiled  extract  should  reduce  the  Fehling's 
solution.    This  reduction  is  due  to  the  formation  of  invert  sugar  (see  page  40) 
from  the  sucrose  through  the  action  of  the  enzyme  sucrase  which  is  present  in 
the  intestinal  epithelium. 

For  preparation  and  demonstration  of  Vegetable  Sucrase  see  Chapter  I. 

3.  Preparation  of  an  Extract  of  Lactase.  —  Treat  the  finely  divided  epithelium 
of  the  small  intestine  of  a  kitten,  puppy,  or  pig  embryo  with  about  3  volumes  of  a 
2  per  cent  solution  of  sodium  fluoride  and  permit  the  mixture  to  stand  at  room 
temperature  for  24  hours.    Strain  the  extract  through  cloth  or  absorbent  cotton 
and  use  the  strained  material  in  the  following  demonstration. 

4.  Demonstration  of  Lactase.2  —  To  about  5  c.c.  of  a  i  per  cent  solution  of 
lactose  in  a  test-tube  add  about  i  c.c.  of  a  toluene-water  or  a  2  per  cent  sodium 
fluoride  extract  of  the  first  part  of  the  small  intestine3  of  a  kitten,  puppy,  or  pig 
embryo  prepared  as  described  above.    Prepare  a  control  tube  in  which  the 
intestinal  extract  is  boiled  before  being  added  to  the  sugar  solution.    Place  the 
two  tubes  at  38°C.  for  24  hours.    At  the  end  of  this  period  add  i  c.c.  of  the  diges- 
tion mixture  to  5  c.c.  of  Barfoed's  reagent4  and  place  the  tubes  in  a  boiling  water- 
bath.6    Examine  the  tubes  at  the  end  of  three  minutes  against  a  black  back- 
ground in  a  good  light.    If  no  cuprous  oxide  is  visible  replace  the  tubes  and 
repeat  the  examination  at  the  end  of  the  fourth  and  fifth  minutes.    If  no  reduc- 
tion is  then  observed  permit  the  tubes  to  stand  at  room  temperature  for  5-10 
minutes  and  examine  again.6 

It  has  been  determined  that  disaccharide  solutions  will  not  reduce  Barfoed's 
reagent  until  after  they  have  been  heated  for  9-10  minutes  on  a  boiling  water- 
bath  in  contact  with  the  reagent.7  Therefore  in  the  above  test,  if  the  tube  con- 
taining the  unboiled  extract  exhibits  any  reduction  after  being  heated  as  indi- 
cated, for  a  period  of  five  minutes  or  less,  and  the  control  tube  containing  boiled 
extract  shows  no  reduction,  it  may  be  concluded  that  lactase  was  present  in  the 
intestinal  extract.8 


1  If  a  positive  result  is  not  obtained  in  this  time  permit  the  digestion  to  proceed  for  a 
longer  period. 

3Roaf:  Bio-Chemical  Journal,  3,  182,  1908. 

3  Duodenum  and  first  part  of  jejunum. 

4  To  4.5  grams  of  neutral  crystallized  copper  acetate  in  900  c.c.  of  water  add  0.6  c.c.  of 
glacial  acetic  acid  and  make  the  total  volume  of  the  solution  i  liter. 

6  Care  should  be  taken  to  see  that  the  water  in  the  bath  reaches  at  least  to  the  upper 
level  of  the  contents  of  the  tubes. 

6  Sometimes  the  drawing  of  conclusions  is  facilitated  by  pouring  the  mixture  from  the 
tube  and  examining  the  bottom  of  the  tube  for  adherent  cuprous  oxide. 

7  The  heating  for  9-10  minutes  is  sufficient  to  transform  the  disaccharide  into  mono- 
saccharide. 

•The  reduction  would,  of  course,  be  due  to  the  action  of  the  glucose  and  galactose 
which  had  been  formed  from  the  lactose  through  the  action  of  the  enzyme  lactase. 


204  PHYSIOLOGICAL  CHEMISTRY 

5.  Preparation  of  an  Extract  of  Maltase. — Treat  the  finely  divided  epithelium 
of  the  small  intestine  of  a  cat,  kitten,  or  pig  (embryo  or  adult)  with  about  3 
volumes  of  a  2  per  cent  solution  of  sodium  fluoride  and  permit  the  mixture  to 
stand  at  room  temperature  for  24  hours.    Strain  the  extract  through  cloth  and 
use  the  strained  material  in  the  f  ollowing  demonstration. 

6.  Demonstration  of  Maltase. — Proceed  exactly  as  indicated  in  the  demon- 
stration of  lactase,  p.  203,  except  that  a  i  per  cent  solution  of  maltose  is  sub- 
stituted for  the  lactose  solution.    The  extract  used  may  be  prepared  from  the 
upper  part  of  the  intestine  of  a  cat,  kitten,  or  pig  (embryo  or  adult).    In  the  case 
of  lactase,  as  indicated,  the  intestine  used  should  be  that  of  a  kitten,  puppy,  or 
pig  (embryo). 


CHAPTER  XII 
BILE 

THE  bile  is  secreted  continuously  by  the  liver  and  passes  into  the 
intestine  through  the  common  bile  duct  which  opens  near  the  pylorus/ 
Bile  is  not  secreted  continuously  into  the  intestine.  In  a  fasting  animal 
no  bile  enters  the  intestine,  but  when  food  is  taken  the  bile  begins  to 
flow;  the  length  of  time  elapsing  between  the  ingestion  of  the  food  and 
the  secretion  of  the  bile  as  well  as  the  qualitative  and  quantitative  char- 
acteristics of  the  secretion  depending  upon  the  nature  of  the  food  ingested. 
Fats,  the  extractives  of  meat  and  the  protein  end-products  of  gas- 
tric digestion  (proteoses  and  peptones) ,  cause  a  copious  secretion  of  bile, 
whereas  such  substances  as  water,  acids  and  boiled  starch  paste  fail ' 
to  do  so.  In  general  a  rich  protein  diet  is  supposed  to  increase  the 
amount  of  bile  secreted,  whereas  a  carbohydrate  diet  would  cause  a 
much  less  decided  increase  and  might  even  tend  to  decrease  the  amount. 
It  has  been  demonstrated  by  Bayliss  and  Starling  that  the  secretion  of 
bile  is  under  the  control  of  the  same  mechanism  that  regulates  the  flow 
of  pancreatic  juice  (see  page  188).  In  other  words,  the  hydrochloric 
acid  of  the  chyme,  as  it  enters  the  duodenum  transforms  prosecretin 
into  secretin  and  this  in  turn  enters  the  circulation,  is  carried  to  the 
liver,  and  stimulates  the  bile-forming  mechanism  to  increased  activity. 

We  may  look  upon  the  bile  as  an  excretion  as  well  as  a  secretion.  In 
the  fulfillment  of  its  excretory  function  it  passes  such  bodies  as  lecithin, 
metallic  substances,  cholesterol,  and  the  decomposition  products  of 
hemoglobin  into  the  intestine  and  in  this  way  aids  in  removing  them 
from  the  organism.  The  bile  assists  materially  in  the  absorption  of 
fats  from  the  intestine  by  its  solvent  action  on  the  fatty  acids  formed 
by  the  action  of  the  pancreatic  juice. 

The  bile  is  a  ropy,  viscid  substance  which  is  usually  alkaline  in  reac- 
tion to  litmus,1  and  ordinarily  possesses  a  decidedly  bitter  taste.  It  varies 
in  color  in  the  different  animals,  the  principal  variations  being  yellow, 
brown  and  green.  Fresh  human  bile  from  the  living  organism  ordi- 
narily has  a  green  or  golden-yellow  color.  Post-mortem  bile  is  variable 
in  color.  It  is  very  difficult  to  determine  accurately  the  amount  of 
normal  bile  secreted  during  any  given  period.  For  an  adult  man  it 

1  It  does  not  contain  more  than  a  slight  excess  of  hydroxylions,  however. 

205 


206 


PHYSIOLOGICAL  CHEMISTRY 


has  been  variously  estimated  at  from  500  c.c.  to  noo  c.c.  for  24  hours. 
The  specific  gravity  of  the  bile  varies  between  i.oio  and  1.040,  and 
the  freezing-point  is  about  —  o.56°C.  As  secreted  by  the  liver,  the 
bile  is  a  clear,  limpid  fluid  which  contains  a  relatively  low  content  of 
solid  matter.  Such  bile  would  have  a  specific  gravity  of  approximately 
i.oio.  After  it  reaches  the  gall-bladder,  however,  it  becomes  mixed 
with  mucous  material  from  the  walls  of  the  gall-bladder,  and  this  proc- 
ess coupled  with  the  continuous  absorption  of  water  from  the  bile  has 
a  tendency  to  concentrate  the  secretion.  Therefore  the  bile  as  we  find  it 
in  the  gall-bladder  ordinarily  possesses  a  higher  specific  gravity  than 
that  of  the  freshly  secreted  fluid.  The  specific  gravity  under  these 
conditions  may  run  as  high  as  1.040. 

The  principal  constituents  of  the  bile  are  the  salts  of  the  bile  acids, 
bile  pigments,  neutral  fats,  lecithin,  phosphatides,  nucleoprotein,  mucin, 
and  cholesterol,  besides  the  salts  of  iron,  copper,  calcium,  and  magnesium. 
Zinc  has  also  frequently  been  found  in  traces.  . 

The  quantitative  composition  of  bile  varies  according  to  the  source 
of  the  bile,  i.e.,  whether  the  bile  for  analysis  is  obtained  from  the  gall- 

QUANTITATIVE  COMPOSITION  OF  BILE1 
(Parts  per  1000) 


Constituent 

Bladder  bile, 
Hammarsten2 

;t 

Biliary  fistula, 
Rosenbloom3 

Water  

829.7 

970.  2 

Solids. 

I7O    3 

7Q     8 

Bile  salts  :  

97.O 

IO.I 

Mucin  and  pigments 

4.1    0 

4  86 

Cholesterol  

9.9 

2.6l6 

Fat  

I    0 

6.85 

Soaps  .... 

II.  24 

2.6 

Lecithin  

2.  2 

6.42 

Inorganic  matter  

C.  I 

9.2 

Fatty  acids 

Included    under    "soaps" 

I  .  2 

*For  other  analyses  see  Czylharz,  Fuchs  and  v.  Fiirth:  Bioch.  Zeit.,  49,  120,  1913. 

2 Hammarsten:  Pincussohn's  Med.-Chem.  Lab.  Hilfsbuch,  Leipzig,  1912,  p.  388. 

'Rosenbloom:  Jour.  Biol.  Chem.,  14,  241,  1913. 

4  Includes  fatty  acids. 

6  Includes  cholesterol  esters. 


BILE  2O7 

bladder  or  by  means  of  a  fistula  before  it  reaches  the  gall-bladder. 
The  variation  in  the  composition  of  these  two  types  of  bile  is  shown  in 
the  preceding  selected  analyses. 

The  bile  acids,  which  are  elaborated  exclusively  by  the  hepatic 
cells,  may  be  divided  into  two  groups,  the  glycocholic  acid  group  and 
the  taurocholic  acid  group.  In  human  bile  glycocholic  acid  predomi- 
nates, while  taurocholic  acid  is  the  more  abundant  in  the  bile  of  car- 
nivora.  The  bile  acids  are  conjugate  amino-acids,  the  glycocholic 
acid  yielding  glycocoll, 

CH2-NH2 

COOH, 

and  cholic  acid  upon  decomposition,  whereas  taurocholic  acid  gives 
rise  to  faurine, 

CH2-NH2 

CH2-S02-OH, 

and  cholic  acid  under  like  conditions.  Glycocholic  acid  contains  some 
nitrogen  but  no  sulphur,  whereas  taurocholic  acid  contains  both  these 
elements.  The  sulphur  of  the  taurocholic  acid  is  present  in  the  taurine 
(amino-ethyl-sulphonic-acid),  of  which  it  is  a  characteristic  constituent. 
There  are  several  varieties  of  cholic  acid  and  therefore  we  have  several 
forms  of  glycocholic  and  taurocholic  acids,  the  variation  in  constitution 
depending  upon  the  nature  of  the  cholic  acid  which  enters  into  the  com- 
bination. The  bile  acids  are  present  in  the  bile  as  salts  of  one  of  the'7 
alkalis,  generally  sodium.  The  sodium  glycocholate  and  sodium  tau- 
rocholate  may  be  isolated  in  crystalline  form,  either  as  balls  or  rosettes 
of  fine  needles  or  in  the  form  of  prisms  having  ordinarily  four  or  six 
sides  (Fig.  61 ,  page  208) .  The  salts  of  the  bile  acids  are  dextro-rotatory. 
Among  other  properties  these  salts  have  the  power  of  holding  the 
cholesterol  and  lecithin  of  the  bile  in  solution. 

It  has  been  shown1  that  a  functionally  defective  liver  (Eck  Fistula) 
produces  less  than  one-half  the  normal  amount  of  bile  acid.  This  is 
direct  evidence  that  the  bile  acids  are  formed  essentially  by  liver 
cell  activity. 

Hammarsten  has  demonstrated  a  third  group  of  bile  acids  in  the 
bile  of  the  shark.  This  same  group  very  probably  occurs  in  certain 
other  animals  also.  These  acids  are  very  rich  in  sulphur  and  resemble 
etheral  sulphuric  acids  inasmuch  as  upon  treatment  with  boiling  hydro- 
chloric acid  they  yield  sulphuric  acid. 

The  bile  pigments  are  important  and  interesting  biliary  constitu- 

^oster,  Hooper,  and  Whipple:  Jour.  Biol.  Chem.,  38,  393,  1920. 


208 


PHYSIOLOGICAL   CHEMISTRY 


ents.  The  following  have  been  isolated:  bilirubin,  biliverdin,  bili- 
fuscin,  biliprasin,  bilihumin,  bilicyanin,  choleprasin,  and  choletelin.  Of 
these,  bilirubin  and  biliverdin  are  the  most  important  and  predominate 
in  normal  bile.  The  colors  possessed  by  the  various  varieties  of  normal 
bile  are  due  almost  entirely  to  these  two  pigments,  the  biliverdin  being 
the  predominant  pigment  in  greenish  bile  and  the  bilirubin  being  the 


FIG.  61. — BILE  SALTS. 

principal  pigment  in  lighter  colored  bile.  The  pigments,  other  than 
the  two  just  mentioned,  have  been  found  almost  exclusively  in  biliary 
calculi  or  in  altered  bile  obtained  at  post-mortem  examinations. 

Bilirubin,  which  is  perhaps  the  most  important  of  the  bile  pigments, 
is  apparently  derived  from  the  blood  pigment,  the  iron  freed  in  the 


t 


FIG.  62. — BILIRUBIN  (HEMATOIDIN).     (Ogden.) 

process  being  held  in  the  liver.  Bilirubin  has  the  same  percentage  com- 
position as  hematoporphyrin,  which  may  be  produced  from  hematin. 
It  is  a  specific  product  of  the  liver  cells,  but  may  also  be  formed  in  other 
parts  of  the  body.  The  pigment  may  be  isolated  in  the  form  of  a 
reddish-yellow  powder  or  may  be  obtained  in  part,  in  the  form  of  reddish- 


BILE  209 

yellow  rhombic  plates  (Fig.  ,62)  upon  the  spontaneous  evaporation 
of  its  chloroform  solution.  The  crystalline  form  of  bilirubin  is 
practically  the  same  as  that  of  hematoidin.  It  is  easily  soluble  in 
chloroform,  somewhat  less  soluble  in  alcohol  and  only  slightly  soluble 
in  ether  and  benzene.  Bilirubin  has  the  power  of  combining  with 
certain  metals,  particularly  calcium,  to  form  combinations  which  are  no 
longer  soluble  in  the  solvents  of  the  unaltered  pigment.  Upon  long 
standing  in  contact  with  the  air,  the  reddish-yellow  bilirubin  is  oxidized 
with  the  formation  of  the  green  biliverdin.  Bilirubin  occurs  in  animal 
fluids  as  soluble  biliru  bin-alkali. 

Solutions  of  bilirubin  exhibit  no  absorption  bands.  If  an  ammonia- 
cal  solution  of  bilirubin-alkali  in  water  is  treated  with  a  solution  of  zinc 
chloride,  however,  it  shows  bands  similar  to  those  of  bilicyanin  (Absorp- 
tion Spectra,  Plate  II),  the  two  bands  between  C  and  D  being  rather 
well  denned. 

Biliverdin  is  particularly  abundant  in  the  bile  of  herbivora.  It  is 
soluble  in  alcohol  and  glacial  acetic  acid  and  insoluble  in  water,  chloro- 
form, and  ether.  Biliverdin  is  formed  from  bilirubin  upon  oxidation. 
It  is  an  amorphous  substance,  and  in  tMs  differs  from  bilirubin  which 
may  be  at  least  partly  crystallized  under  proper  conditions.  Biliverdin 
may  be  obtained  in  the  form  of  a  green  powder.  In  common  with 
bilirubin,  it  may  be  converted  into  hydrobilirubin  by  na'scent  hydrogen. 

The  neutral  solution  of  bilicyanin  or  cholecyanin  is  bluish  green  or 
steel  blue  and  possesses  a  blue  fluorescence,  the  alkaline  solution  is 
green  with  no  appreciable  fluorescence,  and  the  strongly  acid  solution  is 
viole  t  blue.  The  alkaline  solution  exhibits  three  absorption  bands,  the 
first  a  dark,  well-defined  band  between  C  and  D,  somewhat  nearer  C; 
the  second  a  less  sharply  defined  band  extending  across  D  and  the  third 
a  rather  faint  band  between  E  and  F,  near  E  (Absorption  Spectra,  Plate 
II).  The  strongly  acid  solution  exhibits  two  absorption  bands,  both 
lying  between  C  and  E  and  separated  by  a  narrow  space  near  D.  A 
third  band,  exceedingly  faint,  may  ordinarily  be  seen  between  b  and  F. 

Bile  pigments  are  converted  into  urobilinogen  (urobilin)  in  the  intes- 
tine. This  is  absorbed,  carried  to  the  liver  and  reconverted  into  bile 
pigment.  In  diseases  of  the  liver  the  liver  cell  loses  the  capacity  to 
convert  the  urobilinogen  and  this  is  then  excreted  in  the  urine.  The 
presence  of  urobilinogen  in  urine,  therefore,  may  be  considered  as  an 
index  of  functional  liver  incapacity.1  .  ', 

Biliary  calculi,  otherwise  designated  as  biliary  concretions  or  gall 
stones,  are  frequently  formed  in  the  gall-bladder.  These  deposits  may 
be  divided  into  five  classes,  cholesterol  calculi,  cholesterol-calcium 

1Rowntree,  Hurwitz  and  Bloomfield:  Johns  Hopkins  Hospital  Bulletin,  Nov.,  1913. 
14     . 


210  PHYSIOLOGICAL   CHEMISTRY 

calculi,  cholesterol-calcium-pigment  calculi,  calcium- pigment  calculi,  and 
calculi  made  up  almost  entirely  of  inorganic  material.  This  last  class 
of  calculus  is  formed  principally  of  the  carbonate  and  phosphate  of 
calcium  and  is  rarely  found  in  man  although  quite  common  to  cattle. 
The  calcium-pigment  calculus  is  also  found  in  cattle,  but  is  more 
common  to  man  than  the  inorganic  calculus.  This  calcium-pigment 
calculus  ordinarily  consists  principally  of  bilirubin  in  combination  with 
calcium;  biliverdin  is  sometimes  found  in  small  amount.  The  choles- 
terol calculus  is  the  one  found  most  frequently  in  man.  These  may  be 
formed  almost  entirely  of  cholesterol,  in  which  event  the  color  of  the 
calculus  is  very  light,  or  they  may  contain  more  or  less  pigment  and 
inorganic  matter  mixed  with  the  cholesterol,  which  tend  to  give  us 
calculi  of  various  colors. 

For  discussion  of  cholesterol  see  page  3  73 . 

EXPERIMENTS  ON  BILE 

1.  Reaction. — Test  the  reaction  of  fresh  ox  bile  to  litmus,  phenolphthalein  and 
Congo  red. 

2.  Nucleoprotein. — Acidify  a  small  amount  of  bile  with  dilute  acetic  acid.    A 
precipitate  of  nucleoprotein  forms.    Bile  acids  will  also  precipitate  here  under 
proper  conditions  of  acidity. 

3.  Inorganic  Constituents. — Test  for  chlorides,  sulphates,  and  phosphates 
(see  page  58). 

4.  Tests  for  Bile  Pigments. — Practically  all  of  these  tests  for  bile 
pigments  are  based  on  the  oxidation  of  the  pigment,  by  a  variety  of 
reagents,  with  the  formation  of  a  series  of  colored  derivatives,  e.g., 
biliverdin  (green),  bilicyanin  (blue),  choletelin  (yellow). 

(a)  Gmelin's  Test. — To  about  5  c.c.  of  concentrated  nitric  acid  in  a  test-tube 
add  2-3  c.c.  of  diluted  bile  carefully  so  that  the  two  fluids  do  not  mix.    At  the 
point  of  contact  note  the  various  colored  rings,  green,  blue,  violet,  red  and  reddish 
yellow.    Repeat  this  test  with  different  dilutions  of  bile  and  observe  its  delicacy. 

(b)  Rosenbach's  Modification  of  Gmelin's  Test.— Filter  5  c.c.  of  diluted  bile 
through  a  small  filter  paper.    Introduce  a  drop  of  concentrated  nitric  acid  into 
the  cone  of  the  paper  and  note  the  succession  of  colors  as  given  in  Gmelin's  test. 

(c)  Huppert-Cole  Test.1— Boil  about   15   c.c.  of  the  fluid  in  a  test  tube. 
Add  two  drops  of  a  saturated  solution  of  magnesium  sulphate,  then  add  a  10 
per  cent  solution  of  barium  chloride,  drop  by  drop,  boiling  between  each  addi- 
tion.    Continue  to  add  the  barium  chloride  until  no  further  precipitate  is  ob- 
tained.    Allow  the  tube  to  stand  for  a  minute.     Pour  off  the  supernatant  fluid 
as  cleanly  as  possible  or  use  a  centrifuge.    To  the  precipitate  add  3  to  5  c.c. 
of  97  per  cent  alcohol,  two  drops  of  strong  sulphuric  acid,  and  two  drops  of  a 
5  per  cent  aqueous  solution  of  potassium  chlorate.    Boil  for  half  a  minute  and 

dole's  "Practical  Physiological  Chemistry,"  6th  edition,  p.  268,  1920. 


BILE  211 

allow  the  barium  sulphate  to  settle.    The  presence  of  bile  pigments  is  indicated 
by  the  alcoholic  solution  being  colored  a  greenish  blue. 

NOTES. — To  render  the  test  more  delicate,  pour  off  the  alcoholic  solution  from 
the  barium  sulphate  into  a  dry  tube.  Add  about  one-third  its  volume  of  chloro- 
form and  mix.  To  the  solution  add  about  an  equal  volume  of  water,  place  the 
thumb  on  the  tube,  invert  once  or  twice  and  allow  the  chloroform  to  separate. 
It  contains  the  bluish  pigment  in  solution. 

The  bile  pigment  is  adsorbed  on  to  the  barium  sulphate  precipitate,  but  passes 
into  solution  again  in  acid  alcohol.  The  chlorate  acts  as  a  very  weak  oxidizing 
reagent,  converting  bilirubin  and  biliverdin  to  the  characteristic  blue  compound. 

The  author  claims  that  it  is  a  very  much  more  delicate  test  than  Gmelin's 
Test. 

5.  Test  for  Bile  Acids.— (a)  Sucrose-H2SO4  Test  (Pettenkofer).— To  5  c.c. 
of  diluted  bile  in  a  test-tube  add  5  drops  of  a  5  per  cent  solution  of  sucrose.  Now 
run  about  2-3  c.c.  of  concentrated  sulphuric  acid  carefully  down  the  side  of  the 
tube  and  note  the  red  ring  at  the  point  of  contact.  Upon  slightly  agitating  the 
contents  of  the  tube  the  whole  solution  gradually  assumes  a  reddish  color.  As 
the  tube  becomes  warm,  it  should  be  cooled  in  running  water  in  order  that  the 
temperature  of  the  solution  may  not  rise  above  7o°C. 

It  is  claimed  that  this  test  is  not  satisfactory  in  the  presence  of 
protein  and  chromogenic  substances  which  yield  interfering  colors 
with  sulphuric  acid. 

(b)  Furfural-H2SO4  Test— Mylius's  Modification  of  Pettenkofer's  Test— 
To  approximately  5  c.c.  of  diluted  bile  in  a  test-tube  add  3  drops  of  a  very  dilute 
(i  :  1000)  aqueous  solution  of  furfural, 

HC— CH 

II      II 
HC     C-CHO. 


v 


Now  run  about  2-3  c.c.  of  concentrated  sulphuric  acid  carefully  down  the  side  of 
the  tube  and  note  the  red  ring  as  above.  In  this  case,  also,  upon  shaking  the 
tube  the  whole  solution  is  colored  red.  Keep  the  temperature  of  the  solution  be- 
low 7o°C.  as  before. 

(c)  Foam  Test  (v.  Udransky).— To  5  c.c.  of  diluted  bile  in  a  test-tube  add  3-4 
drops  of  a  very  dilute  (i  :  1000)  aqueous  solution  of  furfural.    Place  the  thumb 
over  the  top  of  the  tube  and  shake  the  tube  until  a  thick  foam  is  formed.    By 
means  of  a  small  pipette  add  2-3  drops  of  concentrated  sulphuric  acid  to  the  foam 
and  note  the  dark  pink  coloration  produced. 

(d)  Surface  Tension  Test  (Hay). — This  test  is  based  upon  the  principle  that 
bile  acids  have  the  property  of  reducing  the  surface  tension  of  fluids  in  which  they 
are  contained.    The  test  is  performed  as  follows :  Cool  about  10  c.c.  of  diluted 
bile  hi  a  test-tube  to  i7°C.  or  lower  and  sprinkle  a  little  finely  pulverized  sulphur 
upon  the  surface  of  the  fluid.    The  presence  of  bile  acids  is  indicated  if  the 
sulphur  smks  to  the  bottom  of  the  liquid,  the  rapidity  with  which  the  sulphur  sinks 
depending  upon  the  quantity  of  bile  acids  present  in  the  mixture.    The  test  is  said 
to  react  with  bile  acids  when  they  are  present  in  the  ratio  of  i :  120,000. 


212 


PHYSIOLOGICAL  CHEMISTRY 


(e)  Neukomm's  Modification  of  Pettenkofer's  Test. — To   a  few  drops  of 
diluted  bile  in  an  evaporating  dish  add  a  trace  of  a  dilute  sucrose  solution  and  one 
or  more  drops  of  dilute  sulphuric  acid.     Evaporate  on  a  water-bath  and  note  the 
development  of  a  violet  tolor  at  the  edge  of  the  evaporating  mixture.     Discontinue 
the  evaporation  as  soon  as  the  color  is  observed. 

(f)  Peptone  Test  (Oliver). — To  5  c.c.  of  diluted  bile  add  2-3  drops  of  acetic 
acid,   filtering  if  necessary.      Add  an  equal  volume  of  a  i  per  cent  solution  of 
Witte's  peptone  to  the  acid  solution.    A  precipitate  is  produced  which  is  insoluble 
in  excess  of  acetic  acid.    This  precipitate  is  a  compound  of  protein  and  bile  acids. 

6.  Crystallization  of  Bile  Salts. — To  25  c.c.  of  undiluted  bile  in  an  evaporating 
dish  add  enough  animal  charcoal  to  form  a  paste  and  evaporate  to  dryness  on  a 
water-bath.  Remove  the  residue,  grind  it  in  a  mortar,  and  transfer  it  to  a  small 
flask.  Add  about  50  c.c.  of  95  per  cent  alcohol  and  boil  on  a  water-bath  for  20 
minutes.  Filter,  and  add  ether  to  the  filtrate  until  there  is  a  slight  permanent 
fcloudiness.  Cover  the  vessel  and  stand  it  away  until  crystallization  is  complete. 
Examine  the  crystals  under  the  microscope  and  compare  them  with  those  shown  in 
Fig.  61,  page  208.  Try  one  of  the  tests  for  bile  acids  upon  some  of  the  crystals. 
f-  7.  Analysis  of  Biliary  Calculi. — Grind  the  calculus  in  a  mortar  with  10  c.c. 
of  ether.  Filter. 


Filtrate  I. 


Add  an  equal  volume  of  95  per  cent  alco- 
hol1 to  the  ether  extract,  allow  the  mix- 
ture to  evaporate  and  examine  for  choles- 
terol crystals  (Fig.  63,  page  213).  (For 
further  tests  see  Experiment  8,  below.) 


I 

Residue  1. 

(On  paper  and  in  mortar.) 

Treat  with  dilute  hydrochloric  acid  and 
filter. 


Filtrate  II. 

Test  for  calcium,  phosphates,  and  iron. 
Evaporate  remainder  of  filtrate  to  dry- 
ness  in  porcelain  crucible  and  ignite.  Dis- 
solve residue  hi  dilute  hydrochloric  acid 
and  make  alkaline  with  ammonium  hy- 
droxide. Blue  color  indicates  copper. 


Residue  II. 

(On  paper  and  in  mortar.) 
Wash  with  a  little  water.    Dry  the  filter 
paper. 


Treat  with  5  c.c.  chloroform  and  filter. 


Filtrate  III.  Residue  in. 

Bilirubin.     (On  paper  and  in  mortar.) 
(Apply  test  for 
bile  pigments.) 

Treat  with  5  c.c.  of  hot 
alcohol. 

'  ^  '.  ~ '  . . .    Biliverdin, 

8.  Tests,  for  Cholesterol. 

(a)  Microscopical  Examination. — Examine  the  crystals  under  the  microscope 
and  compare  them  with  those  shown  in  Fig.  63,  below. 

(b)  Sulphuric  Acid  Test  (SalkowsM).— Dissolve  a  few  crystals  of  cholesterol 
in  a  little  chloroform  and  add  an  equal  volume  of  concentrated  sulphuric  acid. 
A  play  of  colors  from  bluish-red  to  cherry-red  and  purple  is  noted  in  the  chloro- 
form while  the  acid  assumes  a  marked  green  fluorescence. 

1  The  alcohol  is  added  because  of  the  fact  that  it  is  often  found  that  crystallization  from 
pure  ether  does  not  yield  typical  cholesterol  crystals. 


BILE  213 

(c)  Acetic    Anhydride-H2SO4    Test    (Liebermann-Burchard).— Dissolve   a 
few  crystals  of  cholesterol  in  2  c.c.  of  chloroform  in  a  dry  test-tube.    Now  add  10 
drops  of  acetic  anhydride  and  1-3  drops  of  concentrated  sulphuric  acid.    The 
solution  becomes  red,  then  blue,  and  finally  bluish-green  in  color.    This  reaction 
is  used  in  the  quantitative  determination  of  cholesterol  (see  Chapter  XVI). 

(d)  Iodine-sulphuric  Acid  Test. — Place  a  few  crystals  of  cholesterol  in  one  of 
the  depressions  of  a  test-tablet  and  treat  with  a  drop  of  concentrated  sulphuric  acid 
and  a  drop  of  a  very  dilute  solution  of  iodine.     A  play  of  colors  consisting  of  violet, 
blue,  green,  and  red  results. 


FIG.  63. — CHOLESTEROL. 

(e)  SchifFs  Reaction. — To  a  little  cholesterol  in  an  evaporating  dish  add  a  few 
drops  of  a  reagent  made  by  adding  i  volume  of  10  per  cent  ferric  chloride  to  3  vol- 
umes of  concentrated  sulphuric  acid.  Evaporate  to  dryness  over  a  low  flame  and 
observe  the  reddish-violet  residue  which  changes  to  a  bluish-violet. 

9.  Preparation  of  Taurine. — To  300  c.c.  of  bile  in  a  casserole  add  100  c.c.  of 
hydrochloric  acid  and  heat  until-  a  sticky  mass  (dyslysin)  is  formed.  This  point 
may  be  determined  by  drawing  out  a  thread-like  portion  of  the  mass  by  means  of  a 
glass  rod,  and  if  it  solidifies  immediately  and  assumes  a  brittle  character  we  may 
conclude  that  all  the  taurocholic  and  glycocholic  acid  has  been  decomposed.  Decant 
the  solution  and  concentrate  it  to  a  small  volume  on  the  water-bath.  Filter  the 
hot  solution  to  remove  sodium  chloride  and  other  substances  which  may  have  sepa- 
rated, and  evaporate  the  filtrate  to  dryness.  Dissolve  the  residue  in  5  per  cent 
hydrochloric  acid  and  precipitate  with  10  volumes  of  95  per  cent  alcohol.  Filter 
off  the  taurine  and  recrystallize  it  from  hot  water.  (Save  the  alcoholic  nitrate  for 
the  preparation  of  glycocoll,  p.  214.)  Make  the  following  tests  upon  the  taurine 
crystals. 

(a)  Examine  them  under  the  microscope  and  compare  with  Fig.  64. 

(6)  Heat  a  crystal  upon  platinum  foil.  The  taurine  at  first  melts,  then  turns 
brown,  and  finally  carbonizes  as  the  temperature  is  raised.  Note  the  suffocating 
odor.  What  is  it? 

(c)  Test  the  solubility  of  the  crystals  in  water  and  in  alcohol. 

(d)  Grind  up  a  crystal  with  four  times  its  volume  of  dry  sodium  carbonate  and 


214 


PHYSIOLOGICAL   CHEMISTRY 


fuse  on  platinum  foil.  Cool  the  residue,  transfer  it  to  a  test-tube,  and  dissolve  it  in 
water.  Add  a  little  dilute  sulphuric  acid  and  note  the  odor  of  hydrogen  sulphide. 
Hold  a  piece  of  filter  paper,  moistened  with  a  small  amount  of  lead  acetate,  over 
the  opening  of  the  test-tube  and  observe  the  formation  of  lead  sulphide. 


FIG.  64. — TAURINE. 

10.  Preparation  of  Glycocoll. — Concentrate  the  alcoholic  nitrate  from  the  last 
experiment  (9)  until  no  more  alcohol  remains.  The  gJycocoll  is  present  here  in  the 
form  of  an  hydrochloride  and  may  be  liberated  from  this  combination  by  the  addi- 


FIG.  65. — GLYCOCOLL. 

tion  of  freshly  precipitated  lead  hydroxide  or  by  lead  hydroxide  solution.  Remove 
the  lead  by  hydrogen  sulphide.  Filter  and  decolorize  the  filtrate  by  animal  char- 
coal. Filter  again,  concentrate  the  filtrate,  and  set  it  aside  for  crystaDization. 
Glycocoll  separates  as  colorless  crystals  (Fig.  65). 


CHAPTER  XIII 
PUTREFACTION  PRODUCTS 

THE  putrefactive  processes  in  the  intestine  are  the  result  of  the 
action  of  bacteria  upon  the  protein  material  present.  This  bacterial 
action  which  is  the  combined  effort  of  many  forms  of  micro-organisms 
is  confined  almost  exclusively  to  the  large  intestine.  Some  of  the  prod- 
ucts of  the  putrefaction  of  proteins  are  identical  with  those  formed 
in  tryptic  digestion,  although  the  decomposition  of  the  protein  material 
is  much  more  extensive  when  subjected  to  putrefaction.  Some  of  the 
more  important  of  the  putrefaction  products  are  the  following:  Indole, 
satole,  paracresol,  phenol,  para-oxyphenylpropionicacid,para-oxyphenyl- 
kacetic  acid,  volatile  fatty  acids,  hydrogen  sulphide,  methane,  methyl 
mercaptan,  hydrogen,  and  carbon  dioxide,  besides  proteases,  peptones, 
peptides,  ammonia,  and  amino-acids.  Basic  substances  such  as  choline, 
neurine,  putrescine  and  cadaverine  are  present  under  certain  conditions. 
Of  the  putrefaction  products  the  indole,  skatole,  phenol,  and  paracresol 
appear  in  part  in  the  urine  as  ethereal  sulphuric  acids,  whereas  the 
oxy  acids  mentioned  pass  unchanged  into  the  urine.  The  potassium 
indoxyl  sulphate  (page  403)  content  of  the  urine  is  a  rough  indicator 
of  the  extent  of  the  putrefaction  within  the  intestine. 

The  portion  of  the  indole  which  is  excreted  in  the  urine  is  first  sub- 
jected to  a  series  of  changes  within  the  organism  and  is  subsequently 
eliminated  as  indican.  These  changes  may  be  represented  thus: 

CH  /\      ^C(OH) 


CH 
NH 

Indoxyl. 

C(0-S03H) 

+H20 
CH 
NH  NH 

Indoxyl.  Indoxyl  sulphuric  acid. 

In  the  presence  of  potassium  salts  the  indoxyl  sulphuric  acid  is  then 
transformed  into  indoxyl  potassium  sulphate  (or  indican), 

C(0-S03K), 


CH 
NH 

and  eliminated  as  such  in  the  urine. 

215 


2l6  PHYSIOLOGICAL   CHEMISTRY 

Indican  may  be  decomposed  by  treatment  with  concentrated  hydro- 
chloric acid  (see  tests  on  page  404)  into  sulphuric  acid  and  indoxyl. 
The  latter  body  may  then  be  oxidized  to  form  indigo-blue  thus: 

CO  OC__      /\ 
!  |  +2H20 

c\A/ 

NH  NH 

Indigo-blue. 

This  same  reaction  may  also  occur  under  pathological  conditions 
within  the  organism,  thus  giving  rise  to  the  appearance  of  crystals  of 
indigo-blue  in  the  urine. 

Skatole  or  methyl  indole  possesses  the  following  structure: 

C(CH3) 


CH 
NH 

In  common  with  indole  it  is  changed  within  the  organism  and  eliminated 
in  the  form  of  a  chromogenic  substance.  Skatole  is,  however,  of  less 
importance  as  a  putrefaction  product  than  indole  and  ordinarily  occurs 
in  much  smaller  amount.  The  tryptophane  group  of  the  protein  mole- 
cule yields  the  indole  and  skatole  formed  in  intestinal  putrefaction,  but 
the  reasons  for  the  transformation  of  the  major  portion  of  this  trypto- 
phane into  indole  and  the  minor  portion  into  skatole  are  not  well  under- 
stood. Indole  is  more  toxic  than  skatole. 

Phenol  occurs  in  fairly  large  amount  in  certain  abnormal  conditions 
of  the  organism,  but  ordinarily  the  amount  is  very  small.  It  is  probably 
derived  from  the  tyrosine  group  of  the  protein  molecule.  Phenol  is 
conjugated  in  the  liver  to  form  phenyl  potassium  sulphate  and  appears 
in  the  urine  in  this  form  (Baumann  and  Herter).  Para-cresol  occurs 
in  the  urine  as  cresyl  potassium  sulphate. 

Regarding  the  claim  of  Nencki  that  methyl  mercaptan  is  formed 
as  a  gas  during  intestinal  putrefaction  it  is  an  important  fact  that 
Herter1  was  unable  to  detect  the  mercaptan  in  fresh  feces.  He  was, 
therefore,  not  inclined  to  accept  the  theory  that  methyl  mercaptan  is 
formed  in  (ordinary  intestinal  putrefaction  but  believed  that  it  may  be 
formed  in  exceptional  cases.  Hydrogen  sulphide  is,  however,  formed  in 
all  cases  of  intestinal  putrefaction. 

It  has  been  demonstrated  that  putrefaction  processes  in  the  human 
intestine  may  be  retarded  by  the  ingestion  of  a  carbohydrate  diet.2  The 
putrefactive  organisms  are  facultative  organisms  and  prefer  a  carbo- 

1  Herter:  "Bacterial  Infections  of  the  Digestive  Tract,  p.  227." 

*  Kendall;  Jour.  Afed.  Res.,  24,  411,  1911;  also  Pediatrics,  23,  No.  9,  1910. 


PUTREFACTION  PRODUCTS  217 

hydrate  medium  if  it  is  available.  These  organisms  are  also  unable  to 
exert  their  maximum  activity  in  an  acid  medium  and  therefore  the 
acids  resulting  from  the  carbohydrate  fermentation  would  tend  to  lessen 
their  activity. 

It  has  been  shown  by  Kutscher  and  his  associates1  that  many  acids 
and  bases  formed  in  putrefaction  and  which  have  been  considered  as 
originating  alone  from  bacterial  action,  may  also  be  formed  in  certain 
phases  of  metabolism  in  both  the  plant  and  animal  kingdoms.  These 
transformation  products  of  amino-acids  have  been  termed  "apor- 
rhegmas."  The  following  aporrhegmas  may  result  from  putrefaction 
processes  : 

Aporrhegma  Ammo-acid  source 

Iminazolethylamine  ........  .  .......................  \  TT-  ,.j. 

Iminazolylpropionic  acid  .....  -.  ...............  .....>/  Hlstldme- 

Orni  thine  .....  ...............  :  ....................  ] 

Tetramethylendiamine  .....  .  .........  ..............  >  Arginine. 

Aminovaleric  acid  .........................  ........  j 

Pentamethylendiamine  ........................  .....     Lysine. 

Amino-butyric  acid  ................................     Glutamic  acid. 


Iso  valeric  acid  ................  ;  .  .  .................     Leucine. 

Phenylethylamirie  ............................. 


Phenylacetic  acid 

Phenylpropionic  acid 

/>-Hydroxyphenylacetic  acid 

/>-Hydroxyphenylpropionic  acid 
Indole... 


Indolylpropionic  acid 


Phenylalanine. 
Tyrosine. 


EXPERIMENTS  ON  PUTREFACTION  PRODUCTS 

In  many  courses  in  physiological  chemistry  the  instructors  are  so 
limited  for  time  that  no  extended  study  of  the  products  of  putrefaction 
can  very  well  be  attempted.  Under  such  conditions  the  scheme  here 
submitted  may  be  used  profitably  in  the  way  of  demonstration.  Where 
the  number  of  students  is  not  too  great,  a  single  large  putrefaction  may 
be  started,  and,  after  the  initial  distillation,  both  the  resulting  distillate 
and  residue  may  be  distributed  to  the  members  of  the  class  for  individual 
manipulation. 

Preparation  of  Putrefaction  Mixture. — Place  a  weighed  mixture  of  coagulated 
egg  albumin  and  ground  lean  meat  in  a  flask  or  bottle  and  add  approximately 
2  liters  of  water  for  every  kilogram  of  protein  used.  Sterilize  the  vessel  and  con- 
tents, inoculate  with  the  colon  bacillus,  and  keep  at  40 °C.  for  two  or  three  weeks. 
If  cultures  of  the  colon  bacillus  are  not  available,  add  60  c.c.  of  a  cold  saturated 

1  Ackermann  and  Kutscher:  Zeit.  physiol.  Chem.,  69,  265,  1910. 
Ackermann:  Ibid.,  273. 
Engeland  and  Kutscher:  Ibid.,  282. 


2l8  PHYSIOLOGICAL  CHEMISTRY 

solution  of  sodium  carbonate  for  every  liter  of  water  previously  added  and 
inoculate  with  some  putrescent  material  (pancreas  or  feces).1  Mix  the  putre- 
faction mixture  very  thoroughly  by  shaking  and  insert  a  cork  furnished  with  a 
glass  tube  to  which  is  attached  a  wash  bottle  containing  a  3  per  cent  solution  of 
mercuric  cyanide.2  This  device  is  for  the  purpose  of  collecting  the  methyl 
mercaptan,  a  gas  formed  during  the  process  of  putrefaction.  It  also  serves  to 
diminish  the  odor  arising  from  the  putrefying  material.  Place  the  putrefaction 
mixture  at  4o°C.  for  two  or  three  weeks  and  at  the  end  of  that  time  make  a  sepa- 
ration of  the  products  of  putrefaction  according  to  the  f ollowing  directions : 

Subject  the  mixture  to  distillation  until  the  distillate  and  residue  are  approxi- 
mately equal  in  volume. 

PART   I 
MANIPULATION  OF  THE  DISTILLATE 

Acidify  with  hydrochloric  acid  and  extract  with  ether. 

I 

I  ~| 

Ether  Extract  No.  i.  Residue  No.  i. 

Add  an  equal  volume  of  water,  make  alka-  Allow  the  ether  to  volatilize.     Evapo- 

line  with  potassium  hydroxide,  and  shake  rate    and    detect    ammonium    chloride 

thoroughly.  crystals  (Fig.  66,  page  219). 

I  I 

Ether  Extract  No.  2.  Alkaline  Solution  No.  i. 

Evaporate    spontaneously.        Indole  and  Acidify  with  hydrochloric  acid,  add 

skatole  remain.  Try  proper  reactions  (see  sodium  carbonate,  and  extract  with 
pages  221  and  222).  ether. 


I  I 

Ether  Extract  No.  3.  Alkaline  Solution  No.  2. 

Evaporate.        Detect    phenol   and  cresott  Acidify  with  hydrochloric  acid,  and 

(paracresole).     See  page  222.  extract  with  ether. 


Ether  Extract  No.  4.  Final  Residue. 

Evaporate.     Volatile  fatty    acids    remain.  (Discard.) 

DETAILED  DIRECTIONS  FOR  MAKING  THE  SEPARATIONS 
INDICATED  IN  THE  SCHEME 

Preliminary  Ether  Extraction.  —  This  extraction  may  be  conveniently  conducted 
in  a  separatory  funnel.  Mix  the  fluids  for  extraction  in  the  ratio  of  two  volumes 
of  ether  to  three  volumes  of  the  distillate.  Shake  very  thoroughly  for  a  few  mo- 
ments, then  jlraw  off  the  extracted  fluid  and  add  a  new  portion  of  the  distillate. 
Repeat  the  process  until  the  entire  distillate  has  been  extracted.  Add  a  small 
amount  of  fresh  ether  at  each  extraction  to  replace  that  dissolved  by  the  water  in 
the  preceding  extraction. 

1  Putrefying  protein  may  be  prepared  by  treating  10  grams  of  finely  ground  lean  meat 
with  roo  c.c.  of  water  and  2  c.c.  of  a  saturated  solution  of  sodium  carbonate  and  keeping 
the  mixture  at  4o°C.  for  24  hours. 

*  Concentrated  sulphuric  acid  containing  a  small  amount  of  isatin  may  be  used  as  a 
substitute  for  mercuric  cyanide.  When  this  modification  is  employed  it  is  necessary  to 
use  calcium  chloride  tubes  to  exclude  moisture  from  the  isatin  solution. 


PUTREFACTION  PRODUCTS 


2I9 


Residue  No.  i. — Unite  the  portions  of  the  distillate  extracted  as  above  and  allow 
the  ether  to  volatilize  spontaneously.  Evaporate  until  crystallization  begins. 
Examine  the  crystals  under  the  microscope.  Ammonium  chloride  predominates. 
Explain  its  presence. 

Ether  Extract  No.  i. — Add  equal  volume  of  water,  render  the  mixture  alkaline 
with  potassium  hydroxide,  and  shake  thoroughly  by  means  of  a  separatory  funnel 
as  before.  The  volatile  Jalty  adds,  contained  among  the  putrefaction  products, 
would  be  dissolved  by  the  alkaline  solution  (No.  i)  whereas  any  indole  or  skatole 
would  remain  in  the  ethereal  solution  (No.  2). 

Alkaline  Solution  No.  i. — Acidify  with  hydrochloric  acid  and  add  sodium 
carbonate  solution  until  the  fluid  is  neutral  or  slightly  acid  from  the  presence  of 
carbonic  acid.  At  this  point  a  portion  of  the  solution,  after  being  heated  for  a  few 
moments,  should  possess  an  alkaline  reaction  on  cooling.  Extract  the  whole  mxi- 
ture  with  ether  in  the  usual  way,  using  care  in  the  manipulation  of  the  stop  cock  to 


FIG.  66. — AMMONIUM  CHLORIDE. 

relieve  the  pressure  due  to  the  evolution  of  carbon  dioxide.  The  ether  (Ether 
Extract  No.  3)  removes  any  phenol  or  cresott  which  may  be  present  while  the 
volatile  fatty  acids  will  remain  in  the  alkaline  solution  (No.  2)  as  alkali  salts. 

Ether  Extract  No.  2. — Drive  off  the  major  portion  of  the  ether  at  a  low  tempera- 
ture on  a  water-bath  and  allow  the  residue  to  evaporate  spontaneously.  Indole 
and  skatole  should  be  present  here.  Prove  the  presence  of  these  bodies.  For 
tests  for  indole  and  skatole  see  pages  221  and  222. 

Alkaline  Solution  No.  2. — Make  strongly  acid  with  hydrochloric  acid  and  ex- 
tract with  a  small  amount  of  ether,  using  a  separatory  funnel.  As  carbon  dioxide  is 
liberated  here,  care  must  be  used  in  the  manipulation  of  the  stop  cock  of  the  funnel 
hi  relieving  the  pressure  within  the  vessel.  The  volatile  fatty  acids  are  dissolved 
by  the  ether  (Ether  Extract  No.  4). 

Ether  Extract  No.  3. — Evaporate  this  ethereal  solution  on  a  water-bath.  The 
oily  residue  contains  phenol  and  cresole.  The  cresole  is  present  for  the  most  part  as 
paracresole".  Add  some  water  to  the  oily  residue  and  heat  it  in  a  flask.  Cool  and 
prove  the  presence  of  phenol  and  cresole.  For  tests  for  these  bodies  see  page  223. 

Ether  Extract  No.  4. — Evaporate  on  a  water-bath.  The  volatile  fatty  acids 
remain  in  the  residue. 


220 


PHYSIOLOGICAL   CHEMISTRY 


PART  II      • 
MANIPULATION  OF  THE  RESIDUE 

Evaporate,  filter,  and  extract  with  ether. 
~~~ I 


Ether  Extract. 

Evaporate,  extract  the  residue  with 
warm  water,  and  filter. 


Filtrate  No.  2. 

Contains  oxyacids  and 
skatole-carbonic  acid. 


Aqueous  Solution. 

Evaporate  until  crystals  begin  to 
form.  Stand  in  a  cold  place  until 
crystallization  is  complete.  Filter. 


• 

Crystalline  Deposit. 
Consists  of  a  mixture  of 
leucine  and  tyro  sine  crystals 
(Figs.  25,  28  and  154,  pages 
75,  79  and  492.) 


I 

Filtrate  No.  i. 

Contains  protease,  peptone, 
aromatic  acids,  and  trypto- 
phane. 


Residue. 

Contains  non-volatile 
fatty  acids. 


DETAILED  DIRECTIONS  FOR  MAKING  THE 

SEPARATIONS   INDICATED    IN 

THE  SCHEME 


Preliminary  Ether  Extraction. — This  extraction  may  be  conducted  in  a  separately 
funnel.  In  order  to  make  a  satisfactory  extraction  the  mixture  should  be  shaken 
thoroughly.  Separate  the  ethereal  solution  from  the  aqueous  portion  and  treat 
them  according  to  the  directions  given  on  page  218. 

Ether  Extract. — Evaporate  this  solution  on  a  safety  water-bath  until  the  ether 
has  been  entirely  removed.  Extract  the  residue  with  warm  water  and  filter. 

Aqueotfs  Solution. — Evaporate  this  solution  until  crystallization  begins.  Stand 
the  solution  in  a  cold  place  until  no  more  crystals  form.  This  crystalline  mass  con- 
sists of  impure  leucine  and  tyrosine.  Filter  off  the  crystals. 

Crystalline  Deposit. — Examine  the  crystals  under  the  microscope  and  compare 
them  with  those  reproduced  in  Figs.  25,  28,  and  145,  pages  75,  79,  and  480.  Do  the 
forms  of  the  crystals  of  leucine  and  tyrosine  resemble  those  previously  examined? 
Make  a  separation  of  the  leucine  and  tyrosine  and  apply  typical  tests  according  to 
directions  given  on  pages  85  and  86. 

Filtrate  No.  i  —Make  a  test  for  tryptophane  with  bromine  water  (see  page  192), 
and  also  with  the  Hopkins-Cole  reagent  (see  page  98).  Use  the  remainder  of  the 
filtrate  for  the  separation  of  proteoses  and  peptones.  Make  the  separation  ac- 
cording to  the  directions  given  on  page  119. 

Filtrate  No.  2.— This  solution  contains  para-oxyphenylacetic  acid,  para-oxy- 
phenylpropionic  acid  and  skatole-carbonic  acid.  Prove  the  presence  of  these 
bodies  by  appropriate  tests.  Tests  for  oxyacids  and  skatole-carbonic  acid  are 
given  on  page  223. 


PUTREFACTION    PRODUCTS  221 

TESTS  FOR  VARIOUS  PUTREFACTION  PRODUCTS 
Tests  for  Indole 

The  various  tests  for  indole  and  skatole  may  be  carried  out  upon  an 
aqueous  solution  of  these  products  or  upon  an  aqueous  solution  j)f 
the  residue  from  Ether  Extract 'No.  2  (see  page  219).  A  distillate 
secured  by  distilling  a  putrefaction  mixture  first  in  alkaline  and  then 
in  acid  reaction  may  also  be  employed. 

1.  Herter's  /3-Naphthaquinone  Reaction. — (a)  To  a  dilute  aqueous  solution 
of  indole  (i :  500,000)  add  i  drop  of  a  2  per  cent  solution  of  j3-naphthaquinone- 
sodium-monosulphonate.    No  reaction  occurs.    Add  a  drop  of  a  10  per  cent 
solution  of  potassium  hydroxide  and  note  the  gradual  development  of  a  blue 
or  blue-green  color  which  fades  to  green  if  an  excess  of  the  alkali  is  added. 
Render  the  green  or  blue-green  solution  acid  and  note  the  appearance  of  a 
pink  color.    Heat  facilitates  the  development  of  the  color  reaction. 

One  part  of  indole  hi  one  million  parts  of  water  may  be  detected  by  means  of 
this  test  if  carefully  performed. 

(b)  If  the  alkali  be  added  to  a  more  concentrated  indole  solution  before  the 
introduction  of  the  naphthaquinone,  the  course  of  the  reaction  is  different, 
particularly  if  the  indole  solution  is  somewhat  more  concentrated  than  that  men- 
tioned above  and  if  heat  is  used.  Under  these  conditions  the  blue  indole  com- 
pound ultimately  forms  as  fine  acicular  crystals  which  rise  to  the  surface. 

If  we  do  not  wait  for  the  production  of  the  crystalline  body  but  as  soon  as  the 
blue  color  forms,  shake  the  aqueous  solution  with  chloroform,  the  blue  color  dis- 
appears from  the  solution  and  the  chloroform  assumes  a  pinkish-red  hue. 
This  is  a  distinguishing  feature  of  the  indole  reaction  and  facilitates  the  differen- 
tiation of  indole  from  other  bodies  which  yield  a  similar  blue  color.  A  very  sat- 
isfactory method  for  the  quantitative  determination  of  indole  is  based  upon  the 
principle  underlying  this  test  (see  chapter  on  Feces). 

2.  Formaldehyde  Reaction  (Konto). — To  i  c.c,  of  the  material  under  exami- 
nation hi  a  test-tube  add  3  drops  of  a  40  per  cent  solution  of  formaldehyde  and  i 
c.c.  of  concentrated  sulphuric  acid.    Now  agitate  the  mixture  and  note  the  appear- 
ance of  a  violet-red  color  if  a  trace  of  indole  is  present.    The  test  is  said  to  serve 
for  the  detection  of  indole  when  present  hi  a  dilution  of  i :  700,000. 

Skatole  gives  a  yellow  or  brown  color  under  the  above  conditions. 
:  3.  Cholera-red  Reaction.— To  a  little  of  the  material  under  examination  in  a 
test-tube  add  one-tenth  its  volume  of  a  0.02  per  cent  solution  of  potassium  nitrite 
and  mix  thoroughly.  Carefully  run  concentrated  sulphuric  acid  down  the  side 
of  the  tube  so  that  it  forms  a  layer  at  the  bottom.  Note  the  purple  color.  Neu- 
tralize with  potassium  hydroxide  and  observe  the  production  of  a  bluish-green 
color. 

4.  Nitroprusside  Reaction  (Legal). — To 'a  small  amount  of  the  material  under 
examination  in  a  test-tube  add  a  few  drops  of  a  freshly  prepared  solution  of  sodium 
nitroprusside,  Na2Fe(CN)sNO  +  2H2O.  Render  alkaline  with  potassium  hydroxide 
and  note  the  production  of  a  violet  color.  If  the  solution  is  now  acidified  with 
glacial  acetic  acid  the  violet  is  transformed  into  a  blue. 


222  PHYSIOLOGICAL  CHEMISTRY 

5.  Pine  Wood  Test. — Moisten  a  pine  splinter  with  concentrated  hydrochloric 
acid  and  insert  it  into  the  material  under  examination.    The  wood  assumes  a 
cherry-red  color. 

6.  Nitroso-indole  Nitrate  Test. — Acidify  some  of  the  material  under  examina- 
tion with  nitric  acid,  add  a  few  drops  of  a  potassium  nitrite  solution  and  note  the 
production  of  a  red  precipitate  of  nitroso-indole  nitrate.    If  the  residue  contains 
but  little  indole  simply  a  red  coloration  will  result.     Compare  this  result  with  the 
result  of  the  similar  test  on  skatole. 


Tests  for  Skatole 

1.  Better's  Para-dimethylaminobenzaldehyde  Reaction.1— To  5  c.c.  of  the 
distillate  or  aqueous  solution  under  examination  add  i  c.c.  of  an  acid  solution  of 
para-dimethylaminobenzaldehyde2  and  heat  the  mixture  to  boiling.    A  purplish- 
blue  coloration  is  produced3  which  may  be  intensified  through  the  addition  of  a 
few  drops  of  concentrated  hydrochloric  acid.    If  the  solution  be  cooled  under 
running  water  it  loses  its  purplish  tinge  of  color  and  becomes  a  definite  blue. 
The  solution  at  this  point  may  be  somewhat  opalescent  through  the  separation  of 
uncombined  para-dimethylaminobenzaldehyde.    Care  should  be  taken  not  to 
add  an  excess  of  hydrochloric  acid  inasmuch  as  the  end-reaction  has  a  tendency 
to  fade  under  the  influence  of  a  high  acidity. 

A  rough  idea  regarding  the  actual  quantity  of  skatole  in  a  mixture  may  be 
obtained  by  extracting  this  blue  solution  with  chloroform  and  subsequently 
comparing  this  chloroform  solution,  by  means  of  a  colorimeter  (Duboscq),  with 
the  maximal  reaction,  obtained  with  a  skatole  solution  of  known  strength. 

2.  Color  Reaction  with  Hydrochloric  Acid. — Acidify  some  of  the  residue  with 
concentrated  hydrochloric  acid.     Note  the  production  of  a  violet  color. 

3.  Acidify  some  of  the  residue  with  nitric  acid  and  add  a  few  drops  of  a  potas- 
sium nitrite  solution.     Note  the  white  turbidity.     Compare  this  result  with  the 
result  of  the  similar  test  on  indole. 


Tests  for  Phenol  and  Cresole 

1.  Color  Test.—  Test  a  little  of  the  solution  with  Millon's  reagent.    A  red 
color  results.    Compare  this  test  with  the  similar  one  under  Tyrosine  (see  page 
85). 

2.  Ferric  Chloride  Test.  —  Add  a  few  drops  of  neutral  ferric  chloride  solution 
to  a  little  of  the  material  under  examination.    A  dirty  Wuish-gray  color  is  formed. 

3.  Formation  of  Bromine  Compounds.  —  Add  some  bromine  water  to  a  little 
of  the  fluid  under  examination.    Note  the  crystalline  precipitate  of  tribrom- 
phenol  and  tribromcresol.    The  reaction  for  phenol  is  as  follows  : 


Phenol.  Tribromphenol. 

1  Herter:  Bacterial  Infections  of  the  Digestive  Tract,  1907,  p.  141. 
*  Made  by  dissolving  5  grams  of  para-dimethylaminobenzaldehyde  in  100  c.c.  of  10 
per  cent  sulphuric  acid. 

•If  the  color  does  not  appear  add  more  of  the  aldehyde  solution! 


PUTREFACTION  PRODUCTS  223 

4.  Nitric  Acid  Test. — Add  some  nitric  acid  to  some  of  the  material  under 
examination.  Heat  and  note  a  yellow  color  due  to  the  production  of  picric  acid 
( trinitrophenol)  from  phenol.  This  is  the  reaction : 


Phenol.  Picric  acid. 

Tests  for  Oxyacids 

1.  Color  Test. — Test  a  little  of  the  solution  with  Millon's  reagent.    A  red  color 
results. 

2.  Bromine  Water  Test. — Add  a  few  drops  of  bromine  water  to  some  of  the 
filtrate.    A  turbidity  or  precipitate  is  observed. 

Test  for  Skatole -carbonic  Acid 

Ferric  Chloride  Test. — Acidify  some  of  the  filtrate  with  hydrochloric  acid,  add 
a  few  drops  of  ferric  chloride  solution,  and  heat.  Compare  the  end-reaction  with 
that  given  by  phenol. 


CHAPTER  XIV 
FECES 

THE  feces  are  the  residual  mass  of  material  remaining  in  the  intes- 
tine after  the  full  and  complete  exercise  of  the  digestive  and  absorptive 
functions  and  are  ultimately  expelled  from  the  body  through  the  rectum. 

They  may  be  said  to  be  composed  of  the  following  substances: 

1.  Food  residues:  (a)  those  portions  of  the  food  which  have  escaped 
absorption,  and  (b)  that  part  of  the  diet  either  not  digested  or  incapable 
of  absorption. 

2.  The   remains   of   the   intestinal   and   digestive   secretions   not 
destroyed  or  reabsorbed. 

3.  Substances  excreted  into  the  intestinal  tract,  notably  salts  of 
calcium,  iron,  and  other  metals. 

4.  The  bacterial  flora  of  the  intestinal  tract. 

5.  Cellular  elements  to  which  may  be  added,  under  pathological 
conditions,  blood,  pus,  mucus,  serum,  and  parasites. 

6.  Abnormally:  enteroliths,  gall  stones,  and  pancreatic  calculi. 
The  amount  of  the  fecal  discharge  varies  with  the  individual  and  the 

diet.  Upon  an  ordinary  mixed  diet  various  authorities  claim  that  the 
daily  excretion  by  an  adult  male  will  aggregate  110-170  grams  with  a 
solid  content  ranging  between  25  and  45  grams;  the  fecal  discharge  of 
such  an  individual  upon  a  vegetable  diet  will  be  much  greater  and  may 
even  be  as  great  as  350  grams  and  possess  a  solid  content  of  75  grams. 
In  the  author's  own  experience  the  average  daily  output  of  moist  feces, 
calculated  on  the  basis  of  data  secured  from  the  examination  of  over 
1000  stools,  was  about  100  grams.  The  variation  in  the  normal  daily 
output  being  so  great  renders  this  factor  of  very  little  value  for  diag- 
nostic purposes,  except  where  the  composition  of  the  diet  is  accurately 
known.  Lesions  of  the  digestive  tract,  a  defective  absorptive  function, 
or  increased  peristalsis  as  well  as  an  admixture  of  mucus,  pus,  blood, 
and  pathological  products  of  the  intestinal  wall,  may  cause  the  total 
amount  of  excrement  to  be  markedly  increased.  An  idea  of  the  varia- 
tion of  the  percentage  of  dry  matter  in  the  feces,  evacuated  after  the 
ingestion  of  different  diets,  may  be  gathered  from  a  consideration  of  the 
following  table.1 

Schmidt  &  Strasburger:  "Die  Fazes  des  Menschen,"  Berlin,  1915.  :' 

224 


FECES  225 

INFLUENCE  OF  DIET  ON  FECAL  DRY  MATTER 


Diet 


Dry  Matter  Percent. 


f  Nursing  infant. 
Milk 

(  Adult 

Meat 

Bread 

Potatoes 

Cabbage. 

Mixed  Diet . . 


28.0 
29.0 
25.0 

i5-o 

4.4 

26.0 


Color  of  crystals  same  as  the  color 
Of  those  in  Fig.  62,  page  208, 


The  fecal  pigment  of  the  normal  adult  is  hydrobilirubin.  This 
pigment  originates  from  the  bilirubin  which  is  secreted  into  the  intes- 
tine in  the  bile,  the  transformation  from  bilkubin  to  hydrobilirubin 
being  brought  about  through  the  activity  of  certain  bacteria.  Hydro- 
bilirubin  is  sometimes  called  stercobilin 
and  bears  a  close  resemblance  to  urobilin 
or  may  even  be  identical  with  that  pig- 
ment. Neither  bilirubin  nor  biliverdin 
occurs  normally  in  the  fecal  discharge  of 
adults,  although  the  former  may  be  de- 
tected in  the  excrement  of  nursing  in-. 
fants.  If  these  pigments  are  found  in 
the  feces  of  adults,  they  indicate  an 
abnormally  rapid  transit  through  the 

large  bowel  thus  preventing  their  trans- 
.  .  .  ,      .     .  ...      .  .          _ 

formation     into     hydrobilirubin.     Fre- 

quently,  in  some  way  as  yet  unknown, 

probably  through  the  agency  of  certain  bacterial  processes,  color- 
less hydrobilirubinogen  (leucohydrobilirubin)  is  formed  which  after 
the  passage  of  the  movement  and  exposure  to  air  is  reconverted 
into  hydrobilirubin.  This  may  explain  in  some  cases  the  darken- 
ing of  the  stool  when  exposed  to  the  air.  The  most  important 
factor  in  determining  the  color  of  the  fecal  discharge  is  the  diet.  A 
mixed  diet,  for  instance,  produces  stools  which  vary  in  color  from  light 
to  dark  brown,  an  exclusive  meat  diet  gives  rise  to  a  brownish-black 
stool,  whereas  the  stool  resulting  from  a  milk  diet  is  invariably  light 
colored.  Certain  pigmented  foods,  such  as  the  chlorophyllic  vegetables 
and  various  varieties  of  berries,  each  afford  stools  having  a  characteristic 
color.  Certain  drugs  act  in  a  similar  way  to  color  the  fecal  discharge. 
This  is  well  illustrated  by  the  occurrence  of  green  stools  following  the  use 
of  calomel,  of  black  stools  after  bismuth  ingestion,  and  of  yellow  stools 
following  the  administration  of  rhubarb,  senna  or  santonin.  The  green 
15 


226  PHYSIOLOGICAL   CHEMISTRY 

color  of  the  calomel  stool  is  generally  believed  to  be  due  to  biliverdin. 
v.  Jaksch,  however,  claims  to  have  proven  this  view  to  be  incorrect 
since  he  was  able  to  detect  hydrobilirubin  (or  urobilin)  but  no  biliverdin 
in  stools  after  the  administration  of  calomel.  The  bismuth  stool  was  at 
one  time  thought  to  derive  its  color  from  the  black  sulphide  which  is 
formed  from  the  subnitrate  of  bismuth.  We  now  know1  that  the  color 
is  due  to  the  reduction  of  the  bismuth  compound  (subnitrate)  to  bismuth 
suboxide.  In  cases  of  biliary  obstruction  the  grayish-white  acholic 
stool  is  formed. 

Under  normal  conditions  the  odor  of  feces  is  due  to  skatole  and 
indole,  two  bodies  formed  in  the  course  of  putrefactive  processes  occur- 
ring within  the  intestine  (see  page  215).  Such  bodies  as  methane, 
methyl  mercaptan,  and  hydrogen  sulphide  may  also  add  to  the  disagree- 
able character  of  the  odor.  The  intensity  of  the  odor  depends  to  a 
large  degree  upon  the  character  of  the  diet,  being  very  marked  in  stools 
from  a  meat  diet,  much  less  marked  in  stools  from  a  vegetable  diet,  and 
frequently  hardly  detectable  in  stools  from  a  milk  diet.  Thus  the  stool 
of  the  infant  is  ordinarily  nearly  odorless  and  any  decided  odor  may 
generally  be  readily  traced  to  some  pathological  source. 

A  neutral  reaction  ordinarily  predominates  in  normal  stools,  although 
slightly  alkaline  or  even  acid  stools  are  met  with.  The  acid  reaction  is 
encountered  much  less  frequently  than  the  alkaline,  and  then  commonly 
only  following  a  vegetable  diet. 

Experiments  in  which  the  actual  hydrogen  ion  concentration  of  the 
feces  was  determined  indicate  that  the  reaction  of  the  excreta  is  uni- 
formly slightly  alkaline.'2'  Pronounced  dietary  changes,  e.g.,  low  protein 
diet,  high  protein  diet,  fasting,  water  drinking  with  meals,  produce  at 
most  only  minor  changes  in  the  reaction  of  the  feces. 

The  form  and  consistency  of  the  stool  is  dependent,  in  large  measure, 
upon  the  nature  of  the  diet.  Under  normal  conditions  the  consistency 
may  vary  from  a  thin,  pasty  discharge  to  a  firmly  formed  stool.  Stools 
which  are  exceedingly  thin  and  watery  ordinarily  have  a  pathological 
significance.  In  general  the  feces  of  the  carnivorous  animals  are  of  a 
firmer  consistency  than  those  of  the  herbivora. 

The  continued  ingestion  of  a  diet  which  is  very  thoroughly  digested 
and  absorbed  is  frequently  accompanied  by  the  formation  of  dry,  hard 
fecal  masses  (scybala) .  Constipation  generally  results,  due  to  the  small 
bulk  of  the  feces  and  its  lack  of  moisture.  At  present  the  formation  of 
scybala  is  considered  pathological,  as  an  expression  of  spastic  constipa- 
tion. To  counteract  this  tendency  toward  constipation  the  ingestion 

1Quincke:  Miinch.  med.  Woch.,  p.  854,  1896. 

2 Howe  and  Hawk:  Jour.  Biol.  Chem.,  u,  129,  1912. 


FECES  227 

of  agar-agar1  has  been  suggested.2  This  agar  is  relatively  indigestible 
and  readily  absorbs  water  (about  16  times  its  weight),  thus  forming  a 
bulky  fecal  mass  which  is  sufficiently  soft  to  permit  of  easy  evacuation. 
Agar  is  not  limited  to  its  use  in  connection  with  constipation;  it  may 
serve  in  other  capacities  as  an  aid  to  intestinal  therapeutics  by  serving 
as  a  vehicle  for  certain  drugs.3 

It  is  frequently  desirable  for  clinical  or  experimental  purposes  to 
make  an  examination  of  the  fecal  output  which  constitutes  the  residual 
mass  from  a  certain  definite  diet.  Under  such  conditions,  it  is  custom- 
ary to  cause  the  person  under  observation  to  ingest  some  substance,  at 
the  beginning  and  end  of  the  period  in  question,  which  shall  sufficiently 
differ  in  color  and  consistency  from  the  surrounding  f eces  as  to  render 
comparatively  easy  the  differentiation  of  the Jeces  of  that  period  from 
the  feces  of  the  immediately  preceding  and  succeeding  periods.  One 
of  the  most  satisfactory  methods  of  making  this  "separation"  is  by 
means  of  the  ingestion  of  a  gelatin  capsule  containing  about  0.2  gram  of 
powdered  charcoal  at  the  beginning  and  end  of  the  period  under  observa- 
tion. This  procedure  causes  the  appearance  of  two  Hack  zones  of  char- 
coal in  the  fecal  mass  and  thus  renders  comparatively  simple  the 
differentiation  of  the  feces  of  the  intermediate  period.  Carmine  (0.3 
gram)  may  be  used  in  a  similar  manner  and  forms  two  dark  red  zones. 
Some  similar  method  for  the  "separation  of  feces"  is  universally 
practised  in  connection  with  the  scientifically  accurate  type  of  nutrition 
or  metabolism  experiment  which  embraces  the  collection  of  useful  data 
regarding  the  income  and  outgo  of  nitrogen  and  other  elements. 

Among  the  macroscopical  constituents  of  the  feces  may  be  men- 
tioned the  following:  Intestinal  parasites  and  their  ova,  undigested 
food  particles,  gall  stones,  pathological  products  of  the  intestinal  wall, 
enteroliths,  intestinal  sand,  and  objects  which  have  been  accidentally 
swallowed. 

The  fecal  constituents  which  at  various  times  and  under  different 
conditions  may  be  detected  by  the  use  of  the  microscope  are  as  follows: 
Constituents  derived  from  the  food,  such  as  muscle  fibers,  connective- 
tissue  shreds,  starch  granules,  and  fat;  form  elements  derived  from 
the  intestinal  tract,  such  as  epithelium,  erythrocyies,  and  leucocytes; 
mucus;  pus  corpuscles;  parasites  and  bacteria.  In  addition  to  the  con- 
stituents named  the  following  crystalline  deposits  may  be  detected: 
cholesterol,  koprosterol,  soaps,  fatty  acid,  fat,  hematoidin,  "triple  phos- 

1  Agar-agar  is  a  product  prepared  from  certain  types  of  Asiatic  sea- weed.    It  is  a  carbo* 
hydrate  and  is  classified  as  a  galactan  in  the  polysaccharide  group. 

2  Mendel:  Zent.f.  ges.  PhysioL  u.  Path,  des  Stoffw.,  No.  17,  p.  i,  1908;  Schmidt:  Miinch* 
med.  Woch.,  52,  1970,  1905. 

3Einhorn:  Berl.  klin.  Woch.,  49,  113,  1912. 


228  PHYSIOLOGICAL   CHEMISTRY 

phate,"  Char  cot-Ley  den  crystals,  and  the  oxalate,  carbonate,  phosphate, 
sulphate,  and  lactate  of  calcium.  (See  Figs.  70  to  75,  pp.  233  and  234.) 
The  koprosterol  of  the  feces  is  similar  to  cholesterol,  and  may  be 
formed  by  the  reduction  of  the  latter.  It  responds  to  cholesterol  color 
tests  and  has  the  same  solubility,  but  possesses  a  lower  melting-point  and 
crystallizes  in  fine  needles  instead  of  plates  such  as  cholesterol  forms. 

The  detection  of  minute  quantities  of  blood  in  the  feces  ("occult 
blood")  has  recently  become  a  recognized  aid  to  a  correct  diagnosis  of 
certain  disorders.  In  these  instances  the  hemorrhage  is  ordinarily  so 
slight  that  the  identification  by  means  of  macroscopical  characteristics 
as  well  as  the  microscopical  identification  through  the  detection  of  ery- 
throcytes  are  both  unsatisfactory  in  their  results.  Of  the  tests  given 
for  the  detection  of  " occult  blood"  the  benzidine  reaction,  Lyle-Cuft- 
man  guaiac  procedure  and  the  hematein  tests  (page 
238)  are  probably  the  most  satisfactory.  Since 
" occult  blood"  occurs  with  considerable  regularity 
and  frequency  in  gastrointestinal  cancer  and  in 
gastric  and  duodenal  ulcer,  its  detection  in  the  feces 
is  of  especial  value  as  an  aid  to  a  correct  diagnosis  of 

FIG.  68.— CHARCOT-  these  disorders.  Certain  precautions  are  essential. 
LEYDF.N  CRYSTALS.  ,  .,  A  ,  ,.  ,  P  .  .. 

such  as  the  establishment  of  a  meat-free  diet  over  a 

period  of  time  before  the  specimen  is  collected.  (Feces  from  a  meat 
diet  will  give  an  occult  blood  reaction  with  some  of  the  most  delicate 
tests.)  Bleeding  from  the  bowel  such  as  is  seen  in  hemorrhoids,  as 
well  as  the  admixture  of  menstrual  blood,  is  to  be  considered  in  the 
interpretation  of  the  result. 

It  has  been,  quite  clearly  shown  that  the  intestine  of  the  newly  born 
is  sterile.  However,  this  condition  is  quickly  altered  and  bacteria  may 
be  present  in  the  feces  before  or  after  the  first  ingestion  of  food.  There 
are  three  possible  means  of  infecting  the  intestine,  i.e.,  by  way  of  the 
mouth  or  anus  or  through  the  blood.  The  infection  by  means  of  the 
blood  seldom  occurs  except  under  pathological  conditions,  thus  limit- 
ing the  general  infection  to  the  mouth  and  anus. 

In  infants  with  pronounced  constipation  two-thirds  of  the  dry  sub- 
stance of  the  stools  has  been  found  to  consist  of  bacteria.  In  the  stools 
of  normal  adults  probably  about  one-third  of  the  dry  substance  is 
bacteria.1  The  average  excretion  of  dry  bacteria  in  24  hours  for  an 
adult  is  about  8  grams.  The  output  of  fecal  bacteria  has  been  found 
to  undergo  a  decrease  under  the  influence  of  water  drinking  with  meals.2 

1  Schittenhelm  and  Tollens  found  bacteria  to  comprise  42  per  cent  of  the  dry  matter. 
This  value  is,  however,  undoubtedly  too  high. 

2Mattill  and  Hawk:  Jour.  Am.  Chem.  Soc.,  33,  1999,  1911;  Blatherwick  and  Hawk: 
Bioch.  Bull.;  3,  28,  1913. 


FECES  229 

There  was  also  a  decrease  in  intestinal  putrefaction,1  a  fact  which 
indicates  that  at  least  a  part  of  the  bacterial  deficit  was  made  up  of 
putrefactive  organisms.  In  some  cases  over  50  per  cent  of  the  total 
nitrogen  of  feces  has  been  shown  to  be  bacterial  nitrogen* 

Various  enzymes  have  been  detected  in  the  feces.  The  first  one  so 
demonstrated  was  pancreatic  amylase.3  The  amylase  content  of  the 
feces  is  believed  to  be  an  index  of  the  activity  of  the  pancreatic  function.4 
The  excretion  of  this  enzyme  has  been  found  to  increase  under  the 
influence  of  water  drinking  with  meals.5  Other  enzymes  which  have 
been  found  in  the  fec_es  under  various  conditions  are  trypsin,  rennin, 
maltase,  sucrase,  lactase,  nuclease  and  lipase.6  In  an  abnormally  rapid 
transit  of  food  through  the  intestinal  tract,  such  as  is  seen  in  certain 
diarrheas,  nearly  all  of  these  enzymes  may  be  detected. 

Some  of  the  more  important  organisms  met  with  in  the  feces  are  the 
following:7  B.  coli,  B.  lactis  aerogenes,  Bact.  Welchii,  B.  bifidus,  and 
coccal  forms.  Of  these  the  first  three  types  mentioned  are  gas-forming 
organisms.  The  production  of  gas  by  the  fecal  flora  in  dextrose- 
bouillon  is  subject  to  great  variations  under  pathological  conditions; 
alterations  in  the  diet  of  normal  persons  will  also  cause  wide  fluctuations. 
Data  as  to  the  production  of  gas  are  of  considerable  importance  in  a 
diagnostic  way,  although  the  exact  cause  of  the  variation  is  not  yet 
established.  It  should  be  borne  in  mind  in  this  connection  that  gas 
volumes  are  frequently  variable  with  the  same  individual.  For  this 
reason  it  is  necessary  in  every  instance  to  follow  the  gas  production  for 
a  considerable  period  of  time  before  drawing  conclusions.8  While  the 
question  of  the  study  of  bacterial  flora  of  the  feces  is  a  question  beyond 
the  range  of  this  work,  mention  may  be  made  here  of  the  character  of 
the  organisms  observed  by  Gram  staining  of  the  stool  after  administra- 
tion of  different  types  of  diet.  It  has  been  shown  that  when  the  diet 
is  markedly  protein,  the  protein  type  of  flora  becomes  predominant  in 
the  stools.  Gram-stained  smears  show  a  fairly  equal  distribution  of 
Gram-negative  and  Gram-positive  organisms.  Among  the  latter  are 
largely  the  subtiloid  organisms  with  some  of  the  Bact.  Welchii,  together 
with  a  moderate  number  of  diplococci  and  coccoid  forms.  Most  of  the 
Gram-negative  organisms  resemble  the  B.  coli.  When  the  diet  is 

1Hattrem  and  Hawk:  Arch.  Int.  Med.,  7,  610,  1911;  Blatherwick,  Sherwin  and  Hawk: 
loc.  cit. 

2MacNeal,  Latzer  and  Kerr:  Jour.  Inf.  Dis.,  6,  123,  1909;  Mattill  and  Hawk:  Jour. 
Exp.  Med.,  14,  433,  1911;  Blatherwick  and  Hawk:  Biochem.  Bull.,  3,  28,  1913. 

3Wegscheider:  Inaug.  Diss.,  Strassburg,  1875. 

4  Wohlgemuth :  Berl.  klin.  Woch.,  47,  3,  92,  1910. 

'Hawk:  Arch.  Int.  Med.,  8,  382,  1911. 

•Ury:  Biochem.  Zeit.,  23,  152,  1909. 

7Herter  and  Kendall:  Journal  of  Biological  Chemistry,  5,  283,  1908 

8Herter  and  Kendall:  loc.  cit. 


230  PHYSIOLOGICAL   CHEMISTRY 

carbohydrate  the  field  is  strongly  Gram  positive  and  has  a  more  homo- 
geneous appearance.  The  bacteria  seen  consist  chiefly  of  long  slender 
Gram-positive  rods  belonging  to  the  B.  acidophilus  and  B.  bifidus 
groups.1 

The  nitrogen  present  in  the  feces  exists  principally  in  the  form  of 
bacteria ,  unabsorbed  intestinal  secretions  and  digestive  juices,  epithelial 
cells,  mucus  material  and  food  residues.  In  the  early  days  of  nutrition 
study  the  fecal  nitrogen  was  believed  to  consist  principally  of  food 
residues.  We  now  know  that  such  residues  ordinarily  make  up  but 
a  small  part  of  the  nitrogen  quota  of  the  stools  of  normal  individuals 
who  exercise  normal  mastication.2  When  meat  has  been  "bolted," 
however,  from  0.5  gram  to  16  grams  of  macroscopical  meat  residues 
have  been  found  in  a  single  stool.3  The  phrase  " metabolic  product 
nitrogen"  is  frequently  used  as  a  designation  for  all  fecal  nitrogen 
except  that  present  as  food  residues  and  bacteria.  Bacteria  cannot 
logically  be  classed  under  "metabolic"  nitrogen  since  they  doubtless 
develop  at  the  expense  of  food  nitrogen  as  well  as  at  the  expense  of 
that  in  the  form  of  intestinal  secretions.  In  the  accurate  study  of 
"protein  utilization"4  a  correction  should  be  made  for  "metabolic 
nitrogen."  Data  regarding  the  output  of  metabolic  nitrogen  may  be 
secured  by  determining  the  fecal  nitrogen  excretion  on  a  diet  of  proper 
energy  value  but  containing  no  nitrogen.5  Agar-agar  may  be  utilized 
advantageously  in  connection  with  such  a  nitrogen-free  diet. 

The  importance  of  the  intestine  as  an  excretory  organ  has  been 
emphasized  particularly  by  Myers  and  Fine6  who  have  reported  quite 
an  extended  study  of  the  inorganic  constituents  of  feces. 

Feces  are  still  excreted  from  the  intestine  even  when  no  food  is 
ingested.  Carefully  conducted  fasting  experiments  have  demonstrated 
this.  A  dog  nourished  on  an  ordinary  diet  to  which  bone  ash  has  been 
added  will  excrete  grey  feces.  When  fasted  such  an  animal  will,  after 
a  few  days,  excrete  a  small  amount  of  a  greenish-brown  mass,  containing 
no  bone  ash.  These  sue  fasting  feces.  They  are  of  a  pi  tch-Hke  consistency 
and  turn  black  on  contact  with  the  air.7  Adult  fasting  men  have  been 
found  to  excrete  7-8  grams  of  feces  per  day,  the  daily  nitrogen 
value  being  about  o.i  gram.8  No  separating  medium  such  as 

1Cammidge:  The  Feces  of -Children  and  Adults,  1914,  p.  126. 

'Kermauner:  Zeit.  ftir  B iol.,  35,  316,  1897. 

•Foster  and  Hawk:  Jour.  Am.  Chem.  Soc.,  37,  1347,  1915. 

4  The  percentage  of  the  ingested  protein  which  is  absorbed  from  the  intestine.  To 
calculate  this  factor  subtract  the  metabolic  nitrogen  from  the  total  fecal  nitrogen  and 
then  subtract  this  value  from  the  food  nitrogen  and  divide  by  the  food  nitrogen. 
(See  "Protein  Utilization,"  p.  590.) 

'Tsuboi:  Zeit.  fur  Biol.,  35,  68,  1897;  Mendel  and  Fine:  Jour.  Biol.  Chem.,  n,  5, 1912. 

6Myers  and  Fine:  Proc.  Soc.  Exp.  Biol.  and  Med.,  16,  73,  1919. 

7  Howe  and  Hawk:  Jour.  Am.  Chem.  Soc.,  33,  215,  1911. 

8  Howe,  Mattill  and  Hawk:  Ibid.,  33,  568,  1911. 


FECES  231 

charcoal  or  carmine  (page  227)  should  be  used  in  differentiating 
fasting  feces. 

In  recent  years  the  examination  of  feces  for  evidences  of  parasitism 
(detection  of  parasites  and  their  ova)  has  taken  on  an  added  importance. 
The  investigation  of  the  hookworm  has  been  particularly  developed. 
(For  methods  and  discussion  see  Bulletin  135,  Bureau  of  Animal  Indus- 
try, U.S.  Department  of  Agriculture,  1911,  M.  C.  Hall.) 

For  diagnostic  purposes  the  macroscopical  and  microscopical  exami- 
nations of  the  feces  ordinarily  yield  much  more  satisfactory  data  than 
are  secured  from  its  chemical  examination.  Possibly  with  the  excep- 
tion of  certain  examinations  for  occult  blood,  the  most  satisfactory  data 
for  diagnostic  purposes  are  secured  by  microscopical  examination. 
This  presupposes  a  knowledge  of  microscopical  technic  and  the  use  of 
certain  microchemical  tests,  by  which  much  information  can  be  ob- 
tained. The  principle  underlying  this  examination  consists  in  the  study 
of  the  actual  changes  which  the  various  food-stuffs  have  undergone  dur- 
ing digestion.  A  knowledge  of  the  changes  which  occur  in  normal  diges- 
tion and  which  are  seen  in  normal  feces  enables  one  to  readily  detect 
pathological  variations.  One  diet  widely  used  for  this  purpose  is  the 
Schmidt  diet  which  is  given  below.  The  modification1  described  is 
better  adapted  to  American  conditions 

The  Schmidt  intestinal  diet  is  as  follows : 

In  the  morning:  0.5  liter  of  milk,  or  if  milk  does  not  agree  0.5  liter 
of  cocoa  (prepared  from  20  grams  of  cocoa  powder,  10  grams  sugar, 
400  grams  water,  and  100  grams  milk) .  To  this  add  50  grams  zwiebach. 

In  the  forenoon:  0.5  liter  oatmeal  gruel  (made  from  40  grams  oat- 
meal), 10  grams  butter,  100  grams  milk,  300  grams  water,  i  egg  strained. 

At  noon:  125  grams  of  chopped  beef  (raw  weight)  broiled  rare  with 
20  grams  of  butter,  so  that  the  interior  will  remain  raw.  To  this  add 
250  grams  potato  broth  (made  of  190  grams  mashed  potatoes,  100  grams 
milk,  10  grams  of  butter). 

In  the  afternoon:  as  in  the  morning. 

In  the  evening:  as  in  the  forenoon. 

This  diet  necessitates  five  meals  a  day  especially  prepared  and  does 
not  follow  the  average  American  dietary.  In  simple  microscopical 
examinations  for  food  digestion,  the  following  diet  as  more  closely 
approximating  the  ordinary  dietary  regime  is  suggested.  Should 
chemical  determinations  for  fat  be  desired  all  fat  containing  foods  can 
be  eliminated  except  those  in  which  its  specific  content  is  known  and  a 
measured  amount  of  fat  given.  The  feces  can  then  be  separated  by 
means  of  carmine. 

1  Used  by  Dr.  Rehfuss  at  Jefferson  Hospital. 


232 


PHYSIOLOGICAL   CHEMISTRY 


Modified  Schmidt  Diet 
Breakfast: 

100  grams  cream  of  wheat  or  oatmeal 
60  grams  toast 
20  grams  butter 
250  c.c.  milk. 

Luncheon: 

Rice  soup  (chicken  broth  with  rice) 
100  grams  green  vegetable  (asparagus) 
100  grams  mashed  potato 

60  grams  toast 

20  grams  butter 
250  c.c.  milk. 

4  o'clock : 

250  c.c.  of  milk. 

Dinner: 

150  grams  of  chopped  meat,  grilled  on  the  outside  and  rare  in  the  center 
100  grams  green  vegetable  (spinach) 
100  grams  mashed  potatoes 
60  grams  of  toast 
20  grams  of  butter 
250  c.c.  milk 
Stewed  fruit. 

EXPERIMENTS  ON  FECES 

i.  Macroscopical  Examination. — If  the  stool  is  watery  pour  it  into  a  shallow 
dish  and  examine  directly.  If  it  is  firm  or  pasty  it  should  be  treated  with  water 
and  carefully  stirred  before  the  examination  for  macroscopical  constituents  is 
attempted.  The  macroscopical  constituents  may  be  collected  very  satisfactorily 
by  means  of  a  double  layer  of  cheese  cloth. 

A  Boas  sieve  (Fig.  69)  may  also  be  used  to  collect  the  macroscopical 
constituents  of  feces.  This  sieve  is  constructed  of  two  easily  detachable 
hemispheres  which  are  held  together  by  means  of  a 
bayonet  catch.  In  using  the  apparatus  the  feces  are 
spread  out  upon  a  very  fine  sieve  contained  in  the 
lower  hemisphere  and  a  stream  of  water  is  allowed  to 
play  upon  it  through  the  medium  of  an  opening  in 
the  upper  hemisphere.  The  apparatus  is  provided 
with  an  orifice  in  the  upper  hemisphere  through 
which  the.  feces  may  be  stirred  by  means  of  a  glass 
rod  during  the  washing  process.  After  1 5-30  minutes 
washing  nothing  but  the  coarse  fecal  constituents 
remain  upon  the  sieve. 


FIG. 


6Q. — BOAS 
SIEVE. 


2.  Microscopical  Examination.— After  the  ingestion  of 
the  test  diet  (see  Schmidt  diet  above)  for  several  days,  a 
specimen  of  the  movement  is  collected.  Any  gross  abnor- 
malities are  recorded  hi  the  form,  consistence,  and  char- 
acter of  the  stool  as  well  as  the  admixture  of  certain  pathological  elements 
such  as  pus,  blood,  mucus,  and  parasites.  The  movement  is  then  rubbed  out 
on  plates  and  the  presence  of  undigested  food-stuffs  sought  for.  Normally  the 
test  diet  is  almost  completely  digested  and  no  gross  undigested  material  is 
found.  Therefore  the  presence  of  these  macroscopic  rests  is  in  itself  evidence 


FECES 


of  disturbed  digestion.  Clean  slides  and  cover-glasses  are  then  prepared 
and  a  small  representative  portion  of  the  movement  is  placed  on  each  of  three 
slides.  The  routine  clinical  method  of  examination  follows :  To  the  first  slide 
is  added  a  drop  of  distilled  water  and  it  is  then  examined  with  low  and  high 
powers.  ,  . 


FIG.  70. — A,  intact  undigested  meat 
fibers;  J5,  partially  digested  meat  fibers; 
C,  almost  completely  digested  meat 
fibers. 


FIG.  71. — A,  neutral  fat;  B,  fatty  acid 
liberated  by  acetic  acid;  C,  soaps;  D,  fatty 
acid  crystals. 


FIG.  72. — A,  elastic  tissue;  B,  white  FIG.  73. — A,  cellulose  remains  of  vege- 

fibrous    tissue    (macroscopic);    C,    white         tables;    B,    empty   potato   cells;    C,    potato 
fibrous  tissue  (microscopic.)  cells    filled    with   starch,    and   stained    with 

iodine;  D,  hard  cells  found  in  pears;  E,  spiral 
and  woody  fibers  from  pith  of  vegetables; 
F,  vegetable  hairs. 
FIGS.  70  TO  73. — MICROSCOPICAL  CONSTITUENTS  OF  FECES. 

Meat  fibers  are  readily  recognized  by  their  yellowish  hyaline .  ap- 
pearance possibly  with  a  few  striae  still  visible  in  the.  fibers.  Should 
meat  fibers  be  found  bound  together  by  connective  tissue  or  raw 
connective  tissue,  either  white  fibrous  or  yellow  elastic,  be  noted,  it 


234 


PHYSIOLOGICAL  CHEMISTRY 


indicates  a  disturbance  of  gastric  function  inasmuch  as  one  of  the  spe- 
cific functions  of  the  gastric  juice  is  to  dissolve  the  intercellular  tissue 
binding  together  the  fibers.  If  large  numbers  of  meat  fibers  are  found 
after  a  tes;t  diet,  particularly  if  the  nuclei  are  still  intact  in  the  fibers, 
the  inference  of  poor  or  low  pancreatic  function  is  justifiable.  This 
is  true  if  it  can  be  demonstrated  that  the  food  has  been  sufficiently 
long  in  its  transit  through  the  intestinal  tract  to  permit  the  pancreatic 
enzymes  to  carry  on  their  work.  A  dilute  solution  of  methylene  blue 
will  readily  show  the  nuclei  if  present. 

The  second  slide  is  examined  for  fats  and  then  treated  with  acetic  acid  and 
heated  to  split  any  soaps  which  may  be  present  and  form  fatty  acid. 

Fats  are  met  with  in  three  forms  (a)  neutral  fats  readily  demonstrated  by 
Sudan  HI,  Scharlach  R  or  Osmic  acid;  (b)  fatty  acids  which  are  usually  found  in 
the  form  of  needle-like  crystals  soluble  in  ether,  alcohol,  and  solutions  of  sodium 


FIG.  74. — A,  calcium  sulphate  crys- 
tals; B,  cholesterol  crystals;  C,  char- 
coal detritus;  D,  bismuth  sub-oxide 
crystals;  E,  calcium  oxalate  crystals. 


FIG.  75. — A,  Schmidt  test  bag  for  study 
of  pancreatic  function;  B,  nuclei  of  meat 
fibers  digested;  C,  nuclei  of  meat  fibers 
undigested;  D,  undigested  stained  thymus 
cells. 


FIGS.  74  AND  75.— MICROSCOPICAL  CONSTITUENTS  OF  FECES. 

hydrate  (these  crystals  do  not  stain  with  Sudan  HI  but  form  drops  on  being 
warmed) ;  (c)  soaps  are  usually  found  in  the  feces  either  as  amorphous  flakes  or 
scallop  shell-like  formations,  but  may  occasionally  occur  in  crystalline  form. 
The  calcium  soaps  which  compose  the  bulk  of  the  soaps  in  the  feces  can  be  dis- 
tinguished from  the  potassium  and  sodium  compounds  because  of  their  insolu- 
bility in  hot  water,  alcohol,  and  ether.  On  heating  with  30  per  cent  acetic  acid, 
fatty  acids  are  set  free  in  drops  which  crystallize  out  on  cooling. 

The  estimation  of  fats  is  a  rather  important  matter  and  the  trained 
observer  can  usually  detect  disturbances  in  fat  digestion.  Normally 
there  are  fats  present  in  the  movement,  but  abnormally  their  quantity 
is  relatively  increased  either  in  total  fat,  or  in  one  of  its  components. 


FECES  235 

While  it  is  true  that  bacterial  activity  plays  a  considerable  r61e  in  the 
digestion  of  fats,  a  marked  increase  in  fat  usually  indicates  pancreatic 
disease,  or  a  disturbance  in  pancreatic  function,  This  is,  of  course,  the 
case  only  when  the  amount  of  fat  ingested  is  not  in  excess  of  that  which 
can  be  readily  handled  under  normal  conditions.  In  cases  of  pure 
biliary  obstruction  without  pancreatic  involvement,  fat-splitting  takes 
place  in  a  normal  way,  but  the  fatty  acids  and  soaps  formed  are  not 
absorbed  owing  to  the  absence  of  bile.  Such  a  movement  is  full  of 
soaps  and  fatty  acid  crystals  which  on  treatment  with  acetic  acid  show 
a  marked  increase  in  total  fat  over  normal.  Failure  of  absorption 
owing  to  extensive  disease  of  the  intestinal  mucosa  can  produce  a  similar 
picture  but  will  usually  give  some  cytological  evidence  of  intestinal 
disease.  Pure  pancreatic  disease  gives  a  marked  increase  in  total  and 
neutral  fat  with  the  presence  of  bile. 

Undigested  starches  are  readily  recognized  by  their  blue  reaction  with  iodine. 
This  can  be  studied  on  the  third  slide. 

This  phenomenon  is  the  least  frequent  among  the  different  forms  of 
pathological  digestion  and  usually  indicates  food  bolting,  an  excessive 
ingestion  of,  or  poor  preparation  of  carbohydrate  food,  or  an  infection 
of  the  bowel  with  so-called  "garungsdyspepsia"  rather  than  an  actual 
disturbance  of  pancreatic  function  inasmuch  as  the  amylolytic  function 
of  the  pancreas  is  the  most  persistent  and  the  last  to  disappear. 

Disturbance  in  cellulose  digestion,  the  presence  of  blood,  leucocytes, 
mucus,  etc.,  can  all  be  demonstrated  by  appropriate  technicand  represent 
a  chapter  in  the  study  of  the  feces  of  great  diagnostic  importance,  but 
one  which  is  beyond  the  province  of  this  volume.  (For  further  discus- 
sion, see  page  231.  For  cuts  of  fecal  constituents  found  microscopic- 
ally, see  pages  233  and  234.) 

3.  Reaction. — Thoroughly  mix  the  feces  and  apply  moist  red  and  blue  litmus 
papers  to  the  surface.    If  the  stool  is  hard  it  should  be  mixed  with  water  before 
the  reaction  is  taken.    Examine  the  stool  as  soon  after  defecation  as  is  conven- 
ient, since  the  reaction  may  change  very  rapidly.    The  reaction  of  the  normal 
stools  of  adult  man  is  ordinarily  neutral  or  faintly  alkaline  to  litmus,  but  seldom 
acid.    Infants'  stools  are  generally  acid  in  reaction.    Try  the  reaction  to  Congo 
red  paper.    Also  test  the  reaction  of  fecal  extract  to  phenolphthalein. 

4.  Starch.— If   any  imperfectly  cooked    starch-containing   food  has  been 
ingested  it  will  be  possible  to  detect  starch  granules  by  a  microscopical  examina- 
tion of  the  feces.    If  the  granules  are  not  detected  by  a  microscopical  examina- 
tion, the  feces  should  be  placed  in  an  evaporating  dish  or  casserole  and  boiled 
with  water  for  a  few  minutes.    Filter  and  test  the  filtrate  by  the  iodine  test  in  the 
usual  way  (see  page  43). 

5.  Cholesterol,  Koprosterol  and  Fat. — Introduce  about  5  grams  of  moist 
feces  into  a  100  c.c.  glass-stoppered  cylinder.    Add  30  c.c.  of  distilled  water  and 
25  c.c.  of  ether,  then  stopper  the  cylinder  and  shake  vigorously  for  five  minutes. 


236  PHYSIOLOGICAL   CHEMISTRY 

Allow  to  separate,  pour  or  pipette  off  the  ethereal  solution.  Filter  and  remove  the 
ether  by  evaporation.  The  residue  contains  cholesterol  and  the  mixed  fats  of 
the  feces.  For  every  gram  of  fat  add  about  1.5  grams  of  solid  potassium  hy- 
droxide and  25  c.c.  of  95  per  cent  alcohol  and  boil  in  a  flask  on  a  water-bath  for 
one-half  hour,  maintaining  the  volume  of  alcohol  constant.  This  alcoholic- 
potash  has  saponified  the  mixed  fats  and  we  now  have  a  mixture  of  soaps, 
cholesterol  and  koprosterol.  Add  sodium  chloride,  in  substance,  to  the  mixture 
and  extract  with  ether  to  dissolve  out  the  cholesterol  and  koprosterol.  Remove 
the  ether  by  evaporation  and  examine  the  residue  microscopically  for  cholesterol 
and  koprosterol  crystals.  Try  any  of  the  other  tests  for  cholesterol  as  given  on 
page  212. 

6.  Blood. — Undecomposed  blood  may  be  detected  macroscopically. 
If  uncertain,  look  for  erythrocytes  under  the  microscope,  and  spectro- 
scopically  for  the  spectrum  of  oxyhemoglobin  (see  Absorption  Spectra, 
Plate  I). 

In  case  the  blood  has  been  altered  or  is  present  in  minute  amount 
("occult  blood")?  and  cannot  be  detected  by  the  means  just  mentioned, 
the  following  tests  may  be  tried: 

(a)  Benzidine  Reaction. — Make  a  thin  fecal  suspension  using  about  5  c.c.  of 
distilled  water,  and  heat  it  to  boiling  to  render  oxidizing  enzymes  inactive. 
To  2  c.c.  of  a  saturated  solution  of  benzidine  in  glacial  acetic  acid  add  3  c.c.  of 
3  per  cent  hydrogen  peroxide  and  2-3  drops  of  the  cooled  fecal  suspension. 
A  clear  blue  color  appears  within  one  to  two  minutes  in  the  presence  of  blood. 
If  the  mixture  is  not  shaken  a  ring  of  color  will  form  at  the  top.    Minute  traces  of 
blood  are  more  easily  detected  by  the  latter  procedure. 

Wagner1  has  simplified  the  benzidin  test  so  that  it  can  be  applied 
much  more  conveniently. 

Slide  Modification. — Take  up  a  little  of  the  solid  stool  on  a  match,  smear  it 
on  an  object  glass  and  pour  the  reagent  over  it.  It  turns  blue  if  there  is  blood 
present  and  there  is  no  misleading  green  tint  from  fluid.  Make  the  solution 
as  follows:  Add  a  knife-tip  of  benzidine  to  2  c.c.  of  glacial  acetic  acid,  and 
add  20  drops  of  a  3  per  cent  solution  of  hydrogen  peroxide. 

By  this  dry  technic  there  is  no  danger  of  soiling  the  fingers,  and  the 
test  is  more  sensitive  than  the  usual  "wet"  benzidine  test.  The  smear 
of  stool  is  either  blue  or  it  is  not  blue.  The  rapidity  of  the  color  change 
gives  some  idea  as  to  the  proportion  of  blood  in  the  stool;  with  much 
blood  present  the  change  to  blue  is  instantaneous.  It  is  claimed  by 
Vaughn2  that  pus  and  the  usual  drugs  and  foods  ingested  do  not 
interfere  with  the  reaction. 

(b)  Lyle-Curtman  Guaiac  Procedure.3 — Approximately  10  gm.  of  the  stool 
are  transferred  to  a  beaker,  25  c-.c.  of  distilled  water  are  added,  and  the  mixture 
is  stirred  until  of  uniform  consistency.     Over  a  low  flame,  the  mixture  is  heated 

1  Wagner:  Zentbl.fur  Chirurgie,  41,  No.  28,  1914. 

2  Vaughn:  Jour,  of  Lab.,  Clin.  Med.,  2,  437,  1917. 
3Lyle  and  Curtman:  Jour.  Biol.  Chem.,  33,  i,  1918. 


FECES  237 

with  constant  stirring  to  boiling  and  kept  at  the  boiling  temperature  for  several 
minutes.  After  cooling,  one-half  of  the  mixture  is  transferred  to  a  glass- 
stoppered  bottle  of  80  c.c.  capacity,  5  c.c.  of  glacial  acetic  acid  and  25  c.c.  of 
ether  are  added,  and  the  mixture  is  thoroughly  shaken  and  allowed  to  stand  for 
several  minutes.  In  a  test  tube,  2  c.c.  of  the  ether  extract  are  treated  with 
0.5  c.c.  (i  :6o)  of  the  Lyle-Curtman  guaiac  reagent1  and  finally  one  to  five  drops 
of  30  per  cent  perhydrol  are  added  slowly  from  a  pipette.  A  decided  green,  light 
or  dark  blue,  or  purple  color  indicates  the  presence  of  blood  in  quantity  to  be  of 
clinical  significance. 

,  (c)  Ortho-tolidin  Test  (Ruttan  and  Hardisty)2—  To  i  c.c.  of  a  4  per  cent 
glacial  acetic  acid  solution  of  o-tolidin3  in  a  test-tube  add  i  c.c.  of  the  solution 
under  examination  and  i  c.c.  of  3  per  cent  hydrogen  peroxide.  In  the  presence 
of  blood  a  bluish  color  develops  (sometimes  rather  slowly)  and  persists  for 
some  time  (several  hours  in  some  instances). 

This  test  is  said  to  be  as  sensitive  for  the  detection  of  occult  blood  in 
feces  and  stomach  contents  as  is  the  benzidine  reaction.  It  is  also 
claimed  to  be  more  satisfactory  for  urine  than  any  other  blood  test. 
The  acetic  acid  solution  may  be  kept  for  one  month  with  no  reduction 
in  delicacy. 

(d)  Phenolphthalein  Test.4'  —  Make  a  thin  fecal  suspension  using  about  5  c.c.  of 
distilled  water.  Heat  to  boiling,5  cool  and  add  2  c.c.  of  the  suspension  to  i  c.c.  of 

1  The  Lyle-Curtman  Guaiac  Reagent.  —  Fifty  gm.  of  the  ground  crude  gum  guaiac  are 
treated  in  a  beaker  with  20  gm.  of  KOH  dissolved  in  200  c.c.  of  water.  After  thorough 
stirring,  the  mixture  is  filtered  with  the  aid  of  suction  through  cotton  spread  out  in  a  thin 
layer  in  a  Buchner  funnel.  The  residue  is  washed  with  water  until  the  combined  filtrate 
and  washings  approximate  1.5  liters.  To  the  diluted  KOH  solution  are  added  with  con- 
stant stirring  21  c.c.  of  glacial  acetic  acid  which  is  run  dropwise  from  a  burette.  The 
precipitate  is  allowed  to  settle,  the  supernatant  liquid  poured  off,  and  the  residue  washed 
once  with  water  by  decantation.  The  precipitate  is  then  transferred  to  a  Buchner  funnel 
and  dried  by  suction  as  much  as  possible.  The  precipitate  is  gently  heated  (small  portions 
at  a  time)  in  an  evaporating  dish  when  most  of  the  water  separates  and  is  removed  by 
filter  paper.  After  the  removal  of  the  water,  and  while  the  mass  is  still  plastic,  it  is  drawn 
out  into  thin  sheets.  In  this  condition  the  material  rapidly  hardens  and  dries  in  the  air. 
The  dried  masses  are  then  ground,  treated  with  300  c.c.  of  hot  95  per  cent  alcohol  and  the 
mixture  is  thoroughly  stirred  to  prevent  the  formation  of  a  gummy  mass.  In  a  few  min- 
utes a  dark  brown  material  separates  in  a  flocculent  condition.  This  is  filtered,  off  and  the 
alcohol  removed  from  the  solution  by  distillation.  The  residue  in  the  flask  is  treated 
with  20  gm.  of  KOH  dissolved  in  water,  diluted  considerably,  and  precipitated  as  before 
with  about  20  c.c.  of  glacial  acetic  acid.  The  precipitate  is  filtered  off  and  dried  as  de- 
scribed above,  after  which  it  is  ground  and  kept  in  a  desiccator.  The  weight  of  the  material 
finally  obtained  represents  a  yield  of  about  60  per  cent.  The  time  required  to  make  this 
preparation  is  4  hours,  the  distillation  of  the  alcohol  being  the  most  time-consuming  of  all 
the  operations. 

A  solution  containing  i  gm.  of  this  preparation  in  60  c.c.  of  95  per  cent  alcohol  may  be 
prepared  and  kept  in  a  glass-stoppered  bottle  of  colorless  glass.  This  reagent  does  not 
deteriorate  for  several  weeks. 

2Ruttan  and  Hardisty:  Canadian  Medical  Ass'n  Journal,  Nov.,  1912,  also  Biochemical 
Bull.,  2,  225,  1913. 

3NH2  NH, 


CH3  CH3 

4  Boas:  Deut.  med.  Woch.,  37,  62,  1911. 

5  Boas  suggests  using  an  ether  extract  of  the  fecal  suspension  thus  eliminating  the 
necessity  of  boiling.     However,  oxidizing  enzymes  are  the  main  sources  of  error  here  and  the 
action  is  easily  and  effectively  eliminated  by  boiling.     (See  White:  Boston  Medical  and 
Surgical  Journal,  164,  876,  1911.) 


238  PHYSIOLOGICAL  CHEMISTRY 

the  phenolphthalein  reagent1  and  a  few  drops  of  hydrogen  peroxide.     A  pink  or 
red  color  promptly  forms  in  the  presence  of  blood. 

Schirokauer2  makes  the  statement  that  a  mixture  of  alcohol  and  glacial  acetic 
acid  will  give  the  phenolphthalein  reaction  for  occult  blood.  The  action  of  an  oxi- 
dizing agent  will  make  this  reaction  more  distinct.  Von  Czylharz  and  Neustadl3 
find  that  a  solution  of  sodium  salicylate  added  to  a  blood-free  extract  of  feces  will 
give  a  very  deceptive  reaction,  while  feces  after  the  administration  of  sodium 
salicylate  by  mouth  gave  the  same  reaction.  The  same  was  true  of  acetyl  salicylic 
acid  and  other  similar  drugs.  Their  studies  in  clinical  cases  likewise  indicated  that 
the  phenolphthalein  test  was  unreliable. 

(e)  Hematein  Reaction  for  Occult  Blood. — Couturi  er4  advises  the  use  of 
hematein5  in  testing  for  occult  blood.     It  is  only  slightly  soluble  in  water, 
but  gives  a  pronounced  red  color.     In  contact  with  sodium  hydroxide 
this  red  solution  turns  a  deep  violet  blue,  giving  an  insoluble  compound 
of  hematein  and  sodium.     This  compound,  exposed  to  the  air  oxidizes 
after  several  days,  and  gives  brownish  or  yellowish  compounds,  depend- 
ing on  dilution.     This  change  is  only  hastened  a  little  by  the  addition 
of  hydrogen  peroxide,  but  if  a  trace  of  blood  is  added  to  the  hydrogen 
peroxide,  it  takes  place  almost  instantly.     To  avoid  oxidation,  the  hem- 
atein sodium  mixture  should  be  prepared  just  before  use.     Three  fluids 
are  required:  (i)  a  0.05  per  cent  aqueous  solution  of  hematein;  (2)  a 
40  per  cent  solution  of  sodium  hydroxide  and  (3)  3  per  cent  hydrogen 
peroxide.     These  will  keep  almost  indefinitely.  *^"" 

The  test  may  be  perf ormed  as  follows :  Take  4-5  c.c.  of  the  liquid  specimen  in  a 
tube  and  in  another  tube  take  the  same  amount  of  material  known  not  to  contain 
blood  as  a  control.  To  each  add  4-5  c.c.  of  the  sodium  hydroxide  solution  and 
shake.  Then  to  each  of  the  tubes  add  2  drops  of  the  hematein  solution.  A  blue 
color  of  about  equal  intensity  will  develop  in  both  tubes.  Then  add  10  drops  of 
hydrogen  peroxide  to  each  tube  and  compare.  If  blood  is  present,  the  tube  con- 
taining it  will  turn  very  rapidly  (in  three  or  four  seconds)  to  violet  red,  then  in 
twenty  seconds  to  clear  brown,  in  forty  seconds  to  pale  yellow  while  the  second 
tube  will  not  show  these  changes  for  several  minutes.  The  reaction  is  said  to 
detect  blood  when  present  in  a  concentration  of  i  part  in  400,000. 

(f )  Cowie's  Guaiac  Test. — To  i  gram  of  moist  feces  add  4-5  c.c.  of  glacial  ace- 
tic acid  and  extract  the  mixture  with  30  c.c.  of  ether.    To  1-2  c.c.  of  the  extract 
add  an  equal  volume  of  water,  agitate  the  mixture,  introduce  a  few  granules  of 
powdered  guaiac  resin,  and  after  bringing  the  resin  into  solution,  gradually  add 
30  drops  df  old  turpentine  or  hydrogen  peroxide.    A  blue  cplor  indicates  the 

1  Prepared  by  dissolving  1-2  grams  of  phenolphthalein  and  25  grams  of  KOH  in  100  c.c. 
of  distilled  water.  Add  i  gram  of  powdered  zinc  and  heat  gently  until  the  solution  is 
decolorized.  Prepared  in  this  way  the  solution  will  not  deteriorate  on  standing. 

2Deutsch.  med.  Woch.,  Aug.  6,  1914. 

1  Wien.  med.  Woch.^  Sept.  5,  1914. 

4Lyon  Med.,  46,  313,  1914. 

6  Hematein  is  a  brownish-red  crystalline  substance  derived  from  hematoxylin  by  the 
successive  action  of  ammonia  and  acetic  acid.  It  should  not  be  confused  with  hematin, 
the  hemoglobin  derivative. 


FECES  239 

presence  of  blood.    Cowie  claims  that  by  means  of  this  test  an  intestinal  hemor- 
rhage of  i  gram  can  easily  be  detected  by  an  examination  of  the  feces. 

7.  Hydrobilirubin.    Schmidt's  Test. — Rub  up  a  small  amount  of  feces  in  a 
mortar  with  a  concentrated  aqueous  solution  of  mercuric  chloride.    Transfer  to  a 
shallow,  flat-bottomed  dish  and  allow  to  stand  6-24  hours.    The  presence  of 
hydrobilirubin  will  be  indicated  by  a  deep  red  color  being  imparted  to  the  par- 
ticles of  feces  containing  this  pigment.    This  red  color  is  due  to  the  formation 
of  hydrobilirubin-mercury.    If  unaltered  bilirubin  is  present  in  any  portion  of 
the  feces  that  portion  will  be  green  in  color  due  to  the  oxidation  of  bilirubin  to 
biliverdin. 

Another  method  for  the  detection  of  hydrobilirubin  is  the  following:  Treat 
the  dry  feces  with  absolute  alcohol  acidified  with  sulphuric  acid  and  shake 
thoroughly.  The  acidified  alcohol  extracts  the  pigment  and  assumes  a  reddish 
color.  Examine  a  little  of  this  fluid  spectroscopically  and  note  the  typical 
spectrum  of  hydrobilirubin  (Absorption  Spectra,  Plate  II). 

8.  Bilirubin.1    (a)  Gmelin's  Test. — Place  a  few  drops  of  concentrated  nitric 
acid  in  an  evaporating  dish  or  on  a  porcelain  test-tablet  and  allow  a  few  drops  of 
the  feces  and  water  to  tni*  with  it.    The  usual  play  of  colors  of  Gmelin's 
test  is  produced,  i.e.,  green,  blue,  violet,  red,  and  yellow.    If  so  desired,  this 
test  may  be  executed  on  a  slide  and  observed  under  a  microscope. 

(b)  Huppert's  Test. — Treat  the  feces  with  water  to  form  a  semi-fluid  mass,  add 
an  equal  amount  of  milk  of  lime,  shake  thoroughly,  and  filter.  Wash  the  precipi- 
tate with  water,  then  transfer  both  the  paper  and  the  precipitate  to  a  small  beaker 
or  flask,  add  a  small  amount  of  95  per  cent  alcohol  acidified  slightly  with  sulphuric 
acid,  and  heat  to  boiling  on  a  water-bath.  The  presence  of  bilirubin  is  indicated 
by  the  alcohol  assuming  a  green  color. 

Steensma  advises  the  addition  of  a  drop  of  a  0.5  per  cent  solution  of  sodium 
nitrite  to  the  acid-alcohol  mixture  before  warming  on  the  water-bath.  Try  this 
modification  also. 

9.  Bile  Acids. — Extract  a  small  amount  of  feces  with  alcohol  and  filter. 
Evaporate  the  filtrate  on  a  water-bath  to  drive  off  the  alcohol  and  dissolve  the 
residue  in  water  made  slightly  alkaline  with  potassium  hydroxide.    Upon  this 
aqueous  solution  try  any  of  the  tests  for  bile  acids  given  on  page  211. 

10.  Casein. — Extract  the  fresh  feces  first  with  a  dilute  solution  of  sodium 
chloride,  and  later  with  water  acidified  with  dilute  acetic  acid,  to  remove  soluble 
proteins.     Now  extract  the  feces  with  0.5  per  cent  sodium  carbonate  and  filter. 
Add  dilute  acetic  acid  to  the  filtrate  to  precipitate  the  casein,  being  careful 
not  to  add  an  excess  of  the  reagent  as  the  casein  would  dissolve.     Filter  off  the 
casein  and  test  it  according  to  directions  given  on  page  339.     Casein  is  found 
principally  in  the  feces  of  children  who  have  been  fed  a  milk  diet.     Mucin  would 
also  be  extracted  by  the  dilute  alkali,  if  present  in  the  feces.    What  test  could 
you  make  on  the  newly  precipitated  body  to  differentiate  between  mucin  and 
casein? 

11.  Nucleoprotein. — Mix  the  stool  thoroughly  with  water,  transfer  to  a  flask, 
and  add  an  equal  amount  of  saturated  lime  water.     Shake  frequently  for  a  few 
hours,  filter,  and  precipitate  the  nucleoprotein  with  acetic  acid.     Filter  off  this 
precipitate  and  test  it  as  follows: 

1  The  detection  of  bilirubin  in  the  feces  is  comparatively  simple  provided  it  is  not  ac- 
companied by  other  pigments.  When  other  pigments  are  present,  however,  it  is  difficult  to 
detect  the  bilirubin  and,  at  times,  may  be  found  impossible. 


240  PHYSIOLOGICAL   CHEMISTRY 

(a)  Phosphorus. — Test  for  phosphorus  by  fusion  (see  page  128). 

(b)  Solubility. — Try  the  solubility  in  the  ordinary  solvents. 

(c)  Protein  Color  Test. — Try  any  of  the  protein  color  tests. 

What  proof  have  you  that  the  above  body  was  not  mucin?     What  other  test 
can  you  use  to  differentiate  between  nucleoprotein  and  mucin? 

12.  Albumin  and  Globulin. — Extract  the  fresh  feces  with  a  dilute  solution  of 
sodium  chloride.     (The  preliminary  extract  from  the  preparation  of  casein  (10), 
above,  may  be  utilized  here.)     Filter,  and  saturate  a  portion  of  the  nitrate  with 
sodium  chloride  in  substance.     A  precipitate  signifies  globulin.     Filter  off  the  pre- 
cipitate and  acidify  the  nitrate  slightly  with  dilute  acetic  acid.     A  precipitate  at 
this  point  signifies  albumin.     Make  a  protein  color  test  on  each  of  these  bodies. 

13.  Proteose  and  Peptone. — Heat  to  boiling  the  portion  of  the  sodium  chloride 
extract  not  used  in  the  last  experiment.     Filter  off  the  coagulum,  if  any  forms. 
Acidify  the  filtrate  slightly  with  acetic  acid  and  saturate  with  sodium  chloride  in 
substance.     A  precipitate  here  indicates  proteose.     Filter  it  off  and  test  it  according 
to  directions  given  on  page  119.     Test  the  filtrate  for  peptone  by  the  biuret  test. 

14.  Inorganic  Constituents. — Incinerate  a  small  amount  of  feces  in  a  crucible 
and  dissolve  the  ash  in  a  small  volume  of  dilute  nitric  acid.     Dilute  with  water  and 
filter.     Make  the  following  tests  upon  the  clear  filtrate. 

(a)  Chlorides. — Acidify  with  nitric  acid  and  add  silver  nitrate. 

(b)  Phosphates. — Acidify  with  nitric  acid,  add  molybdic  solution,  and  warm 
gently. 

(c)  Sulphates. — Acidify  with  hydrochloric  acid,  add  barium  chloride,  and  warm. 

(d)  Calcium. — Neutralize  with  ammonium  hydroxide,  make  slightly  acid  with 
acetic  acid  and  add  ammonium  oxalate.    Let  stand. 

(e)  Magnesium. — Neutralize  with  ammonium  hydroxide,  and  add  Na2HPO4 
and  excess  of  NH40H.    Let  stand. 

15.  Indole  Reactions. — Rub  up  the  stool  with  water  to  form  a  thin  paste 
and  distill  first  in  alkaline  and  then  in  acid  solution.    Test  the  distillate  by  any 
of  the  tests  for  the  detection  of  indole  hi  putrefaction  mixtures  (see  page  221 ). 

1 6.  Schmidt' s  Nuclei  Test. — This  test  serves  as  an  aid  to  the  diag- 
nosis of  pancreatic  insufficiency.     The  test  is  founded  upon  the  theory 
that  cell  nuclei  are  digestible  only  in  pancreatic  juice,  and  therefore 
that  the  appearance  in  the  feces  of  such  nuclei  indicates  insufficiency  of 
pancreatic  secretion. 

The  procedure  is  as  follows :  Cubes  of  fresh  beef  about  0.5  cm.  square  are 
enclosed  in  small  gauze  bags  and  ingested  with  a  test  meal.  Subsequently  the 
fecal  mass  resulting  from  this  test  meal  is  examined,  the  bag  opened,  and 
the  condition  of  the  enclosed  residue  determined.  Under  normal  conditions  the 
nuclei  would  be  digested.  Therefore  if  the  nuclei  are  found  to  be  for  the  most 
part  undigested,  and  the  intervening  period  has  been  sufficient  to  permit  of  the 
full  activity  of  the  pancreatic  function  (at  least  six  hours),  it  may  be  considered  a 
sign  of  pancreatic  insufficiency  (see  Fig.  75,  p.  234). 

It  has  been  claimed  by  Steele  that  under  certain  conditions  the  non- 
digestion  of  the  nuclei  may  indicate  a  general  lowering  of  the  digestive 
power  rather  than  a  true  pancreatic  insufficiency. 


FECES 


241 


Kashiwado1  has  suggested  the  use  of  stained  cell  nuclei  in  this  test. 
A  preparation  put  out  under  the  name  "  Gefarbte  gewebskerne  zur 
Pankreasfuntionspriifung  nach  Prof.  Dr.  Schmidt  und  Dr.  Kashiwado" 
consists  of  a  mixed  preparation  of  thymus  cells,  the  nuclei  of  which 
are  stained  by  iron  hematoxylin,  and  lycopodium  powder.  After 
administration,  the  lycopodium,  which  is  readily  recognized,  is  sought 
for  in  the  stool  and  when  found  that  portion  is  examined  for  the  stained 
thymus  cells.  Their  statement  is  as  follows:  If  stained  nuclei  are 
not  found  in  the  feces  after  an  intestinal  transit  of  sufficient  duration 
(at  least  six  hours)  normal  pancreatic  function  (external)  is  indicated. 
If,  however,  all  or  part  of  the  cells  are  found,  a  definite  disturbance  in 
pancreatic  function  is  present. 

17.  Influence  of  Drugs  upon  the  Color  of  the  "Stool. — Ingest  an  ordinary 
mixed  diet,  take  the  indicated  dose  of  one  of  the  following  drugs,  "separate" 
the  feces  (see  page  620)  and  after  the  "marker"  appears  note  the  color  of  the 
stools  evacuated : 


Drug 

Dose 

Color  of  stool 

Bismuth  subnitrate,  grams. 

5 

Black. 

Calomel,  mg. 

I3O—I4.O 

Green. 

Reduced  iron,  mg  

6"\—  70 

Grayish  black  turning  darker  on  exposure  to  air. 

Methylene  blue,  mg  

130—140 

Blue,  especially  after  exposure  to  air. 

Manganese  dioxide,  mg.  .  . 

130-140 

Dark  brown  or  black. 

Hematoxylin,  grams  

I 

Reddish  brown. 

Rhubarb,  c.c.  fluid  extract 

2 

Yellow. 

Senna,  c.c.  fluid  extract.  .  . 

4 

Dark  yellow. 

Cambogia,  mg.  . 

!•?  O—I4O 

Dark  yellow. 

Santonin  mg 

6<—  70 

Dark  yellow 

18.  Einhorn's  Bead  Test.2 — This  is  a  method  for  testing  the  digestive  func- 
tion. In  some  respects  it  is  similar  to  Sahli's  desmoid  reaction  (see  Gastric 
Analysis).  The  procedure  consists  in  wrapping  the  material  under  examination 
(catgut,  fish-bone,  raw  beef,  cooked  potatoes,  thymus  gland  or  mutton  fat,  etc.) 
in  gauze  to  which  glass  beads  of  various  colors  are  attached  and  enclosing  gauze 

1  Kashiwado:  Deut.  Arch.  Klin.  Med.,  104,  584,  1911. 

2Einhorn:  The  Post-Graduate,  May,  1912:  Boas'  Arch.,  12,  26,  1906;  13,  35,  i<)O7;Ibid., 
4755  15,  part  2,  1909. 

T6 


242  PHYSIOLOGICAL   CHEMISTRY 

* 

and  beads  in  a  gelatine  capsule.1  The  gelatine  capsule  is  swallowed  and  the 
beads  serve  to  facilitate  the  separation  of  the  gauze  from  the  feces.  The  residue 
within  the  gauze  is  then  examined.  If  beads  appear  in  much  less  than  24  hours 
an  accelerated  motility  is  indicated,  whereas  an  interval  of  48  hours  or  over 
elapsing  indicates  retarded  motility.  If  gastric  function  alone  is  to  be  studied 
silk  threads  are  attached  to  the  beads  and  the  latter  are  withdrawn  and  examined 
before  they  have  passed  into  the  intestine. 

19.  "Separation"  of  Feces. — In  order  to  become  familiar  with  the  method 
ordinarily  utilized  in  metabolism  experiments  to  differentiate  the  feces  which 
correspond  to  the  food  ingested  during  any  given  interval,  and  at  the  same  time 
to  secure  data  as  to  the  length  of  time  necessary  for  ingested  substances  to  pass 
through  the  alimentary  tract  proceed  as  follows :  Just  before  one  of  the  three 
meals  of  the  day  ingest  a  gelatine  capsule  (No.  oo)  containing  0.2-0.3  of  a  gram 
of  carmine  or  charcoal.    Make  an  inspection  of  all  stools  subsequently  dropped 
and  note  the  time  interval  elapsing  between  the  ingestion  of  the  capsule  and  the 
appearance  of  its  contents  hi  the  feces.    Under  normal  conditions  this  period  is 
ordinarily  24  hours.    This  test  is  thus  an  index  of  intestinal  motility. 

20.  Influence  of  Foods  upon  the  Color  of  the  Stool. — Ingest  a  diet  which 
contains  a  liberal  quantity  of  one  of  the  following  articles  of  diet,  "separate" 
the  feces  (page  620)  and  after  the  "marker"  appears  note  the  color  of  the  stools 
evacuated : 


Article  of  diet 

Color  of  stool 

Milk  

Light  yellow  or  grayish  white. 

Meat  

Brownish  black. 

Chlorophyllic  vegetables,  e.g.,  spinach  

Greenish. 

Non-chlorophyllic  vegetables  

Light  brown. 

Cherries  or  blackberries  

Reddish  brown. 

Cocoa  

Dark  red  or  chocolate  brown. 

Coffee... 

Dark  brown 

Corn  meal  

Light  colored. 

21.  Quantitative  Determination  of  Fecal  Amylase  (The  Author's2  Modification 
of  Wohlgemuth's3  Method). — Weigh  accurately  about  2  grams  of  fresh  feces  into 
a  mortar,4  add  8  c.c.  of  a  phosphate-chloride  solution  (o.i  mol  dihydrogen  sodium 
phosphate  a'nd  0.2  mol  disodium  hydrogen  phosphate  per  liter  of  i  per  cent  sodium 
chloride),  2  c.c.  at  a  time,  rubbing  the  feces  mixture  to  a  homogeneous  consistency 
after  each  addition  of  the  extraction  medium.  Permit  the  mixture  to  stand  at 
room  temperature  for  a  half-hour  with  frequent  stirring.  We  now  have  a  neutral 

1  Ordinarily  two  substances  are  attached  to  each  bead,  three  beads  tied  together  and 
enclosed  in  one  capsule.    Test  capsules  may  be  obtained  from  Eimer  and  Amend,  New  York. 

2  Hawk:  Arch.  Int.  Med.,  8,  552,  1911. 

•Wohlgemuth:  Berl.  klin.  Woch.,  47,  3,  92,  1910;  also  see  page  195,  this  book. 
4  Duplicate  determinations  should  be  made. 


FECES  243 

fecal  suspension.  Transfer  this  suspension  to  a  15  c.c.  graduated  centrifuge  tube, 
being  sure  to  wash  the  mortar  and  pestle  carefully  with  the  phosphate-chloride 
solution  and  add  all  washings  to  the  suspension  in  the  centrifuge  tube.  The  sus- 
pension is  now  made  up  to  the  15  c.c.  mark  with  the  phosphate-chloride  solution 
and  centrifugated  for  a  i5-minute  period,  or  longer  if  necessary,  to  secure  satis- 
factory sedimentation.  At  this  point,  read  and  record  the  height  of  the  sediment 
column.  Remove  the  supernatant  liquid  by  means  of  a  bent  pipette,  transfer  it  to 
a  50  c.c.  volumetric  flask  and  dilute  it  to  the  50  c.c.  mark  with  the  phosphate- 
chloride  solution.  Mix  the  fecal  extract  thoroughly  by  shaking  and  determine  its 
amylolytic  activity.  For  this  purpose  a  series  of  six  graduated  tubes  is  prepared1, 
containing  volumes  of  the  extract  ranging  from  2.5  c.c.  to  0.078  c.c.  Each  of  the 
intermediate  tubes  in  this  series  will  thus  contain  one-half  as  much  fluid  as  the 
preceding  tube.  Now  make  the  contents  of  each  tube  2.5  c.c.  by  means  of  the 
phosphate-chloride  solution  in  order  to  secure  a  uniform  electrolyte  concentration. 
Introduce  5  c.c.  of  a  i  per  cent  soluble  starch  solution1  and  three  drops  of  toluene 
into  each  tube,  thoroughly  mix  the  contents  by  shaking,  close  the  tubes  by  means 
of  stoppers  and  place  them  in  an  incubator  at  38°C.  for  24  hours.  At  the  end  of 
this  time  remove  the  tubes,  fill  each  to  within  half  an  inch  of  the  top  with  ice-water, 
add  i  drop  of  tenth-normal  iodin  solution,  thoroughly  mix  the  contents  and  examine 
the  tubes  carefully  with  the  aid  of  a  strong  light.  Select  the  last  tube  in  the  series 
which  shows  entire  absence  of  blue  color,  thus  indicating  that  the  starch  has  been 
completely  transformed  into  dextrin  and  sugar,  and  calculate  the  amylolytic  activity 
on  the  basis  of  this  dilution.  In  case  of  indecision  between  two  tubes,  add  an  extra 
drop  of  the  iodin  solution  and  observe  them  again.2 

The  amylolytic  value,  Df,  of  a  given  stool,  may  be  expressed  in  terms  of  i  c.c. 
of  the  sediment  obtained  by  centrifugation  as  above  described.  For  example,  if  it 
is  found  that  0.31  c.c.  of  the  phosphate-chloride  extract  of  the  stool  acting  at  38°C. 
for  24  hours  completely  transformed  the  starch  in  5  c.c.  of  a  i  per  cent  starch  solu- 
tion, then  we  would  have  the  following  proportion: 

0.31 :  5  (c.c.  starch  : :  i(c.c.  extract)  :X 

The  value  of  X  in  this  case  is  16.1,  which  means  that  i  c.c.  of  the  fecal  extract 
possesses  the  power  of  completely  digesting  16.1  c.c.  of  a  i  per  cent  starch  solution 
in  24  hours  at  38°C. 

1  In  preparing  the  i  per  cent  solution,  the  weighed  starch  powder  should  be  dissolved 
in  cold  distilled  water  in  a  casserole  and  stirred  until  a  homogeneous  suspension  is  obtained. 
The  mixture  should  then  be  heated  with  constant  stirring,  until  it  is  clear.     This  ordinarily 
takes  from  eight  to  ten  minutes.     A  slightly  opaque  solution  is  thus  obtained,  which 
should  be  cooled  and  made  up  to  the  proper  volume  before  using. 

2  Theoretically  we  would  expect  the  colors  to  range  from  a  light  yellow  to  a  dark  blue, 
with  red  tubes  holding  an  intermediate  position  in  the  series.    This  color  sequence  does 
often  occur,  but  its  occurrence  is  far  from  universal.     Many  times  the  first  tubes  in  the 
series,  i.e.,  those  containing  the  largest  quantities  of  the  fecal  extract,  will  exhibit  a  bluish 
cast  of  color  which  should  not  be  confused  with  the  starch  color  reaction.    When  these  blue 
tubes  are  present,  they  are  generally  followed  by  yellow,  red  and  blue  tubes  in  order,  the 
final  blue  tube,  of  course,  being  the  regulation  starch  reaction.     Occasionally  greenish  colors 
will  be  obtained  to  the  left  of  the  red  color.     It  also  sometimes  happens  that  it  is  somewhat 
difficult  to  determine  in  which  tube  to  the  right  of  the  red  color  the  starch  blue  color  is  first 
detected,  unless  the  tube  be  examined  carefully  before  a  strong  light.     In  every  instance, 
however,  when  these  blue  and  green  colors  are  observed,  it  is  noted  that  tubes  possessing  the 
true  dextrin  red  color  are  always  present  between  these  tubes  and  the  tubes  possessing  the 
true  starch  blue  color.     It  is  evident,  therefore,  that  these  bluish  tints  in  the  tubes  to  the 
left  of  the  dextrin  color  cannot  be  due  to  the  presence  of  starch.     The  cause  of  the  blue  color 
reaction  in  the  first  tubes  of  the  series  has  not  been  ascertained  as  yet. 


244  PHYSIOLOGICAL   CHEMISTRY 

Inasmuch  as  stools  vary  so  greatly  as  to  water  content,  it  is  essential  to  an 
accurate  comparison  of  stools  that  such  comparison  be  made  on  the  basis  of  the 
solid  matter.  Supposing,  for  example,  that  in  the  above  determination  we  had 
6.2  c.c.  of  sediment.  Since  the  supernatant  fluid  was  removed  and  made  up  to 
50  c.c.  before  testing  its  amylolytic  value,  it  is  evident  that  i  c.c.  of  this  sediment  is 
equivalent  to  8.1  c.c.  of  extract.  Therefore,  in  order  to  derive  the  amylolytic 
value  of  i  c.c.  of  sediment,  we  must  multiply  the  value  (16.1)  as  obtained  above 
for  the  extract,  by  8.1.  This  yields  130.4  and  enables  us  to  express  the  activity 
as  follows: 

Df32°;  =  130.4 

The  above  method  of  calculation  is  that  suggested  by  Wohlgemuth.  In  case  time 
and  facilities  permit  of  the  determination  of  the  moisture  content  of  the  feces,  it  is 
much  more  accurate  and  satisfactory  to  place  the  amylolytic  values  of  the  stools 
on  a  "  gram  of  dry  matter  "  basis.  The  amylolytic  values  of  the  stools  are  expressed 
as  the  number  of  cubic  centimeters  of  i  per  cent  starch  solution  which  the  amylase 
content  of  i  gram  of  dry  feces  is  capable  of  digesting. 

22.  Quantitative  Determination  of  Fecal  Bacteria.1 — The  method  is  a  simpli- 
fication of  MacNeal's  adaptation  of  the  Strasburger  procedure.2  About  2  grams  of 
feces  are  accurately  weighed  and  placed  in  a  50. c.c.  centrifuge  tube.  To  the  feces 
in  the  tube  a  few  drops  of  0.2  per  cent  hydrochloric  acid  are  added,  and  the  material 
is  mixed  to  a  smooth  paste  by  means  of  a  glass  rod.  Further  amounts  of  the  acid 
are  added  with  continued  crushing  and  stirring  until  the  material  is  thoroughly 
suspended.  The  tube  is  then  whirled  in  the  centrifuge  at  high  speed  for  one-half 
to  one  minute.  The  suspension  is  found  sedimented  into  more  or  less  definite  layers, 
the  uppermost  of  which  is  fairly  free  from  the  larger  particles.  The  upper  and 
more  liquid  portion  of  the  suspension  is  now  drawn  off  by  means  of  a  pipette  and 
transferred  to  a  beaker.3  The  sediment  remaining  in  the  tube  is  again  rubbed  up 
with  the  glass  rod  with  the  addition  of  further  amounts  of  dilute  acid,  and  again  cen- 
trifugalized  for  one-half  to  one  minute.  The  supernatant  liquid  is  pipetted  off  and 
added  to  the  first,  the  same  pipette  being  used  for  the  one  determination  through- 
out.4 A  third  portion  of  the  dilute  acid  is  then  added  to  the  sediment,  which  is 
again  mixed  by  stirring  and  again  centrifugalized.  All  the  washings  are  added  to 
the  first  one,  and  during  the  process  care  is  taken  to  wash  the  material  from  the 
walls  and  mouth  of  the  centrifuge  tube  down  into  it.  Finally,  when  the  sediment 
is  sufficiently  free  from  bacteria,  the  various  remaining  particles  are  visibly  clean, 
and  the  supernatant  liquid  after  centrifugalization  remains  almost  clear.  This  is 
removed  to  the  beaker  in  which  are  now  practically  all  the  bacteria  present  in  the 
original  portion  of  feces,  together  with  some  solid  matter  not  yet  separated.  In  the 
centrifuge  tubes  there  is  a  considerable  amount  of  bacteria-free  solid  matter. 

The  suspension  is  now  transferred  to  the  same  centrifuge  tube,  centrifugalized 
for  a  minute,  and  the  supernatant  liquid  transferred  to  a  clean  beaker  by  means  of 
the  same  pipette.  The  tube  is  then  refilled  from  the  first  beaker  and  thus  all  the 
suspension  centrifugalized  a  second  time.  The  beaker  is  finally  carefully  washed 

1Mattill  and  Hawk:  Jour.  Exp.  Med.,  14,  433,  1911. 

2  MacNeal,  Latzer  and  Kerr,  Jour.  Inf.  Dis.,  6,  123,  1909. 

3  A  25  c.c.  pipette  is  the  most  satisfactory  size;  to  facilitate  observation,  the  delivery  tube 
is  bent  near  the  bulb  to  an  angle  of  about  120  degrees. 

4  A  convenient  support  for  the  pipettes  is  a  wire  spring  on  a  glass  base,  such  as  is  used  on 
a  desk  for  pen-holders.     The  delivery  tube,  just  where  it  is  bent,  is  inserted  between  the 
wires,  and  any  liquid  not  delivered  collects  in  the  bend  of  the  tube. 


FECES  245 

with  the  aid  of  a  rubber-tipped  glass  rod,  the  second  sediment  in  the  centrifuge 
tube  is  washed  free  of  bacteria  by  means  of  this  wash  water  and  by  successive  por- 
tions of  the  dilute  acid,  and  the  supernatant  liquid  after  centrifugalization  is  added 
to  the  contents  of  the  second  beaker.  The  second  clean  sediment  is  added  to  the 
first.  The  bacterial  suspension  now  in  the  second  beaker  is  again  centrifugalized 
in  the  same  way  and  a  third  portion  of  bacteria-free  sediment  is  separated.  Fre- 
quently a  fourth  serial  centrifugalization  is  performed — always  if  trie  third  sediment 
is  of  appreciable  quantity.  At  all  stages  of  the  separation,  small  portions  of  the 
dilute  hydrochloric  acid  are  used,  so  that  the  final  suspension  shall  not  be  too  vo- 
luminous. Ordinarily  it  amounts  to  125  to  200  c.c.  At  the  same  time,  the  final 
amount  of  fluid  should  not  be  too  small,  as  shown  by  Ehrenpfordt,1  because  the 
viscosity  accompanying  increased  concentration  prevents  proper  and  complete 
sedimentation. 

To  the  final  bacterial  suspension  an  equal  volume  of  alcohol  is  added  and  the 
beaker  set  aside  to  concentrate.  A  water-bath  at  50°  to  6o°C.  is  very  satisfactory. 
After  two  or  three  days,  when  the  liquid  is  concentrated  to  about  50  c.c.,  the  beaker 
is  removed  and  about  200  c.c.  of  alcohol  are  added.  The  beaker  is  covered  and 
allowed  to  stand  at  room  temperature  for  24  hours.  At  the  end  of  this  time  the 
bacterial  substance  is  generally  settled,  so  that  most  of  the  clear  supernatant  liquid, 
of  dark  brown  color,  can  be  directly  siphoned  off  without  loss  of  solid  matter.  The 
remainder  is  then  transferred  to  centrifuge  tubes,  centrifugalized,  and  the  remaining 
clear  liquid  pipetted  off.2  The  sediment  consists  of  the  bodies  of  the  bacteria,  and 
is  transferred  to  a  Kjeldahl  flask  for  nitrogen  determination.  This  is  the  bacterial 
nitrogen.  Where  a  determination  of  bacterial  dry  substance  is  desired,  the  sedi- 
ment of  bacteria  is  extracted  by  absolute  alcohol  and  ether  in  succession,  trans- 
ferred to  a  weighed  porcelain  crucible,  and  dried  at  io2°C.  to  constant  weight. 
This  dried  sample  is  then  used  in  the  nitrogen  determination.  Our  procedure 
differs  from  that  of  MacNeal  in  that  the  bacterial  dry  matter  is  not  determined. 
A  saving  of  about  seven  days'  time  and  of  considerable  labor  is  accomplished  by 
this  omission.  ;  ^ 

Inasmuch  as  it  has  been  shown  by  various  investigators  that  such  bacteria  as 
are  present  in  the  feces  contain  on  the  average  about  n  per  cent  of  nitrogen,  the 
values  for  bacterial  nitrogen  as  determined  by  our  method  may  conveniently  serve 
as  a  basis  for  the  calculation  of  the  actual  output  of  bacterial  substance. 

23.  Quantitative  Determination  of  Indol  in  Feces.  Bergeim's  Modification  of 
the  Herter-Foster  Method.3 — Principle. — The  feces  are  distilled  from  alkaline  solu- 
tion to  remove  phenols.  This  distillate  is  again  distilled  from  acid  solution  to 
remove  ammonia.  The  indol  in  the  final  distillate  is  treated  with  /5-naphthaqui- 
none  sodium  monosulphonate  and  alkali  and  the  blue  compound  formed  extracted 
with  chloroform  and  determined  colorimetrically. 

Procedure. — Rub  30-50  grams  of  the  fresh,  well-mixed  feces  in  a  mortar  with 
water  to  a  uniform  consistency.  Transfer  to  a  wide  mouth  Kjeldahl  flask  of  about 
1000  c.c.  capacity,  rinsing  mortar  and  neck  of  flask  with  distilled  water  to  make 
about  400  c.c.  Add  5  c.c.  of  10  per  cent  KOH  solution  and  about  2  c.c.  of  paraffin 
to  decrease  foaming.  Distill  with  steam  using  ordinary  Kjeldahl  distillation  ap- 

1  Ehrenpfordt:  Zeit.  exp.  Path.  Ther.,  7,  455,  1909. 

2  In  later  work  (see  Blather  wick  and  Hawk:  Biochem.  Bull.,  3,  28,  1913)  it  was  found 
advantageous  to  centrifugalize  with  alcohol  and  ether  in  succession  before  transferring 
the  bacterial  cells  to  Kjeldahl  flasks. 

3Herter  and  Foster:  Jour.  Biol.  Chem.,  i,  257,  1906.  Bergeim:  Jour.  Biol.  Chem. 
32,  17,  1917. 


246  PHYSIOLOGICAL  CHEMISTRY 

paratus  with  good  stream  of  water  in  the  condenser.  Heat  carefully  for  a  few 
minutes  until  danger  of  foaming  is  past  and  then  allow  to  boil  vigorously.  Distill 
over  500  c.c.  of  liquid,  bringing  the  volume  of  the  fecal  suspension  down  to  about 
100  c.c.  toward  the  end  of  the  distillation. 

Transfer  the  distillate  to  a  clean  Kjeldahl  flask,  add  2  drops  of  phenolphthalein 
as  an  indicator.  Make  neutral  with  N  sulphuric  acid  and  add  i  c.c.  excess.  Dis- 
till with  steam  as  before,  collecting  the  first  500  c.c.  of  distillate  and  bringing  the 
residue  finally  to  about  100  c.c.  Mix  distillate  well  by  shaking. 

Take  an  aliquot  portion  of  the  distillate  (100  c.c );  add  i  c.c.  of  a  2  per  cent 
solution  of  /3-naphthaquinone  sodium  monosulphonate  solution.  Then  add  2  c.c. 
of  10  per  cent  KOH.  Shake  and  let  stand  for  1 5  minutes.  This  is  best  carried  out 
in  a  150  c.c.  Squibb  shape  separatory  funnel.  Extract  with  chloroform,  shaking 
vigorously,  using  a  10  c.c.  and  a  7  c.c.  portion  which  will  bring  the  total  volume  of 
the  extract  to  the  mark  of  a  15  c.c.  graduated  tube.  Mix  thoroughly.  Run  at 
the  same  time  and  in  the  same  way  a  standard  using  i  c.c.  of  a  solution  of  indol  o.i 
mg.  of  indol  per  c.c.  Compare  the  extract  with  this  standard  in  a  colorimeter, 
using  the  standard  ordinarily  at  the  30-mm.  mark.  Calculate  the  indol  to  the 
basis  of  milligrams  of  indol  per  gram  of  moist  feces. 

Indol  and  naphthaquinone  solutions  should  be  freshly  prepared  or  may  be 
kept  in  the  ice-box  for  some  days.  Indol  distillates  should  be  kept  in  the  ice-box 
if  not  used  at  once,  especially  in  hot  weather.  The  feces  must  be  fresh. 

24.  Quantitative  Determination  of  Fat  in  Feces. — Principle. — The 
determination  of  fat  in  dried  feces  is  a  more  or  less  tedious  process,  and 
one  which  is  somewhat  dangerous  if  applied  to  pathological  feces.  Most 
of  the  methods  for  the  determination  of  fat  in  the  moist  feces  are  accurate, 
but  require  a  long  time.  Saxon1  has  proposed  a  method  for  the  deter- 
mination of  fat  in  moist  feces,  which  is  speedy,  convenient,  and  accur- 
ate. The  soaps  of  the  feces  are  converted  into  free  fatty  acids  by 
means  of  hydrochloric  acid,  and  the  material  is  then  extracted  by  shak- 
ing with  ether.  The  ether  removes  the  neutral  fat,  the  fatty  acids 
which  were  present  as  such,  the  fatty  acids  derived  from  the  soaps,  and 
the  cholesterol.  The  ether  is  removed  by  distillation,  the  crude  fat 
purified  by  means  of  petroleum  ether,  and  the  weight  of  the  total  fat 
obtained.  The  fat  is  the:nf  dissolved  in  benzene  and  titrated  with  tenth- 
normal  sodium  alcoholate  solution,  using  phenolphthalein  as  an  indi- 
cator. The  fatty  acid  is  calculated,  from  the  titration,  to  stearic  acid. 

Procedure.— Place  about  5  grams  (accurately  weighed)  of  the  thoroughly 
mixed  feces  in  a  100  c.c.  glass-stoppered  graduated  cylinder.2 

Add  20  c.c.  of  distilled  water,  i  to  2.5  c.c.  of  concentrated  hydrochloric  acid 
(depending  upon  the  amount  of  the  sample)  and  again,  sufficient  distilled  water 
to  make  a  total  bulk  of  30  c.c.  Add  exactly  20  c.c.  of  ether,  stopper,  and  shake 

1  Saxon:  /.  Biol.  Chem.,  17,  99,  1914. 

1  Care  must  be  taken  not  to  smear  the  neck  of  the  cylinder.  This  may  be  avoided  by 
removing  the  feces  from  the  weighing  bottle  by  means  of  a  glass  rod,  the  end  of  which  is 
flattened,  and  bent  in  the  shape  of  a  hoe,  and  transferring  small  bits  of  the  feces  from  the  hoe 
to  the  cylinder,  using  short  pieces  of  glass  rod,  which  are  dropped  into  the  cylinder  together 
with  the  feces. 


FECES  247 

vigorously  for  five  minutes.  Allow  to  stand  for  a  few  seconds,  remove  the  stop- 
per, add  exactly  20  c.c.  of  95  per  cent  alcohol,  and  again  shake  for  five  minutes. 

Stand  the  cylinder  aside.  The  ether,  containing  practically  all  of  the  fat,  will 
come  to  the  top  as  a  colored  transparent  layer.  Blow  the  ether  layer  off  into 
a  tall  150-200  c.c.  beaker.1  The  thin  layer  of  ether  which  remains  is  diluted 
with  5  c.c.  of  ether,  the  tube  slightly  agitated,  and  the  ether  blown  off.  This  is 
done  in  all  five  times,  care  being  taken  each  time  to  wash  down  the  sides  of  the 
cylinder.  The  stopper  should  also  be  washed. 

Twenty  c.c.  of  ether  are  again  added,  and  the  cylinder  shaken  for  five  minutes 
and  set  aside.  When  the  ether  has  nearly  stratified,  blow  it  off  and  wash  as 
before.  During  the  second  washing  stratification  will  complete  itself. 

Evaporate  the  ether2  until  no  trace  of  the  alcohol,  which  has  been  carried 
over  with  it,  remains.  To  the  residue  add  30  c.c.  of  low-boiling  petroleum  ether 
(should  boil  below  6o°C.),  and  allow  to  stand  overnight.  Petroleum  ether  for 
this  work  should  be  frequently  tested  for  a  residue  on  evaporation.  If  a  residue 
is  left,  the  ether  should  be  redistilled. 

Filter  the  petroleum  ether  solution  of  the  fat,  catch  the  filtrate  and  washings 
in  a  tall,  weighed,  100  c.c.  beaker,  evaporate  off  the  solvent,  dry  the  beaker  at 
9O°C.,  desiccate  and  weigh. 

After  weighing,  dissolve  the  contents  of  the  beaker  in  50  c.c.  of  benzol,  heat 
almost  to  the  boiling-point,  add  2  drops  of  a  0.5  per  cent  solution  of  phenolph- 
thalein,  and  titrate  with  a  decinormal  solution  of  sodium  alcoholate.8 

Calculations. — The  weight  of  total  fat  is  obtained  by  subtracting  the 
weight  of  the  empty  beaker  from  the  weight  of  the  beaker  plus  the  dried 
fat.  The  weight  of  fatty  acids  (in  terms  of  milligrams  of  stearic  acid) 
is  obtained  by  multiplying  the  number  of  cubic  centimeters  of  deci- 
normal sodium  alcoholate  solution  by  the  factor  28.4.  The  difference 
between  the  weight  of  total  fat  and  the  weight  of  fatty  acids  is  the 
weight  of  neutral  fat  in  the  sample  extracted. 

A  separate  determination  without  the  addition  of  hydrochloric  acid 
may  be  run  upon  the  sample,  for  the  purpose  of  determining  the  weight 
of  neutral  fat  and  free  fatty  acids.  The  difference  between  this  weight 
and  the  weight  of  total  fat  is  the  weight  of  fatty  acid  present  in  the 
original  sample  in  the  form  of  soaps. 

1  This  is  accomplished  in  the  same  manner  that  water  is  blown  from  a  wash  bottle. 
The  submerged  end  of  the  delivery  tube  is  bent  upward,  as  in  the  apparatus  used  for  the 
determination  of  fat  in  milk  by  Meig's  method  (see  Milk).  This  avoids  upward  currents 
which  would  disturb  the  subjacent  alcohol-ether-feces  layer. 

J  Erlenmeyer  flasks  of  about  200  c.c.  capacity  may  be  used,  instead  of  beakers,  for  the 
collection  of  the  ether  blown  from  the  cylinders.  The  ether  may  then  be  distilled  and  re- 
covered. The  same  procedure  may  be  followed  in  removing  the  petroleum  ether. 

J  In  the  preparation  of  the  sodium  alcoholate  solution,  absolute  alcohol  and  freshly  cut, 
bright,  metallic  sodium  are  used;  otherwise  the  procedure  is  the  same  as  that  for  the  stand- 
ardization and  preparation  of  any  alkali  solution. 


CHAPTER  XV 
BLOOD  AND  LYMPH 

BLOOD  is  composed  of  four  types  of  form-elements  (erythrocytes  or 
red  blood  corpuscles,  leucocytes  or  white  blood  corpuscles,  blood  plates 
or  plaques  and  blood  dust  or  hemoconein)  held  in  suspension  in  a  fluid 
called  blood  plasma.     These  form-elements  compose  about  60  per  cent  of 
the  blood,  by  weight.     Ordinarily  blood  is  a  dark  red  opaque  fluid  due  to 
the  presence  of  the  red  blood  corpuscles,  but  through  the  action  of 
certain  substances,  such  as  water,  ether,  or  chloroform,  it  may  be 
rendered  transparent.     Blood  so  altered  was  formerly  said  to  be  laked. 
The  term  hemolysis  is  now  used  in  this  connection  and  substances  which 
cause  such  action  are  spoken  of  as  hemolytic  agents.     The  hemolytic 
process  is  simply  a  liberation  of  the  hemoglobin  from  the  stroma  of 
the  red  blood  corpuscle.     Normal  blood  is  alkaline  in  reaction  to 
litmus,    the  alkalinity   being  due  principally   to   sodium   carbonate. 
When  examined  according  to  physico-chemical  methods  the  blood  is 
found  to  be  very  faintly  alkaline  (PH  =  7-35)-     In  other  words  it 
has  a  hydrogen  ion  concentration  less  than  that  of  water.     Even  in 
cases  of  the  most  pronounced  acidosis  the  reaction  of  the  blood  is 
but  slightly  altered  (see  Chapter  XVII).     The  specific  gravity  of  the 
blood  of  adults  ordinarily  varies  between  1.045  and  i-°75-     It  varies 
somewhat  with  the  sex,  the  blood  of  males  having  a  rather  higher 
specific  gravity  than  that  of  females  of  the  same  species.     Under 
pathological  conditions  also  the  density  of  the  blood  may  be  very  greatly 
altered.     The  freezing-point  (A)  of  normal  blood  is  about  —  o.56°C. 
Variations  between — 0.51°  and  —  o.62°C.  maybe  due  entirely  to  dietary 
conditions,  but  if  any  marked  variation  is  noted  it  can  in  most  cases 
be  traced  to  a  disordered  kidney  function.     The  total  amount  of  blood 
in  the  body  has  been  variously  estimated  at  from  one-twelfth  to  one- 
fourteenth  of  the  body  weight.     Perhaps  1/13.5  is  the  most  satisfactory 
figure.     Abderhalden  and  Schmidt1  have  suggested  a  unique  method 
for  the  determination  of  this  value.     It  is  based  upon  the  change  in 
the  optical  activity  of  the  blood  upon  injection  of  a  body  of  known 
optical  activity,  such,  for  example,  as  dextrin.     Keith,  Rowntree  and 
Geraghty2  have  recently  made  use  of  a  dye  in  the  determination  of 
blood  volume. 

Among  the  most  important  constituents  of  blood  plasma  are  the  four 

Abderhalden  and  Schmidt:  Zeit.  physiol.  chem.,  66,  120,  1910. 
•Keith,  Rowntree  and  Geraghty:  Arch.  Int.  Med.,  16,  509,  1915. 

248 


BLOOD    AND    LYMPH  249 

protein  bodies,  fibrinogen,  nucleoprotein,  serum  globulin  (euglobulin  and 
pseudo-globulin)  and  serum  albumin.  Plasma  contains  about  8.2  per 
cent  of  solids  of  which  the  protein  constituents  named  above  constitute 
approximately  84  per  cent  and  the  inorganic  constituents  (mainly 
chlorides,  phosphates  and  carbonates)  approximately  10  per  cent. 
Among  the  inorganic  constituents  sodium  chloride  predominates.  To 
prevent  coagulation,  blood  plasma  is  ordinarily  studied  in  the  form  of 
an  oxalated  or  salted  plasma.  The  former  may  be  obtained  by  allowing 
the  blood  to  flow  from  an  opened  artery  into  an  equal  volume  of  0.2  per 
cent  ammonium  oxalate  solution,  whereas  in  the  preparation  of  a  salted 
plasma  10  per  cent  sodium  chloride  solution  may  be  used  as  the  diluting 
fluid. 

Fibrinogen  is  perhaps  the  most  important  of  the  protein  constituents 
of  the  plasma.  It  is  also  found  in  lymph  and  chyle  as  well  as  in  certain 
exudates  and  transudates.  Fibrinogen  possesses  the  general  properties 
of  the  globulins,  but  differs  from  serum  globulin  in  being  precipitated 
upon  half-saturation  with  sodium  chloride.  In  the  process  of  coagula- 
tion of  the  blood  the  fibrinogen  is  transformed  into  fibrin.  This  fibrin  is 
one  of  the  principal  constituents  of  the  ordinary  blood  clot.  It  is 
claimed1  that  fibrin  has  the  same  percentage  composition  irrespective 
of  the  source  of  the  blood,  e.g.,  cattle,  sheep,  swine,  etc. 

The  nucleoprotein  of  blood  possesses  many  of  the  characteristics  of 
serum  globulin.  In  common  with  this  body  it  is  easily  soluble  in  sodium 
chloride,  and  is  completely  precipitated  from  its  solutions  upon  satura- 
tion with  magnesium  sulphate.  It  is  much  less  soluble  in  dilute  acetic 
acid  than  serum  globulin,  and  its  solutions  coagulate  at  65°-69°C. 

The  body  formerly  called  serum  globulin  is  probably  not  an  indi- 
vidual substance.  Recent  investigations  seem  to  indicate  that  it 
may  be  resolved  into  two  individual  bodies  called  euglobulin  and  pseudo- 
globulin.  The  euglobulin  is  practically  insoluble  in  water  and  may  be 
precipitated  in  the  presence  of  28-36  per  cent  of  saturated  ammonium 
sulphate  solution.  The  pseudo-globulin,  on  the  contrary,  is  soluble  in 
water  and  is  only  precipitated  by  ammonium  sulphate  in  the  presence  of 
from  36  to  44  per  cent  of  saturated  ammonium  sulphate  solution. 

In  common  with  serum  globulin  the  body  known  as  serum  albumin 
seems  also  to  consist  of  more  than  a  single  individual  substance.  The 
so-called  serum  albumin  may  be  separated  into  at  least  two  distinct 
bodies,  one  capable  of  crystallization,  the  other  an  amorphous  body. 
The  solution  of  either  of  these  bodies  in  water  gives  the  ordinary  albu- 
min reactions.  The  coagulation  temperature  of  the  serum  albumin  mix- 
ture as  it  occurs  in  serum  or  plasma  varies  from  70°  to  85°C.  according  to 

1  Gortner  and  Wuertz:  Jour.  Am.  Chem.  Soc.t  39,  2239,  1917. 


250  PHYSIOLOGICAL  CHEMISTRY 

the  reaction  of  the  solution  and  its  content  of  inorganic  material. 
Serum  albumin  differs  from  egg  albumin  in  being  more  levorotatory, 
in  being  rendered  less  insoluble  by  alcohol,  and  in  the  fact  that  when 
precipitated  by  hydrochloric  acid  it  is  more  easily  soluble  in  an  excess  of 
the  reagent. 

When  blood  coagulates  and  the  usual  clot  forms,  a  light  yellow  fluid 
exudes.  This  is  blood  serum.  It  differs  from  blood  plasma  in  contain- 
ing a  large  amount  of  fibrin  ferment,  a  body  of  great  importance  in  the 
coagulation  of  the  blood,  and  also  in  possessing  a  lower  protein  content. 
The  protein  material  present  in  plasma  and  not  found  in  serum  is  the 
fibrinogen  which  is  transformed  into  fibrin  in  the  process  of  coagulation 
and  removed.  The  specific  gravity  of  the  serum  of  human  blood 
varies  between  1.026  and  1.032.  If  blood  be  drawn  into  a  vessel  and 
allowed  to  remain  without  stirring  or  agitation  of  any  sort  the  major 
portion  of  the  red  corpuscles  will  sink  away  from  the  upper  surface, 
causing  this  portion  of  the  clot  to  assume  a  lighter  color  due  to  the 
predominance  of  leucocytes.  This  light-colored  portion  of  the  clot  is 
called  the  "buffy  coat." 

Beside  the  protein  constituents  already  mentioned,  other  bodies 
which  are  found  in  both  the  plasma  and  serum  are  the  following:  Sugar 
(glucose),  uric  acid  (urates),  urea,  fat,  amino-acids,  enzymes,  lecithin, 
creatine,  carbamic  acid,  cholesterol  and  its  esters,  nucleo protein,  acetone 
bodies,  paralactic  acid,  gases,  ammonia,  coloring-matter  (lutein  or  ipo- 
chrome)  and  mineral  substances.  In  addition  to  the  substances  just 
named  the  blood  doubtless  contains  a  class  of  substances  called  hor- 
mones of  which  adrenaline  is  the  only  one  thus  far  definitely  identified. 
Some  of  the  pathological  constituents  of  blood  are  proteoses,  biliary  con- 
stituents and  purine  bodies.  In  many  pathological  conditions  certain 
normal  constituents  are  present  in  increased  amount. 

Normal  human  blood  contains  slightly  less  than  o.i  per  cent  of 
glucose  on  the  average.  Strouse,1  in  a  very  recent  series  of  tests,  places 
the  average  glucose  content  at  0.084  per  cent.  That  the  diet  influences 
the  sugar  content  is  shown  by  the  fact  that  two  and  one-half  to  four 
hours  after  a  meal  the  sugar  content  has  been  found  to  equal  0.18  per 
cent.2  In  case  of  glycosuria  the  blood  sugar  may  increase  (hypergly- 
cemia)  to  "0.3-1,0  per  cent.  For  the  quantitative  determination  of 
blood  sugar  see  page  283. 

The  determination  of  the  cholesterol  content  of  the  blood  is  assuming 
clinical  importance.  Normal  blood  contains  140-180  mg.  per  100 
grams  of  blood,  or  about  0.15  per  cent.  This  value  has  been  found  to 
be  increased  (hypercholesterolemia)  in  gall  stones,  pregnancy,  nephritis, 

Strouse:  Bitll.  Johns  Hop.  Hosp.,  26,  211,  1915. 
•Hirsch:  Zeil.  physiok  Chem.,  93,  355,  1915. 


BLOOD  AND   LYMPH  251 

diabetes,  arteriosclerosis,  and  syphilis.  (See  page  291  for  quantitative 
method.) 

Uric  acid  is  present  in  normal  blood  to  the  extent  of  about  2-3  mg. 
per  100  c.c.  of  blood.  In  gout  this  value  may  be  increased  to  4-10  mg. 
The  quantitative  determination  of  the  uric  acid  content  of  blood  is  of 
importance  as  an  aid  in  differentiating  gout  and  certain  other  disorders 
exhibiting  similar  clinical  symptoms  (for  methods  see  page  281). 

The  non-protein  nitrogen  of  normal  blood  amounts  to  about  25-30 
mg.  per  100  c.c.  of  blood.  The  urea  forms  about  50  per  cent  of  this, 
creatinine  2  per  cent,  uric  acid  2  per  cent,  ammonia  0.3  per  cent,  and 
amino-acids,  etc.,  about  46  per  cent.  In  nephritis  the  non-protein 
nitrogen  of  the  blood  is  much  increased.  In  the  laboratories  of  Jeffer- 
son Medical  College  analysis  of  the  blood  in  a  fatal  case  of  uremia 
»  showed  a  non-protein  nitrogen  value  above  46*0  mg. l 

Amino-acids  are  always  present  in  the  blood.  They  result  for  the 
most  part  from  the  digestion  of  protein  material  in  the  intestine. 

Creatinine  occurs  in  normal  blood  to  the  extent  of  about  1-2  mg. 
per  100  c.c.  of  blood.  In  uremia  the  amount  is  increased.8  Various 
investigators  report  the  values  as  ranging  from  4  to  35  mg.  per  100  c.c. 

The  creatine  content  of  normal  blood  averages  about  3  mg.  per 
100  c.c.  of  blood.  The  creatine  values  have  no  important  pathological 
significance  as  far  as  known  at  the  present  time. 

The  acetone  (acetone  and  acetoacetic  acid)  content  of  normal  blood 
ranges  from  o  to  i  mg.  per  100  c.c.  of  blood.  In  mild  diabetes  mellitus 
the  value  rises  to  5-12  mg.,  whereas  in  severe  diabetes  mellitus  (coma) 
as  much  as  20-45  m£-  Per  IO°  c-c-  °f  blood  serum  has  been  found. 

Normal  blood  contains  about  20  per  cent  of  solids  and  3  per  cent  of 
total  nitrogen,  whereas  chlorides  are  present  to  the  extent  of  about  0.50 
per  cent.  In  severe  diabetes  the  chlorides  are  decreased  because  of  the 
accompanying  diuresis. 

Abel3  and  associates  have  devised  a  method  by  which  diffusible 
substances  may  be  removed  from  the  blood  of  a  living  animal.  The 
process  is  termed  vividiffusion  and  is  brought  about  by  permitting  the 
blood  from  an  artery  to  flow  through  collodion  tubes  surrounded  by 
physiological  salt  solution.  The  dialyzable  substances,  except  sodium 
chloride,  are  removed  and  the  dialyzed  blood  is  returned  to  the  body  of 
the  animal  by  means  of  a  vein.  The  apparatus  has  been  modified  by 
McGuigan  and  von  Hess.4 

1  Weiss  and  Hamilton:  Reported  before  College  of  Physicians,  Philadelphia  May,  1921, 
unpublished. 

JFolin  and  Denis:    Jour.  Biol.  Chem.,  17,  487,  1914. 
Myers  and  Fine:  Jour.  Biol.  Chem.,  20,  391,  1915. 

3  Abel,  Rowntree  and  Turner:  Transactions  of  the  Ass'n  of  American  Physicians,  1913; 
also  Jour,  of  P harm,  and  Exp.  Therap.,  5,  275,  1914. 

4 McGuigan  and  Von  Hess:  Jour.  Pharm.  and  Exp.  Therap.,  vol.  6,  1914, 


252  PHYSIOLOGICAL  CHEMISTRY 

In  the  application  of  blood-letting  or  venesection  it  has  been  cus- 
tomary to  discard  both  the  corpuscles  and  plasma  of  the  withdrawn 
blood.  Abel1  and  associates  have  found  it  possible  to  separate  the 
corpuscles  from  the  removed  blood  by  centrifugation  and  to  return 
them  to  the  body  suspended  in  Locke's  solution.  They  name  the  pro- 
cedure plasmaphceresis.  By  this  means  blood-letting  can  be  carried 
out  repeatedly  during  a  short  interval  of  time  without  endangering  the 
life  of  the  animal. 

There  has  been  considerable  controversy  regarding  the  form  of  the 
erythrocytes  or  red  blood  corpuscles  of  human  blood.  It  is  claimed  by 
some  investigators  that  the  cells  are  bell-shaped  or  cup-shaped.  As  the 
erythrocytes  occur  normally  in  the  circulation,  however,  they  are  prob- 
ably thin,  non-nucleated,  biconcave  discs.2 

The  blood  of  most  mammals  contains  erythrocytes  similar  in  form 
to  those  of  human  blood.  In  the  blood  of  birds,  fishes,  amphibians  and 
reptiles  the  erythrocytes  are  ordinarily  more  or  less  elliptical,  biconvex 
and  possess  a  nucleus.  The  erythrocytes  vary  in  size  with  the  different 
animals.  The  average  diameter  of  the  erythrocytes  of  blood  from 
various  species  is  given  in  the  following  table  :  3 


Elephant  ...........................................  sVW  of  an  i 

Guinea-pig  .........................................  j^sj  of  an  inch. 

Man  ...  .................................  ...........  nfar  °*  an  !nc^' 

Monkey  .............................................  ^sV2  of  an  inch. 

Dog  ............  ....................................  3^6  T  of  an  inch. 

Rat  .....................................  ............  yiVs  of  an  inch. 

Rabbit  ..............  .  ...............................  T^S  of  an  inch. 

Mouse  ..............................................  FfV?  of  an  inch. 

Lion  ...............  .....................  .  ...........  ijifs  of  an  inch. 

Ox  ...........................  ...  ....................  f^ry  of  an  inch. 

Horse  .....................  ...  .......................  4^  of  an  inch. 

Pig  .................................................  f-^Q  of  an  inch. 

Cat  .................................................  -ffrs  of  an  inch. 

Sheep  ............................  ...................  -$fos  of  an  inch. 

Goat  .......................................  .........  i-Jrj  of  an  inch. 

Musk-deer  ...........................................  rsfe  of  an  inch. 


The  erythrocytes,  from  whatever  source  obtained,  consist  essentially 
of  two  parts,  the  stroma  or  protoplasmic  tissue  and  its  enclosed  pigment, 
hemoglobin.  For  human  blood  the  number  of  erythrocytes  present  in 
the  fluid  as  obtained  from  well-developed  males  in  good  physical  condi- 
tion is  about  5,500,000  per  cubic  millimeter.4  The  normal  content  of 
the  blood  "of  adult  females  is  from  4,000,000  to  4,500,000  per  cubic 

1Abel,  Rowntree,  Turner,  Marshall  and  Lamson  (see  Abel's  Mellon  Lecture,"  1915): 
also  Abel:  Science,  42,  135,  1915. 

2  When  examined  singly  under  the  microscope,  they  possess  a  pale  greenish-yellow 
color  (see  Plate  IV,  opposite),  whereas  when  grouped  in  large  masses  a  reddish  tint  is 
noted. 

3  Wormley's  Micro-Chemistry  of  Poisons,  second  edition,  p.  733. 

*  This  statement  is  based  upon  observations  made  upon  the  blood  of  athletes  in  training. 
See  Hawk:  Amer.  Jour.  Physiol.,  10,  384,  1904.  It  is  generally  stated  in  text-books  that 
the  blood  of  males  contains  about  5,000,000  per  cubic  millimeter. 


PLATE  IV. 


NORMAL  ERYTHROCYTES  AND  LEUCOCYTES. 


BLOOD    AND    LYMPH  253 

millimeter.  The  number  of  erythrocytes  varies  greatly  under  different 
conditions.  For  instance,  the  number  may  be  increased  after  the  trans- 
fusion of  blood  of  the  same  species  of  animals;  by  residing  in  a  high 
altitude;  or  as  a  result  of  strenuous  physical  exercise  continued  over  a 
short  period  of  time.  An  increase  is  also  noted  in  starvation;  after 
partaking  of  food;  after  cold  or  hot  baths;  after  massage,  in  partial 
asphyxia,  and  after  fright,  as  well  as  after  the  administration  of  certain 
drugs  and  accompanying  certain  diseases,  such  as  cholera,  diarrhea, 
dysentery  and  yellow  atrophy  of  the  liver.  A  decrease  in  the  number 
occurs  in  the  different  forms  of  anemia.  The  number  has  been 
known  to  increase  to  7,040,000  per  cubic  millimeter  as  a  result  of 
physical  exercise,  while  11,000,000  per  cubic  millimeter  have  been 
noted  in  cases  of  polycythemia  and  increases  nearly  as  great  in  cyanosis. 
The  number  has  been  known  to  decrease  to  500,000  per  cubic  milli- 
meter or  lower  in  pernicious  anemia. 

Erythrocytes  possess  the  property,  when  properly  treated,  of 
" clumping"  together  in  masses  and  precipitating,  producing  so-called 
agglutination.  Cells  other  than  erythrocytes  (e.g.,  bacteria)  possess 
this  property.  When  spoken  of  in  connection  with  the  blood  such 
action  is  termed  hemagglutination.  A  substance  which  will  bring  about 
hemagglutination  is  said  to  contain  hemagglutinins.  These  hem- 
agglutinins  are  particularly  abundant  in  the  vegetable  kingdom.1  For 
a  demonstration  of  hemagglutination  see  page  265. 

Oxyhemoglobin,  the  coloring  matter  of  the  blood,  is  a  conjugated 
protein.  Through  treatment  with  hydrochloric  acid  it  may  be  split  into 
a  protein  body  called  globin,  and  hemochromogen,  an  iron-containing 
pigment.  The  latter  body  is  rapidly  transformed  into  hematin  in  the 
presence  of  oxygen,  and  this  in  turn  gives  place  to  hematin-hydrochlor- 
ide  or  hemin  (Figs.  84  and  85,  page  268).  The  pigment  of  arterial  blood 
is  for  the  most  part  loosely  combined  with  oxygen  and  is  termed  oxy- 
hemoglobin,  whereas  the  pigment  of  venous  blood  is  principally  hemo- 
globin (so-called  reduced  hemoglobin).  Oxyhemoglobin  is  the  oxygen 
carrier  of  the  body  and  belongs  to  the  class  of  bodies  known  as  respira- 
tory pigments.  It  is  held  within  the  stroma  of  the  erythrocyte.  The  re- 
duction of  Oxyhemoglobin  to  form  hemoglobin  (so-called  reduced  hemo- 
globin) occurs  in  the  capillaries.  Oxyhemoglobin  may  be  crystallized 
and  a  specific  form  of  crystal  obtained  from  the  blood  of  each  individual 
species  (see  Figs.  76  to  82,  pages  254  to  257).  This  fact  seems  to  indi- 
cate that  there  are  many  varieties  of  Oxyhemoglobin.  The  interesting 
findings  of  Reichert  and  Brown  are  of  great  value  in  this  connection. 
These  investigators  prepared  Oxyhemoglobin  crystals  from  the  blood 

1  Mendel:  Archivio  di  fisiologia,  7,   168,   1909;  also  Schneider:  Journal  of  Biological 
Chem.,  n,  47,  1912. 


254 


PHYSIOLOGICAL   CHEMISTRY 


5fcl          .  ^r\A»-  -+i 

«B*  4       *        ^f^     " 

V5S5*1 


FlG,    76. — OXYHEMOGLOBIN  CRYSTALS  FROM^BLOOD  OF  THE  GUINEA-PIG. 

Reproduced  from  a  micro-photograph  furnished  by  Prof.  E.  T.  Reichert,  of  the  University 

of  Pennsylvania. 


FIG.  77. — OXYHEMOGLOBIN  CRYSTALS  FROM  BLOOD  OF  THE  RAT. 

Reproduced  from  a  micro-photograph  furnished  by  Prof.  E.  T.  Reichert,  of  the  University 

of  Pennsylvania. 


BLOOD  AND   LYMPH 


255 


FlG.   78. — OXYHEMOGLOBIN  CRYSTALS  FROM  BLOOD  OF  THE  HORSE. 

Reproduced  from  a  micro-photograph  furnished  by  Prof.  E.  T.  Reichert,  of  the  University 

of  Pennsylvania. 


m 


FIG.  79.— OXYHEMOGLOBIN  CRYSTALS  FROM  BLOOD  OF  THE  SQUIRREL. 
Reproduced  from  a  micro-photograph  furnished  by  Prof.  E.  T.  Reichert,  of  the  University 

of  Pennsylvania. 


256 


PHYSIOLOGICAL   CHEMISTBY 


FlG.    80. — OXYHEMOGLOBIN  CRYSTALS  FROM  BLOOD  OF  THE  DOG. 

Reproduced  from  a  micro-photograph  furnished  by  Prof.  E.  T.  Reichert,  of  the  University 

of  Pennsylvania. 


FIG.  81. — OXYHEMOGLOBIN  CRYSTALS  FROM  BLOOD  OF  THE  CAT. 

Reproduced  from  a  micro-photograph  furnished  by  Prof.  E.  T.  Reichert,  of  the  University 

of  Pennsylvania. 


BLOOD   AND    LYMPH 


257 


of  over  one  hundred  species  of  animal  and  subsequently  studied  the 
characteristics  of  the  crystals  very  minutely  from  the  standpoint  of 
crystallography.  Their  findings  may  prove  of  importance  from  the 
standpoint  of  heredity  and  the  origin  of  species. 


FlG.   82. — OXYHEMOGLOBIN  CRYSTALS  FROM  BLOOD  OF  THE  NECTURUS. 

Reproduced  from  a  micro-photograph  furnished  by  Prof.  E.  T.  Reichert,  of  the  University 

of  Pennsylvania.1 


Carbon  monoxide  hemoglobin 


HEMOGLOBIN 


Acid  hematin  (+  globin) 


Hemin 

(Hematin  hydrochloride) 


Hemochromogen 
Methemoglobin 


Alkaline  hematin  (+  globin) 


Hemin 

(Hematin  hydrochloride) 


Acid  hematoporphyrin  (+  iron) 


Alkaline  hematoporphyrin 

1  The  micro-photographs  of  oxyhemoglobin  (see  pages  254-257)  and  hemin^(see  page 
268)  are  reproduced  through  the  courtesy  of  Professors  E.  T.  Reichert  and  Amos  P.  Brown, 
of  the  University  of  Pennsylvania,  who  have  investigated  the  crystalline  forms  of  bio- 
chemic  substances. 


258  PHYSIOLOGICAL  CHEMISTRY 

The  following  bodies  may  be  derived  from  hemoglobin,  and  each 
possesses  a  specific  absorption  spectrum  which  serves  as  an  aid  in 
its  detection  and  identification:  Oxyhemoglobin,  methemoglobin, 
carbon-monoxide  hemoglobin,  nitric-oxide  hemoglobin,  hemochromo- 
gen,  hematin,  acid-hematin,  alkali-hematin  and  hematoporphyrin 
(see  Absorption  Spectra,  Plates  I  and  II). 

The  relationship  between  hemoglobin  and  its  derivatives  may  be 
represented  by  the  scheme  shown  on  page  257. 

The  chemical  transformations  which  occur  in  the  blood  during  respira- 
tion are  complicated  and  of  great  importance.  In  brief  the  exchange  of 
oxygen  and  carbon  dioxide  may  be  described  as  follows :  Oxygen  from 
the  air  passes  through  the  lungs  into  the  blood  where  it  is  appropriated 
for  the  most  part  by  the  red  blood  corpuscles.  The  hemoglobin  of 
these  corpuscles  possesses  the  property  of  uniting  with  oxygen,  forming 
oxyhemoglobin.  This  oxyhemoglobin  possesses  a  red  color  and  imparts 
to  the  arterial  blood  its  bright  appearance.  The  oxygen  is  thus  borne 
by  these  blood  cells  in  the  circulating  blood  to  all  parts  of  the  body. 
As  the  blood  passes  through  the  capillaries  it  gives  up  the  major  part  of 
its  oxygen  which  is  used  by  the  tissues  in  their  varied  activities.  As  the 
blood  loses  its  oxygen  it  becomes  darker  in  color  due  to  the  fact  that 
the  oxyhemoglobin  has  been  transformed  into  hemoglobin  (or  reduced 
hemoglobin) .  At  the  same  time  in  the  tissue  capillaries  the  blood  takes 
up  excretory  products  from  the  tissues,  the  chief  of  which  is  carbon 
dioxide.  This  carbon  dioxide  is  present  in  the  blood  mainly  as  carbonic 
acid  and  sodium  acid  carbonate ;  a  small  amount  is  probably  combined 
with  the  proteins  of  the  plasma.  We  now  have  so-called  venous  blood. 
This  is,  in  turn,  carried  to  the  lungs  where  the  carbon  dioxide  is 
exchanged  for  oxygen  and  the  cycle  is  repeated. 

The  white  corpuscles  (or  leucocytes)  of  human  blood  differ  from 
the  red  corpuscles  (or  erythrocytes)  in  many  particulars,  such  as  being 
somewhat  larger  in  size,  in  containing  at  least  a  single  nucleus  and  in 
possessing  ameboid  movement  (see  Plate  IV,  opposite  page  252). 
They  are  typical  animal  cells  and  therefore  contain  the  following  bodies 
which  are  customarily  present  in  such  cells:  Proteins,  fats,  glycogen, 
purine  bodies,  enzymes,  phosphatides,  lecithin,  cholesterol,  inorganic  salts, 
and  water.  Compound  proteins  make  up  the  chief  part  of  the  protein 
quota  of  leucocytes,  the  nucleoproteins  predominating.  Of  the  en- 
zymes present  the  proteolytic  are  the  most  important.  It  is  claimed1 
that  there  are  two  proteolytic  enzymes  in  leucocytes,  one  active  in 
alkaline  solution  and  present  in  the  polynuclear  cells,2  and  the  other 

^pie:  Jour,  of  Experimental  Med.y  8;  Opie  and  Barker:  Ibid.,  9. 
2 For  discussion  of  different  types  of  leucocytes  see  "Da  Costa's  Clinical  Hematology" 
or  some  similar  volume. 


BLOOD    AND    LYMPH  259 

active  in  acid  medium  and  present  in  mononuclear  cells.  It  is  claimed 
that  the  granular  leucocytes  originate  in  the  bone  marrow,  whereas 
the  non-granular  leucocytes  (lymphocytes)  have  a  lymphatic  origin 
(lymph  glands  or  lymphoid  tissue) ;  this  matter  of  origin  is  uncertain. 
The  normal  number  of  leucocytes  in  human  blood  varies  between  5000 
and  10,000  per  cubic  millimeter.  The  ratio  between  the  leucocytes  and 
erythrocytes  is  about  i  1350-500.  A  leucocytosis  is  said  to  exist  when 
the  number  of  leucocytes  is  increased  for  any  reason.  Leucocytoses 
may  be  divided  into  two  general  classes,  the  physiological  and  the 
pathological.  Under  the  physiological  form  would  be  classed  those 
leucocytoses  accompanying  pregnancy,  parturition  and  digestion,  as  well 
as  those  due  to  mechanical  and  thermal  influences.  The  leucocytoses 
spoken  of  as  pathological  are  the  inflammatory  ^infectious,  post-hemor- 
rhagic,  toxic  and  experimental  forms,  as  well  as  the  type  of  leucocytosis 
which  accompanies  malignant  disease. 

The  blood  plates  (platelets  or  plaques)  are  round  or  oval  colorless 
discs  which  possess  a  diameter  about  one-third  as  great  as  that  of  the 
erythrocytes.  Upon  treatment  with  certain  reagents,  e.g.,  artificial 
gastric  juice,  they  may  be  separated  into  a  homogeneous,  non-refractive 
portion  and  a  granular,  refractive  portion.  The  blood  plates  are 
associated  with  the  coagulation  of  the  blood.  This  relationship  is  not 
completely  understood  at  present. 

The  hemoconein  or  so-called  "blood  dust"  is  made  up  of  round 
granules  which  usually  have  a  diameter  somewhat  less  than  i  micron. 
The  serum  of  normal  as  well  as  of  pathological  blood  contains  these 
granules.  They  were  first  described  by  Miiller  to  whom  they  appeared 
as  highly  refractile  granules  possessed  of  Brownian  movement.  The 
"blood  dust"  is  apparently  not  concerned  with  the  coagulation  of  the 
blood.  The  granules  are  insoluble  in  alcohol,  ether  and  acetic  acid 
and  are  not  blackened  by  osmic  acid.  According  to  Miiller,  the  gran- 
ules making  up  the  so-called  "blood  dust"  constitute  a  new  organized 
constituent  of  the  blood,  whereas  other  investigators  believe  them  to  be 
merely  free  granules  from  certain  of  the  forms  of  leucocytes.  They 
appear  to  possess  no  clinical  significance. 

The  processes  involved  in  the  coagulation  of  the  blood  are  not  fully 
understood.  Several  theories  have  been  advanced  and  each  has  its 
adherents.  The  theory  which  appears  to  be  fully  as  firmly  founded 
upon  experimental  evidence  as  any  is  the  following:  Blood  contains  a 
zymogen  called  prothrombin  which  combines  with  the  calcium  salts 
present  to  form  an  enzyme  known  as  thrombin  or  fibrin-ferment.  When 
blood  is  drawn  from  a  vessel  the  fibrin-ferment  at  once  acts 
upon  the  fibrinogen  present  and  gives  rise  to  the  formation  of  fibrin. 


260  PHYSIOLOGICAL  CHEMISTRY 

This  fibrin  forms  in  shreds  throughout  the  blood  mass  and,  hold- 
ing the  form  elements  of  the  blood  within  its  meshes,  serves  to  pro- 
duce the  typical  blood  clot.  The  fibrin  shreds  gradually  contract,  the 
clot  assumes  a  jelly-like  appearance  and  the  yellowish  serum  ex- 
udes. If,  immediately  upon  the  withdrawal  of  blood  from  the  body, 
the  fluid  be  rapidly  stirred  or  thoroughly  "  whipped"  with  a  bundle  of 
coarse  strings,  twigs  or  a  specially  constructed  beater,  the  fibrin  shreds 
will  not  form  in  a  network  throughout  the  blood  mass  but  instead  will 
cling  to  the  device  used  in  beating.  In  this  way  the  fibrin  may  be 
removed  and  the  remaining  fluid  is  termed  defibrinated  blood.  The 
above  theory  of  the  coagulation  of  the  blood  may  be  stated  briefly  as 
follows: 

I.  Prothrombin  +  Calcium  Salts  =  Thrombin  (or  Fibrin-ferment) . 

II.  Thrombin  (or  Fibrin-ferment)  +  Fibrinogen  =  Fibrin. 
Howell1  has  suggested  an  ingenious  modification  of  the  above  theory. 

He  says:  "In  the  circulating  blood  we  find  as  constant  constituents 
fibrinogen,  prothrombin,  calcium  salts  and  antithrombin.  The  last-named 
substance  holds  the  prothrombin  in  combination  and  thus  prevents  its 
conversion  or  activation  to  thrombin.  When  the  blood  is  shed,  the 
disintegration  of  the  corpuscles  (platelets)  furnishes  material  (throm- 
boplastin)  which  combines  with  the  antithrombin  and  liberates  the 
prothrombin;  the  latter  is  then  activated  by  the  calcium  and  acts  on 
the  fibrinogen.  According  to  this  view  the  actual  process  of  coagula- 
tion involves  only  three  factors,  fibrinogen,  prothrombin  and  calcium. 
These  three  factors  exist  normally  in  the  circulating  blood  but  are 
prevented  from  reacting  by  the  presence  of  antithrombin." 

The  question  as  to  whether  menstrual  blood  coagulates  has  caused 
much  discussion.  The  most  recent  investigations  seem  to  show  that  it 
does  not  coagulate  because  of  the  removal  of  fibrin-ferment  and  fibrinogen 
from  such  blood  by  the  endometrium  or  lining  membrane  of  the  uterus.2 

Among  the  medico-legal  tests  for  blood  are  the  following:  (i) 
Microscopical  identification  of  the  erythrocytes,  (2)  spectroscopic  iden- 
tification of  blood  solutions,  (3)  the  guaiac  test,  (4)  the  benzidine 
reaction,  (5)  preparation  of  hemin  crystals,  (6)  Bordet  reaction 
("biological"  blood  test).  This  last  test  is  the  most  satisfactory 
medico-legal  test  for  blood. 

Up  to  within  recent  times  it  has  been  impossible  to  make  an  absolute 
differentiation  of  human  blood.  The  so-called  "biological"  blood  test 
has,  however,  made  such  a  differentiation  possible.  This  test,  known  as 
the  Bordet  reaction,  is  founded  upon  the  fact  that  the  blood  serum  of  an 

1  Howell:  American  Journal  of  Physiology ;  29,  187,  1911.  " 

*Bell:  Jour.  Path,  and  Bad.,  18,  No.  4,  1914. 


BLOOD   AND    LYMPH  261 

animal  into  which  has  been  injected  the  blood  of  another  animal  of 
different  species  develops  the  property  of  agglutinating  and  dissolving 
erythrocytes  similar  to  those  injected,  but  exerts  this  influence  upon 
the  blood  from  no  other  species.  The  atitiserum  used  in  this  test  is 
prepared  by  injecting  rabbits  with  5-10  c.c.  of  human  defibrinated 
blood,  at  intervals  of  about  four  days,  until  a  total  of  between  50  and  80 
c.c.  has  been  injected.  After  a  lapse  of  one  or  two  weeks  the  animal  is 
bled,  the  serum  collected,  placed  in  sterile  tubes  and  preserved  for  use  as 
needed.  In  examining  any  specific  solution  for  human  blood  it  is  simply 
necessary  to  combine  the  antiserum  and  the  solution  under  examina- 
tion in  the  proportion  of  1:100  and  place  the  mixture  at  37°C. 
If  human  blood  is  present  in  the  solution  a  turbidity  will  be  noted 
and  this  will  change  within  three  hours  to  a  distinctly  flocculent 
precipitate.  This  antiserum  will  react  thus*  with  no  other  known 
substance. 

Of  the  other  five  blood  tests  mentioned  the  last  two  named  are 
generally  considered  to  be  the  most  satisfactory.  They  give  equally 
reliable  results  with  fresh  blood  and  with  blood  from  clots  or  stains 
of  long  standing,  provided  the  latter  have  not  been  exposed  to  a  high 
temperature  or  to  the  rays  of  the  sun  for  a  long  period.  The  technic 
of  the  tests  is  simple  and  the  formation  of  the  dark  brown  or  chocolate- 
colored  crystals  of  hemin  or  the  production  of  the  green  or 
blue  color  with  benzidine  is  indisputable  proof  of  the  presence  of  blood 
in  the  fluid,  clot  or  stain  examined.  The  weak  point  of  the  tests, 
medico-legally,  lies  in  the  fact  that  they  do  not  differentiate  between 
human  blood  and  that  of  certain  other  species  of  animal. 

The  guaiac  test  (see  page  265),  although  generally  considered  less 
accurate  than  the  hemin  test,  is  held  by  some  to  be  a  more  delicate  test 
than  the  hemin  test,  if  properly  performed.  One  of  the  most  common 
mistakes  in  the  manipulation  of  this  test  is  the  use  of  a  guaiac  solution 
which  is  too  concentrated  and  which,  when  brought  into  contact  with 
the  aqueous  blood  solution,  causes  the  separation  of  a  voluminous 
precipitate  of  a  resinous  material  which  may  obscure  the  blue  colora- 
tion; this  is  particulary  true  of  the  test  when  used  for  the  examination 
of  blood  stains.  A  solution  of  guaiac  made  by  dissolving  i  gram  of  the 
resin  in  60  c.c.  of  95  per  cent  alcohol  is  very  satisfactory  for  general  use. 
The  test  is  frequently  objected  to  upon  the  ground  that  various  other 
substances,  e.g.,  milk,  pus,  saliva,  etc.,  respond  to  the  test  and  that  it 
cannot  therefore  be  considered  a  specific  test  for  blood  and  is  of  value 
only  in  a  negative  sense.  We  have  demonstrated  to  our  own  satisfac- 
tion, however,  that  many  samples  of  milk  give  the  blue  color  upon  the 
addition  of  an  alcoholic  solution  of  guaiac  resin  without  the  addition  of 


262  PHYSIOLOGICAL  CHEMISTRY 

hydrogen  peroxide  or  old  turpentine.  It  has  also  been  shown1  that 
those  milks  which  respond  positively,  fail  to  do  so  after  boiling.  In  the 
case  of  blood  the  test  is  positive  both  before  and  after  boiling  the  blood 
for  15-20  seconds.  Pus  does  not  respond  after  boiling.  Old,  partly 
putrified  pus  gives  the  test  even  without  the  addition  of  hydrogen 
peroxide  or  old  turpentine,  whereas  fresh  pus  responds  upon  the  addi- 
tion of  hydrogen  peroxide.  Saliva  gives  a  positive  reaction  only  in 
case  blood  or  pus  is  present.  Certain  plant  extracts  give  the  test  before 
but  not  after  boiling  for  15-20  seconds.  Buckmaster  has  advocated 
the  use  of  an  alcoholic  solution  of  guaiaconic  acid  instead  of  an  alcoholic 
solution  of  guaiac  resin.  He  claims  that  he  was  able  to  produce  the 
blue  color  upon  the  addition  of  the  guaiaconic  acid  to  milk  only  when 
the  sample  of  milk  tested  was  brought  from  the  country  in  sterile  bottles, 
and  further,  that  no  sample  of  London  milk  which  he  examined  responded 
to  the  test.  In  the  application  of  the  guaiac  test  to  the  detection  of 
blood,  he  states  that  he  was  able  to  detect  laked  blood  when  present  in 
the  ratio  1:5,000,000  and  unlaked  blood  when  present  in  the  ratio 
1:1,000,000.  This  author  considers  the  guaiac  test  to  be  far  more 
trustworthy  than  is  generally  believed. 

Lymph  may  be  considered  as  the  "middle  man"  in  the  transactions 
between  blood  and  tissues.  It  is  the  medium  by  which  the  nutritive 
material  and  oxygen  transported  by  the  blood  for  the  tissues  is  brought 
into  intimate  contact  with  those  tissues  and  thus  utilized.  In  the 
further  fulfillment  of  its  function,  the  lymph  bears  from  the  tissues 
water,  salts  and  the  products  of  the  activity  and  catabolism  of  the 
tissues  and  passes  these  into  the  blood.  Lymph,  therefore,  exercises 
the  function  of  a  "go-between"  for  blood  and  tissues.^  It  bathes  every 
active  tissue  of  the  animal  body,  and  is  believed  to  have  its  origin  partly 
in  the  blood  and  partly  in  the  tissues. 

In  chemical  characteristics,  lymph  resembles  blood  plasma.  In  fact, 
it  has  been  termed  "blood  without  its  red  corpuscles."  Lymph  from 
the  thoracic  duct  of  a  fasting  animal  or  from  a  large  lymphatic  vessel  of 
a  well-nourished  animal  is  of  a  variable  color  (colorless,  yellowish  or 
slightly  reddish)  and  alkaline  in  reaction  to  litmus.  It  contains 
fibrinogen,  fibrin-ferment  and  leucocytes  and  coagulates  slowly,  the  clot 
being  less  firm  and  bulky  than  the  blood  clot.  Serum  albumin  and 
serum  globulin  are  both  present  in  lymph,  the  albumin  predominating 
in  a  ratio  of  about  3  or  4:  i.  The  principal  inorganic  salts  are  sodium 
salts  (chloride  and  carbonate),  whereas  the  phosphates  of  potassium, 
calcium,  magnesium  and  iron  are  present  in  smaller  amount. 

Substances  which  stimulate  the  flow  of.  lymph  are  termed  lympha- 

1Leary:  Private  communication. 


BLOOD   AND    LYMPH  263 

gogues.  Such  substances .  as  sugar,  urea,  certain  salts  (especially 
sodium  chloride),  peptone,  egg  albumin,  extracts  of  dogs'  liver  and 
intestine,  crab  muscles  and  blood  leeches  are  included  in  this  class. 

In  a  fasting  animal,  the  lymph  coming  from  the  intestine  is  a  clear, 
transparent  fluid  possessing  the  characteristics  already  outlined.  After 
a  meal  containing  fat  has  been  ingested,  this  intestinal  lymph  is  white 
or  "  milky."  This  is  termed  chyle  and  is  essentially  lymph  possessing  an 
abnormally  high  (5-15  per  cent)  content  of  emulsified  fat.  This  chyle 
is  absorbed  by  the  lacteals  of  the  intestine  and  transported  to  the  lower 
portion  of  the  thoracic  duct.  Apart  from  the  fat  value,  the  composition 
of  lymph  and  chyle  are  similar. 

EXPERIMENTS  ON  BLOOD 
I.  Defibrinated  Ox-blood  " 

1.  Reaction. — Moisten  red  and  blue  litmus  papers  with  10  per  cent  sodium 
chloride  solution  and  test  the  reaction  of  the  defibrinated  blood.    Test  by  Congo 
red  paper  also. 

2.  Microscopical  Examination. — Examine  a  drop  of  defibrinated  blood  under 
the  microscope.    Compare  the  objects  you  observe  with  Plate  IV,  opposite  page 
252.    Repeat  the  test  with  a  drop  of  your  own  blood. 

3.  Specific  Gravity. — Determine  the  specific  gravity  of  defibrinated  blood 
by  means  of  an  ordinary  specific  gravity  swindle.    Compare  this  result  with 
the  specific  gravity  as  determined  by  Hammerschlag's  method  in  the  next 
experiment. 

4.  Specific  Gravity  by  Hammerschlag's  Method. — Fill  an  ordinary  urinom- 
eter  cylinder  about  one-half  full  of  a  mixture  of  chloroform  and  benzene,  having 
a  specific  gravity  of  approximately  1.050.    Into  this  mixture  allow  a  drop  of  the 
blood  under  examination  to  fall  from  a  pipette  or  directly  from  the  finger  in  case 
fresh  blood  is  being  examined.    Care  must  be  taken  not  to  use  too  large  a  drop 
of  blood  and  to  keep  the  drop  from  coming  into  contact  with  the  walls  of  the  cyl- 
inder.   If  the  blood  drop  sinks  to  the  bottom  of  the  vessel,  thus  shdwing  it  to  be 
of  higher  specific  gravity  than  the  surrounding  fluid,  add  chloroform  until  the 
blood  drop  remains  suspended  in  the  mixture.    Stir  carefully  with  a  glass  rod 
after  adding  the  chloroform.    If  the  blood  drop  rises  to  the  surface  upon  being 
introduced  into  the  mixture,  thus  showing  it  to  be  of  lower  specific  gravity  than  the 
surrounding  fluid,  add  benzene  until  the  blood  drop  remains  suspended  in  the 
mixture.    Stir  with  a  glass  rod  after  the  benzene  is  added.    After  the  blood 
drop  has  been  brought  to  a  suspended  position  in  the  mixture  by  means  of  one  or 
more  additions  of  chloroform  and  benzene  this  final  mixture  should  be  filtered 
through  muslin  and  its  specific  gravity  accurately  determined.    What  is  the 
specific  gravity  of  the  blood  under  examination? 

5.  Tests  for  Various  Constituents. — Place  10  c.c.  of  defibrinated  blood  in  an 
evaporating  dish,  dilute  with  50  c.c.  of  water  and  heat  to  boiling.     Is  there  any 
coagulation,  and  if  so  what  bodies  form  the  coagulum?    At  the  boiling-point 
add  about  50  c.c.  of  very  dilute  acetic  acid  (made  by  adding  2  drops  of  36  per  cent 
acetic  acid  to  50  c.c.  of  water)  and  again  heat  to  boiling  for  a  few  moments. 


264 


PHYSIOLOGICAL   CHEMISTRY 


Filter.  The  filtrate  should  be  clear  and  the  coagulum  dark  brown.  Reserve 
this  coagulum.  What  body  gives  the  coagulum  this  color?  Evaporate  the 
filtrate  to  about  25  c.c.,  filtering  off  any  precipitate  which  may  form  in  the  process. 
Make  the  following  tests  upon  the  filtrate : 

(a)  Fehling's  Test— To  5  c.c.  of  the  neutralized  filtrate  add  5  drops  of  Feh- 
ling's  solution  and  boil  one  minute. 

(b)  Chlorides. — To  a  small  amount  of  the  filtrate  in  a  test-tube  add  a  few 
drops  of  nitric  acid  and  a  little  silver  nitrate.    In  the  presence  of  chloride,  a  white 
precipitate  of  silver  chloride  will  form. 

(c)  Phosphates. — Test  for  phosphates  by  nitric  acid  and  molybdate  solution 
according  to  directions  given  on  page  58. 

(d)  Crystallization  of  Sodium  Chloride. — Place  the  remainder  of  the  filtrate 
in  a  watch  glass  and  evaporate  it  on  a  water-bath.    Examine  the  crystals  under 
the  microscope  and  compare  them  with  those  in  Fig.  86,  page  269. 

6.  Test  for  Iron. — Incinerate  a  small  portion  of  the  coagulum  from  the  last 
experiment  (5)  in  a  porcelain  crucible.  Cool,  dissolve  the  residue  in  dilute  hy- 
drochloric acid  and  test  for  iron  by  potassium  ferrocyanide  or  ammonium  thio- 
cyanate.  Which  of  the  constituents  of  the  blood  contains  the  iron? 


FIG.  83. — EFFECT  OF  WATER  ON  ERYTHROCYTES. 

7.  Hemolysis  ("Laky  Blood"). — Note  the  opacity  of  ordinary  defibrinated 
blood.    Place  a  few  cubic  centimeters  of  this  blood  in  a  test-tube  and  add  water, 
a  little  at  a  time,  until  the  blood  is  rendered  transparent.    Hemolysis  has  taken 
place.    How  does  the  water  act  in  causing  this  transparency?    Examine  a  drop 
of  hemolyzed  blood  under  the  microscope.    How  does  its  microscopical  appear- 
ance differ  from  that  of  unaltered  blood?    What  other  agents  may  be  used  to 
bring  about  hemolysis? 

8.  Osmotic  Pressure. — Place  a  few  cubic  centimeters  of  blood  in  each  of 
three  test-tubes.    Hemolyze  the  blood  in  the  first  tube  according  to  directions 
given  in  the  last  experiment  (7) :  add  an  equal  volume  of  isotonic  (0.9  per  cent) 
sodium  chloride  to  the  blood  in  the  second  tube,  and  an  equal  volume  of  10  per 
cent  sodium  chloride  to  the  blood  in  the  third  tube.    Mix  thoroughly  by  shaking 
and  after  a  few  moments  examine  a  drop  from  each  of  the  three  tutfes  under  the 


BLOOD   AND   LYMPH  265 

microscope  (see  Figs.  83  and  156,  pages  264  and  490).    What  do  you  find  and 
what  is  your  explanation  from  the  standpoint  of  osmotic  pressure? 

9.  Hemagglutination. — The   common   garden  bean,   such   as  the 
Scarlet  Runner,1   contains   a  protein  substance  which   exhibits  the 
interesting  property  of  causing  a  clumping  or  agglutination  of  red 
blood  corpuscles.2 

Dilute  defibrinated  blood3  ten  times  with  physiological  sodium  chloride  solu- 
tion (0.9  per  cent)  and  place  i  c.c.  in  each  of  three  small  test-tubes. 

Grind  three  beans  in  a  coffee  mill,  or  with  mortar  and  pestle  to  a  fine  meal 
and  extract  for  a  few  minutes  with  0.9  per  cent  sodium  chloride  solution.  Filter 
and  add  0.05  c.c.  (about  2-3  drops)  of  the  filtered  extract  to  the  first  of  the  blood 
tubes ;  o.oi  c.c.  to  the  second ;  and  0.05  c.c.  of  0.9  per  cent  sodium  chloride  to 
the  third. 

Invert  each  tube  to  mix  the  contents  thoroughly,  and  note  the  rapid  agglutina- 
tion and  precipitation  of  the  blood  corpuscles  hi  the  first  tube,  a  less  rapid  agglu- 
tination in  the  second,  while  the  third  or  control  tube  remains  unaltered.  In 
one-half  hour  the  corpuscles  hi  the  first  tube  often  are  packed  solid  and  one  is 
able  to  pour  off  perfectly  clear  serum. 

If  the  remainder  of  the  bean  extract  is  boiled  for  a  few  minutes,  the  coagulum 
filtered  out  and  0.05  c.c.  of  the  filtrate  added  to  the  control  tube,  still  no  agglutina- 
tion occurs,  indicating  that  the  hemagglutinin  has  been  destroyed  or  removed 
by  the  boiling. 

10.  Diffusion  of  Hemoglobin. — Prepare  some  hemolyzed  ("laky")  blood, 
thus  liberating  the  hemoglobin  from  the  erythrocytes.    Test  the  diffusion  of  the 
hemoglobin  by  preparing  a  dialyzer  like  one  of  the  models  shown  in  Fig.  2,  page 
24.    How  does  hemoglobin  differ  from  other  well-known  crystallizable  bodies? 

11.  Guaiac  Test. — By  means  of  a  pipette  drop  an  alcoholic  solution  of  guaiac 
(strength  about  i  :6o)4  or  the  Lyle-Curtman  guaiac  reagent5  (see  p.  237)  into 
the  solution  under  examination6  until  a  turbidity  is  observed  and  add  old  tur- 
pentine or  hydrogen  peroxide,  drop  by  drop-,  until  a  blue  color  is  obtained. 

In  the  detection  of  small  amounts  of  blood  the  quantity  of  guaiac 
used  should  also  be  decreased.  Do  any  other  substances  respond  in  a 
similar  manner  to  this  test?  Is  a  positive  guaiac  test  a  sure  indication 
of  the  presence  of  blood?  (See  discussion  on  page  261.) 

1  The  Scarlet  Runner  is  a  familiar  variety  purchasable  in  every  seed  store.    It  occurs  in 
two  varieties,  the  white  and  the  red.    Ricin,  a  protein  constituent  of  the  castor  bean,  also 
possesses  pronounced  agglutinating  properties.     Because  of  its  poisonous  nature  it  is,  how- 
ever, not  suitable  for  use  in  class  experiments. 

2  Mendel:  Archimo  di  fisiologia,  7,  168,  1909;  Schneider:  Journal  Biol.  Chem.,  11,47, 
1912. 

3  Rabbit's  blood  is  especially  desirable  (Mendel:  loc.  cit.}  and  may  be  obtained  for  the 
purpose  by  bleeding  from  a  small  cut  on  the  animal's  ear  and  defibrinating, 

4  Buckmaster  advises  the  use  of  an  alcoholic  solution  of  guaiaconic  acid  instead  of  an 
alcoholic  solution  of  guaiac  resin. 

5Lyle  and  Curtman;  Jour.  Biol.  Chem.,  33,  i,  1918. 

6  Alkaline  solutions  should  be  made  slightly  acid  with  acetic  acid,  as  the  blue  end- 
reaction  is  very  sensitive  to  alkali. 


266  PHYSIOLOGICAL  CHEMISTRY 

12.  Ortho-tolidin  Test  (Ruttan  and  Hardisty).1 — To  i  c.c.  of  a  4  per  cent 
glacial  acetic  acid  solution  of  o-tolidin^in  a  test-tube  add  i  c.c.  of  the  solution 
under  examination  and  i  c.c.  of  3  per  cent  hydrogen  peroxide.    In  the  presence 
of  blood  a  bluish  color  develops  (sometimes  rather  slowly)  and  persists  for  some 
time  (several  hours  in  some  instances). 

This  test  is  said  to  be  as  sensitive  for  the  detection  of  occult  blood 
in  feces  and  stomach  contents  as  is  the  benzidine  reaction.  It  is  also 
claimed  to  be  more  satisfactory  for  urine  than  any  other  blood  test. 
The  acetic  acid  solution  may  be  kept  for  one  month  with  no  reduction 
in  delicacy. 

13.  Benzidine  Reaction. — This  is  one  of  the  most  delicate  of  the 
reactions  for  the  detection  of  blood.     Different  benzidine  prepara- 
tions vary  greatly  in  their  sensitiveness,  however.     Inasmuch  as  ben- 
zidine solutions  change  readily  upon  contact  with  light  it  is  essential 
that  they  be  kept  in  a  dark  place. 

The  test  is  performed  as  follows:  To  a  saturated  solution  of  benzidine  in 
alcohol  or  glacial  acetic  acid  add  an  equal  volume  of  3  per  cent  hydrogen  peroxide 
and  i  c.c.  of  the  solution  under  examination.  If  the  mixture  is  not  already  acid 
render  it  so  with  acetic  acid,  and  note  the  appearance  of  a  green  or  blue  color. 
A  control  test  should  be  made  substituting  water  for  the  solution  under 
examination. 

The  hemoglobin  decomposes  the  hydrogen  peroxide  (catalysis)  and 
the  liberated  oxygen  oxidizes  the  benzidine.  The  sensitiveness  of  the 
benzidine  reaction  is  greater  when  applied  to  aqueous  solutions  than 
when  applied  to  the  urine.  According  to  Ascarelli3  the  benzidine  reac- 
tion serves  to  detect  blood  when  present  in  a  dilution  of  1:3,000,000. 
Walter4  has  also  shown  the  test  to  be  very  delicate,  and  claims  it  to  be 
more  satisfactory  than  the  guaiac  test. 

Lyle,  Curtman  and  Marshall5  have  investigated  the  benzidine 
reaction  very  carefully.  They  suggest  a  new  procedure  in  preparing  the 
reagent  and  in  conducting  the  test. 

The  test  follows:  Into  a  perfectly  clean  dry  test-tube  introduce  1.4  c.c. 
benzidine  solution,6  add  0.2  c.c.  of  water  or  glacial  acetic  acid,  then  i  c.c.  of  the 

1  Ruttan  and  Hardisty:  Canadian  Medical  Ass' n  Journal,  Nov.,  1912;  also  Biochemical 
Bull.,  2,  225,  1913. 

2NH2  NH7 

CeH4—  CeEU. 

CH,  CH8 

3  Ascarelli:  //  policlin  sez.  prat.,  19.09. 

4  Walter:  Deut.  med.  Woch.,  36,  p.  309. 

6  Lyle,  Curtman  and  Marshall:  Jour.  Biol.  Chem.,  19,  445,  1914. 

6  Benzidine  solution  may  be  prepared  as  follows:  Place  4.33  c.c.  of  glacial  acetic  acid  in 
a  small  Erlenmeyer  flask,  warm  to  50°  and  add  0.5  gram  of  benzidine.  Heat  the  flask  for 
eight  to  ten  minutes  in  water  at  50°.  To  the  resultant  solution  add  19  c.c.  of  distilled 
water.  This  solution  may  be  kept  for  several  days  without  deterioration.  %- 


BLOOD   AND    LYMPH  267 

fluid  to  be  tested  and  finally  0.4  c.c.  of  3  per  cent  hydrogen  peroxide.    Note  the 
appearance  of  a  blue  color,  which  reaches  its  maximum  in  five  to  six  minutes. 

The  acetic  acid  keeps  the  benzidine  in  solution.  An  excess  dimin- 
ishes the  delicacy  of  the  reagent. 

Hydrogen  peroxide  supplies  oxygen  for  the  reaction  and  also  bleaches 
the  blue  color.  An  excess  of  peroxide  interferes  with  the  reaction  by 
destroying  the  catalytic  power  of  the  blood  and  by  reacting  with  the 
benzidine  itself,  with  the  formation  of  products  which  appear  to  have 
an  inhibitory  action.  It  is  very  essential  that  the  peroxide  be  added 
last. 

The  benzidine  solution  should  be  dilute.  Such  solutions  are  exceed- 
ingly sensitive  and  permit  the  detection  of  blood  when  present  in  ratio 
i :  5,000,000. 

Gregersen  and  Boas1  claim  that  the  uses"~of  a  too  concentrated 
benzidine  solution  may  lead  to  wrong  diagnosis  because  of  the  excessive 
sensitiveness  of  the  reagent.  The  feces  of  normal  persons  on  a  meat- 
free  diet  often  yield  a  positive  reaction.  They  suggest  the  use  of  a 
0.5  per  cent  benzidine  solution  and  the  replacement  of  the  hydrogen 
peroxide  by  barium  peroxide  which  is  much  more  stable.  They, 
however,  admit  that  slight  hemorrhages  may  go  undiscovered  when 
this  dilute  benzidine  solution  is  used. 

14.  Hemin  Test. — (a)  Teichmann's  Method. — Place  a  very  small  drop  of 
blood  on  a  microscopic  slide,  add  a  minute  gram  of  sodium  chloride2  and  care- 
fully evaporate  to  dryness  over  a  low  flame.  Put  a  cover-glass  hi  place,  run 
underneath  it  a  drop  of  glacial  acetic  acid  and  warm  gently  until  the  formation  of 
gas  bubbles  is  noted.  Add  another  drop  of  glacial  acetic  acid,  cool  the  prepara- 
tion, examine  under  the  microscope  and  compare  the  crystals  with  those  shown  in 
Figs.  84  and  85. 

The  hemin  crystals  result  from  the  decomposition  of  the  hemoglobin 
of  the  blood.  What  are  the  steps  involved  in  this  process?  The  hemin 
crystals  are  also  called  Teichmann's  crystals.  Is  this  an  absolute  test 
for  blood?  Is  it  possible  to  differentiate  between  human  blood  and  the 
blood  of  other  species  by  means  of  the  hemin  test? 

(b)  Nippe's  Method.3 — Spread  a  small  drop  of  blood  on  a  slide  hi  the  form  of 
a  film  and  evaporate  to  dryness  over  a  low  flame.  Now  add  2  drops  of  a  solution 
containing  o.i  gram  each  of  potassium  chloride,  iodide  and  bromide  hi  100  c.c. 
of  glacial  acetic  acid.  Place  a  cover-glass  hi  position  and  heat  gently  over  a  low 
flame  until  gas  bubbles  form  and  the  solution  boils.  Run  1-2  drops  of  the  re- 
agent underneath  the  cover-glass  and  examine  under  a  microscope.  Compare 
the  crystals  with  those  shown  hi  Figs.  84  and  85. 

1Boas:  Berl.  klin.  Woch.,  56,  939,  1919. 

2  Buckmaster  considers  the  use  of  potassium  chloride  preferable. 

3  Nippe:  Deut.  med.  Woch.,  38,  2222,  1912. 


268 


PHYSIOLOGICAL  CHEMISTRY 


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FIG.  84. — HEMIN  CRYSTALS  FROM  HUMAN  BLOOD. 

Reproduced  from  a  micro-photograph  furnished  by  Prof .  E.  T.  Reichert,  of  the  University 

of  Pennsylvania. 


r:  •**>=* 


FIG.  85. — HEMIN  CRYSTALS  FROM  SHEEP  BLOOD. 

Reproduced  from  a  micro-photograph  furnished  by  Prof.  E.  T.  Reichert,  of  the  University 

of  Pennsylvania. 


BLOOD   AND    LYMPH 


269 


This  method  is  more  rapid  than  Teichmann's  method  and  crystals 
of  inorganic  chlorides  are  not  formed.  In  Teichmann's  method  crystals 
of  sodium  chloride  often  obscure  the  hemin  crystals. 

15.  Catalytic  Action. — To  about  10  drops  of  blood  in  a  test-tube  add  twice  the 
volume  of  hydrogen  peroxide,  without  shaking.    The  mixture. foams.    What  is 
the  cause  of  this  phenomenon? 

16.  Crystallization  of  Oxyhemoglobin.    Reichert's  Method. — Add  to  5  c.c. 
of  the  blood  of  the  dog,  horse,  guinea-pig,  or  rat,  before  or  after  laking,  or  de- 
fibrinating,  from  i  to  5  per  cent  of  ammonium  oxalate  in  substance.    Place  a 
drop  of  this  oxalated  blood  on  a  slide  and  examine  under  the  microscope.    The 
crystals  of  oxyhemoglobin  will  be  seen  to  form  at  once  near  the  margin  of  the 
drop,  and  in  a  few  minutes  the  entire  drop  may  be  a  solid  mass  of  crystals. 
Compare  the  crystals  with  those  shown  in  Figs.  76  to  82,  pages  254^0  257. 


FIG.  86. — SODIUM  CHLORIDE. 

17.  Preparation  of  Hematin. — Place  100  c.c.  of  hemolyzed  (laked)f\>\ood  in  a 
beaker  and  add  95  per  cent  alcohol  until  precipitation  ceases.     What  bodies  are 
precipitated?    Transfer  the  precipitate  to  a  flask  and  boil  with  95  per  cent  alcohol 
previously  acidulated  with  sulphuric  acid.    Through  the  action  of  the  acid  the 
hemoglobin  is  split  into  hematin  and  a  protein  body  called  globin.    Later  the 
"sulphuric  acid  ester  of  hematin"  is  formed,  which  is  soluble  in  the  alcohol.     Con- 
tinue heating  until  the  precipitate  is  no  longer  colored,  then  filter.     Partly  saturate 
the  nitrate  with  sodium  chloride  and  warm.     In  this  process  the  "hydrochloric  acid 
ester  of  hematin"  is  formed.     Filter  and  dissolve  on  the  filter  paper  by  sodium 
carbonate.     Save  this  alkaline  solution  of  hematin  and  make  a  spectroscopic  ex- 
amination later  after  becoming  familiar  with  the  use  of  the  spectroscope.     How 
does  the  spectrum  of  oxyhemoglobin  differ  from  that  of  the  derived  alkali  hematin? 

18.  Preparation  of  Thrombin  (Howell).3 — Prepare  fibrin  from  pig's  blood 
according  to  directions  given  on  page  271.    Wash  the  fibrin  thoroughly  in  water 

1  Care  should  be  taken  not  to  add  too  great  an  excess  of  these  reagents. 
'This  process  insures  constancy  of  temperature  and  strength  of  reagents. 
3  Howell:  Am.  Jour.  PhysioL,  32,  264.  1913. 


2  JO  PHYSIOLOGICAL   CHEMISTRY 

to  remove  hemoglobin.  Squeeze  out  the  water,  mince  the  fibrin  and  cover  with 
an  8  per  cent  sodium  chloride  solution  and  allow  to  stand  in  the  cold  for  48  hours. 
Filter.  Precipitate  the  thrombin  (and  other  proteins)  from  the  filtrate  by  adding 
an  equal  volume  of  acetone.  Filter  the  mixture  rapidly  through  a  number  of 
small  (25-50  c.c.)  filters.  Spread  out  filter  papers  and  precipitate  and  dry  rapidly 
in  a  current  of  cold  air.  Cut  the  dried  papers  into  small  pieces  and  treat  with  a 
volume  of  water  equivalent  to  66  per  cent  of  the  8  per  cent  NaCl  previously  used. 
Allow  to  stand  one-half  hour  and  filter.  Shake  the  filtrate  with  chloroform 
(10-15  c.c.  per  100  c.c.  filtrate)  until  on  settling  no  opalescence  is  developed  by 
heating  a  portion  of  the  supernatant  fluid.  Decant  the  liquid  and  evaporate 
on  watch  glasses  (2  c.c.  to  a  watch  glass)  in  a  current  of  air.  Thrombin  so  pre- 
pared may  be  kept  indefinitely  in  a  desiccator. 

19.  Variation  in  Size  of  Erythrocytes. — Prepare  two  small  funnels  with  filter 
papers  such  as  are  used  in  quantitative  analysis.  Moisten  each  paper  with  physio- 
logical (isotonic)  salt  solution.  Into  one  funnel  introduce  a  small  amount  of 
denbrinated  ox  blood  and  into  the  other  funnel  allow  blood  to  drop  directly  from  a 
decapitated  frog.  Note  that  the  nitrate  from  the  ox  blood  is  colored,  whereas  that 
from  the  frog  blood  is  colorless.  What  deduction  do  you  make  regarding  the 
relative  size  of  the  erythrocytes  in  ox  and  frog  blood?  Does  either  nitrate  clot? 
Why? 

II.  Blood  Serum1 

1.  Coagulation  Temperature. — Place  5  c.c.  of  undiluted  serum  in  a  test-tube 
and  determine  its  temperature  of  coagulation  according  to  the  method  described 
on  page  104.    Note  the  temperature  at  which  a  cloudiness  occurs  as  well  as  the 
temperature  at  which  coagulation  is  complete. 

2.  Precipitation  by  Alcohol. — To  5  c.c.  of  serum  in  a  test-tube  add  twice  the 
amount  of  95  per  cent  alcohol  and  thoroughly  mix  by  shaking.    What  is  this  pre- 
cipitate?   Make  a  confirmatory  test.    Test  the  alcoholic  filtrate  for  protein. 
Explain  the  result. 

3.  Proteins  of  Blood  Serum. — Place  about  10  c.c.  of  serum  in  a  small  evapo- 
rating dish,  dilute  with  5  c.c.  of  water  and  heat  to  boiling.    At  the  boiling-point 
acidify  slightly  with  dilute  acetic  acid.    Of  what  does  this  coagulum  consist? 
Filter  off  the  coagulum  (reserve  the  filtrate)  and  test  it  as  follows : 

(a)  Millon's  Reaction. — Make  the  test  according  to  directions  given  on  page 

97- 

(b)  Hopkins-Cole  Reaction. — Make  the  test  according  to  directions  given  on 

page  98. 

4.  Sugar  in  Serum. — To  5  c.c.  of  the  neutralized  filtrate  from  Experiment  3 
add  5  drops  of  Fehling's  solution  and  boil  one  minute.    What  do  you  conclude? 

5.  Detection  of  Sodium  Chloride.— (a)  Test  a  little  of  the  filtrate  from  Ex- 
periment 3  for  chlorides,  by  the  use  of  nitric  acid  and  silver  nitrate,     (b)  Evapo- 
rate 5  c.c.  of  the  filtrate  from  Experiment  3  in  a  watch  glass  on  a  water-bath. 
Examine  the  crystals  and  compare  them  with  those  reproduced  in  Fig.  86,  p.  269. 

6.  Separation  of  Serum  Globulin  and  Serum  Albumin. — Place  10  c.c.  of  blood 
serum  in  a  small  beaker  and  saturate  with  magnesium  sulphate.    What  is 
this  precipitate?    Filter  it  off  and  acidify  the  filtrate  slightly  with  acetic  acid. 
What  is  this  second  precipitate?    Filter  this  precipitate  off  and  test  the  filtrate  by 
the  biuret  test.    What  do  you  conclude? 

1  For  directions  as  to  preparation  of  serum,  see  "Reagents  and  Solutions."     (Page  631.) 

m  * 


BLOOD   AND    LYMPH  271 

in.  Blood  Plasma 

i.  Preparation  of  Oxalated  Plasma.— Allow  arterial  blood  to  run  into  an  equal 
volume  of  0.2  per  cent  ammonium  oxalate  solution. 

2  Preparation  of  Fibrinogen.— To  25  c.c.  of  oxalated  plasma  add  an  equal 
volume  of  saturated  sodium  chloride  solution.    Note  the  precipitation  of  fibrino- 
gen.    Filter  off  the  precipitate  (reserve  the  filtrate)  and  test  it  by  a  protein  color 

test  (see  page  97). 

3  Effect  of  Calcium  Salts.— Place  a  small  amount  of  oxalated  plasma  in  a 
test-tube  and  add  a  few  drops  of  a  2  per  cent  calcium  chloride  solution.    What 
occurs?    Explain  it. 

4  Preparation  of  Salted  Plasma.— Allow  arterial  blood  to  run  into  an  equal 
volume  of  a  saturated  solution  of  sodium  sulphate  or  a  10  per  cent  solution  of 
sodium  chloride.    Keep  the  mixture  in  a  cool  place  for  about  24  hours. 

5.  Effect  of  Dilution.— Place  a  few  drops  of  salted  plasma  in  a  test-tube 
and  dilute  it  with  10-15  volumes  of  water.    What  do  you  observe?    Explain  it. 

IV.  Fibrin 

1.  Preparation  of  Fibrin.— Allow  blood  to  flow  directly  from  the  animal  into 
a  vessel  and  rapidly  whip  it  by  means  of  a  bundle  of  twigs,  a  mass  of  strong  cords, 
or  a  specially  constructed  beater.    If  a  pure  fibrin  is  desired  it  is  not  best  to 
attempt  to  manipulate  a  large  volume*of  blood  at  one  time.    After  the  fibrin  has 
been  collected  it  should  be  freed  from  any  adhering  blood  clots  and  washed  in 
water  to  remove  further  traces  of  blood.    The  pure  product  should  be  very  light 
n  color.    It  may  be  preserved  under  glycerol,  dilute  alcohol,  or  chloroform  water. 

2.  Solubility.— Try  the  solubility  of  small  shreds  of  freshly  prepared  fibrin 
in  water,  dilute  acid  and  alkali. 

3.  Millon's  Reaction.— Make  the  test  according  to  directions  given  on  page 

7'4.  Glyoxylic  Acid  Reaction  (Hopkins-Cole). -Make  the  test  according  to 
directions  given  on  page  98. 

5.  Biuret  Test.— Make  the  test  according  to  directions  given  on  page  99. 

V.  Detection  of  Blood  in  Stains  on  Cloth,  Etc. 

1.  Identification  of  Corpuscles.— If  the  stain  under  examination  is  on  cloth 
a  portion  should  be  extracted  with  a  few  drops  of  glycerol  or  physiological  (0.9  per 
cent)  sodium  chloride  solution.    A  drop  of  this  solution  should  then  be  examined 
under  the  microscope  to  determine  if  corpuscles  are  present. 

2.  Tests  on  Aqueous  Extract.— A  second  portion  of  the  stain  should  be 
extracted  with  a  small  amount  of  water  and  the  following  tests  made  upon  the 

aqueous  extract: 

(a)  Hemochromogen.— Make  a  small  amount  of  the  extract  alkaline  by 
potassium  hydroxide  or  sodium  hydroxide,  and  heat  until  a  brownish-green  color 
results.    Cool  and  add  a  few  drops  of  ammonium  sulphide  or  Stokes'  reagent 
(see  page  300)  and  make  a  spectroscopic  examination.    Compare  the  spectrum, 
with  that  of  hemochromogen  (see  Absorption  Spectra,  Plate  II).    Hankin1  has 
suggested  a  test  based  upon  the  formation  of  cyanhempchromogen  and  the 
microspectroscopical  demonstration  of  the  spectrum  of  this  compound. 

(b)  Hemin  Test.— Make  this  test  upon  a  small  drop  of  the  aqueous  extract 
according  to  the  directions  given  on  page  267. 


272  PHYSIOLOGICAL   CHEMISTRY 

(c)  Guaiac  Test.— Make  this  test  on  the  aqueous  extract  according  to  the 
directions  given  on  page  265.    The  guaiac  solution  may  also  be  applied  directly 
to  the  stain  without  previous  extraction  in  the  following  manner :  Moisten  the 
stain  with  water,  and  after  allowing  it  to  stand  several  minutes,  add  an  alcoholic 
solution  of  guaiac  (strength  about   i :  60)  and  a  little  hydrogen  peroxide  or  old 
turpentine.    The  customary  blue  color  will  be  observed  in  the  presence  of  blood. 

(d)  Benzidine  Reaction. — Make  this  test  according  to  directions  given  on 
page  267. 

(e)  Acid  Hematin. — If  the  stain  fails  to  dissolve  in  water  extract  with  acid 
alcohol  and  examine  the  spectrum  for  absorption  bands  of  acid  hematin  (see 
Absorption  Spectra,  Plate  II). 

1  Hankin:  Brit.  Med.  Jour.,  p.  1261,  1906. 
Sutherland  and  Mitra:  Biochemical  Journal,  8,  128,  1914. 


* 


CHAPTER  XVI 


BLOOD  ANALYSIS 

THE  study  of  the  composition  of  the  blood  under  various  normal  and 
pathological  conditions  has  received  great  impetus  from  the  development 
of  methods  for  blood  analysis  which  require  but  small  amounts  of 
material  and  yet  give  accurate  results.  Many  facts  of  physiological 
as  well  as  clinical  importance  have  thus  been  made  available.  Some 
typical  examples  of  data  obtained  in  this  way  are  given  in  the  table  on 

COMPOSITION  OF  NORMAL  BLOOD  AND  OF  THE  BLOOD  IN  CERTAIN 
PATHOLOGICAL  CONDITIONS1 


Normal 

Chronic 
nephritis 

Uremia 

Early 
diabetes 

Severe 
diabetes 

Moderate 
acidosis 

Severe 
acidosis 

Gout 

Lipemia 

Cholelith- 
iasis 

A 

thr 

Total  solids, 
per  cent  

20.  o 

13-19 

12-18 

17-20 

10-21 

Total    N,    per 
cent  

3-0 

2.5-3-0 

1.7-2.7 

1.8-2.9 

60- 

Non-protein 

25-30 

30-90 

90-400 

25-35 

Urea  N  

12-15 

16-70          70-300 

• 

2- 

Uric  acid  

2-3 

3-10            4-25 

4—10 

Creatinine.  .  .  . 

1-2 

2-4               4-35 

Creatine  

3-7 

7-3O 

• 

• 

.    . 

Amino-acidN  . 

6-8 

8-30 



Ammonia  N..:  0.1-0.2 

O.I-O.2        O.  2-1.0 

Sugar,  per  cent 

0.08-0.12 

0.1-0.2 

0.14-0.30 

0.3-1.2 

— 

j  Acetone  + 
Acetoacetic 
acid  i       o-r.o 

2-25 

I.  5-12 

10-40 

0-hydroxy- 
butyric  acid. 

0-3.0 

5-25 

5-15 

10-100 



Alkali  reserve 
(c.c.    CO2    in 
TOO  c.c.  plas- 
ma   

77-53 

Below' 
40-30            30 

Cholesterol...     140-180      170-350      170-350 

150-300 

500-3600 

280-950 

|  

Chlorides      as 
NaCl,  per  cent     .0.65 

0.55-0.75  0.45-0   65 

0.60 

Acid      soluble 
phosphorus.  . 

2-6 

3-7                7-21 

Lipoid     phos- 
phorus   

'    6-12 

8-13 

8-30 

Pat,  per  cent. 

o.x-0.72 

3-18       

3-29 

Calcium 
(plasma)  .... 

•   10 

3-9 

i 

1  Results  are  expressed  as  milligrams  per  100  c.c.  of  blood  unless  otherwise  indi- 
cated.    Some  of  the  figures  given  are  based  upon  but  few  analyses  and  may  not  be  entirely 
characteristic. 

2  A  short  time  after  a  meal  rich  in  fat  the  blood  may  contain  considerably  more  fat. 

If.      i  §  273 


274  PHYSIOLOGICAL   CHEMISTRY 

p.  273.  The  data  there  tabulated  have  been  compiled  from  the  work 
of  many  observers.1 

It  will  be  noted  that  in  chronic  nephritis  the  principal  change  is  in 
the  urea  and  non-protein  nitrogen  of  the  blood  which  may  increase 
considerably.  In  severe  cases  associated  with  uremia  the  retention  of 
these  forms  of  nitrogen  may  be  very  great  and  there  is  a  consequent 
rise  in  the  blood  content  which  may  amount  to  1000  per  cent  or  more. 
In  uremia  there  is  likewise  a  great  increase  in  other  individual  nitroge- 
nous components  of  the  blood  such  as  uric  acid,  creatinine,  creatine, 
amino-acid  nitrogen,  and  even  of  ammonia.  The  increase  in  creatinine 
has  been  shown  by  Myers  and  Fine  and  others  to  be  significant,  inas- 
much as  this  increase  does  not  appear  to  occur  in  other  types  of  nephritis. 
Uric  acid  is  greatly  increased  in  uremia  and  may  be  very  much  higher 
than  in  gout.  Associated  with  uremia  there  is  ordinarily  an  acidosis. 
There  may  be  an  increase  in  the  sugar  of  the  blood  and  a  very  great 
increase  of  the  acetone  bodies  present.  An  increase  is  also  generally 
found  in  cholesterol  and  in  the  various  forms  of  phosphorus  of  the  blood, 
while  calcium  may  be  decreased. 

Determinations  of  non-protein  nitrogen  and  urea  are  also  of  great 
value  to  the  surgeon  in  determining  the  risk  of  operation,  especially 
in  cases  of  prostatic  obstruction. 

In  diabetes  the  most  noteworthy  changes  are  in  the  content  of  glucose 
and  of  acetone  bodies.  Glucose  may  be  increased  above  the  normal 
(about  o.i  per  cent)  to  0.15-0.80  per  cent.  The  increase  in  acetone, 
diacetic  acid  and  hydroxybutyric  acid  is  very  marked  in  comparison 
with  the  minute  amounts  found  in  normal  blood.  There  may  also  be 
an  increase  in  fat  and  other  lipoids  in  severe  diabetes. 

On  the  other  hand  in  the  condition  known  as  renal  diabetes  glucose 
is  found  in  the  urine  without  symptoms  of  diabetes  mellitus  and  with  a 
normal  blood  sugar. 

In  moderate  acidosis  the  " alkali  reserve"  measured  in  terms  of 
carbon  dioxide  may  range  from  40  to  30  volumes  per  cent,  whereas 
values  below  30  are  met  with  in  severe  acidosis  (see  Chapter  XVII) . 

In  gout  the  characteristic  change  is  in  the  uric  acid  content  which  is 
almost  always  considerably  increased.  Other  forms  of  nitrogen  are 

1The  following  may  be  particularly  mentioned:  Myers  and  Fine:  Jour.  Biol.  Chem., 
20,  391,- 1915;  Post-Graduate,  1914-15;  reprinted  as  "Chemical  Composition  of  the  Blood 
in  Health  and  Disease,"  New  York,  1915;  Folin  and  Denis:  Jour.  Biol.  Chem.,  14,  29, 
1913;  13,  469,  1913;  17,  487,  1914;  Arch.  Int.  Med.,  16,  33,  1915;  Christian,  Frothingham 
and  Wood:  Am.  J.  Med.  Sci.,  150,  655,  1915;  Greenwald:  Jour.  Biol.  Chem.,  21,  29,  1915; 
Van  Slyke  and  Meyer:  Jour.  Biol.  Chem.,  12,  399,  1912;  Bloor:  Jour.  Biol.  Chem,,  23, 
317,  1915;  Marriott:  Jour.  Biol.  Chem.,  16,  293,  1913;  18,  507,  1914;  Gettler  and  Baker: 
Jour.  Biol.  Chem.,  25,  211,  1916;  Bock:  Jour.  Biol.  Chem.,  29,  191, 1917;  Wilson  and  Plass: 
Jour.  Biol.  Chem.,  29,  413,  1917;  Barnett:  Jour.  Biol.  Chem.,  29,  459,  1917;  Hunter  and 
Campbell:  Jour.  Biol.  Chem.,  33,  169,  1918;  Stillman,  Van  Slyke,  Cullen  and  Fitz:  Jour. 
Biol.  Chem.,  30,  405,  1917. 


:  Jour. 


BLOOD   ANALYSIS  275 

affected  but  little.  In  arthritis  the  blood  may  also  be  high  in  uric  acid 
but  in  this  case  ordinarily  there  is  a  rise  in  non-protein  nitrogen  also, 
indicating  perhaps  an  associated  nephritis  in  such  cases. 

Lipemia  is  usually  associated  with  an  increased  sugar  content  of  the 
blood.  The  fat  content  in  this  condition  has  been  found  as  high  as  29 
per  cent.  There  is  a  correspondingly  large  increase  in  the  cholesterol 
of  the  blood. 

In  cholelithiasis  there  appears  generally  to  be  a  fairly  marked 
increase  in  the  cholesterol  content  of  the  blood  and  this  determination 
is  thus  of  diagnostic  aid.  Some  increase  may  also  be  found  in  other 
disorders  as  in  nephritis,  severe  diabetes,  pregnancy,  arteriosclerosis 
and  syphilis,  and  marked  decreases  have  been  noted  in  pernicious 


anemia.1 


METHODS 


The  Drawing  of  Blood  for  Analysis. — A  tourniquet  (of  soft,  firm  rubber 
tubing  or  a  strip  of  bandage)  is  drawn  tightly  about  the  arm  of  the  patient  a 
couple  of  inches  above  the  elbow.  The  fist  is  kept  firmly  clenched.  The  parts 
about  the  most  prominent  vein  (usually  the  median  basilic)  are  washed  with 
alcohol,  the  vein  is  held  immobile  by  the  thumb  of  the  operator,  and  a  sterile 
hypodermic  needle,  sharp  but  without  too  long  a  point,  (a  No.  18,  an  inch  and  a 
half  long  may  be  used),  inserted  into  the  vein,  at  an  angle  of  about  50°  with  the 
surface  of  the  arm,  the  opening  of  the  needle  being  kept  downward  or  to  the 
side.  Blood  is  allowed  to  flow  into  a  test  tube  containing  about  0.02  gm.  of 
powdered  potassium  oxalate  per  10  c.c.  of  tyood,  the  whole  being  immediately 
mixed  to  prevent  clotting.  Plasma  may  be  obtained  by  centrifugation. 

Blood  specimens  are  best  taken  in  the  morning  before  breakfast,  to 
minimize  the  influence  of  food  ingestion.  Specimens  should  be  kept 
in  the  ice  box  and  analyses  preferably  made  on  the  day  of  withdrawal. 
This  is  particularly  necessary  in  the  case  of  sugar,  which  decreases  in 
amount  on  standing.  Denis2  has  shown,  however,  that  at  least  for 
the  Folin  and  Wu  sugar  method  blood  may  be  preserved  for  four  days 
or  more  at  2o-33°C.,  if  one  drop  (1/30  c.c.)  of  commercial  formalin 
(40  per  cent)  solution  is  added  to  each  5  c.c.  of  blood. 

The  Blood  Analysis  System  of  Folin  and  Wu3 

By  this  system  we  may  determine  on  a  single  blood  nitrate  the 
following:  Non-protein  nitrogen,  urea,  uric  acid,  creatinine  and  creatine, 

1Myers:  "Practical  Chemical  Analysis  of  Blood,"  C.  V.  Mosby  Co.,  St.  Louis,  1921, 
should  be  consulted  for  a  more  detailed  discussion  of  clinical  findings,  references  to  the 
literature,  etc. 

2  Denis,  W.:  Jour.  Biol.  Chem.,  44,  203,  1920. 

3  Folin  and  Wu:  Jour.  Biol.  Chem.,  38,  81,  1919. 


276 


PHYSIOLOGICAL  CHEMISTRY 


FIG.  87. 

DILUTING 

PIPETTE. 

(Folin 

and  Wu: 

Jour..  Biol. 

Chem., 

May, 

1919). 


sugar,  and  chlorides.  About  10  c.c.  of  blood  are  needed  for 
the  combined  determinations. 

i.  Preparation  of  the  Protein  Free  Blood  Filtrate.— 

Principle. — The  total  proteins  of  the  blood  are  removed 
by  precipitation  with  tungstic  acid  (formed  by  the  interac- 
tion of  sodium  tungstate  and  sulphuric  acid)  and  nitration. 
The  nitrate  contains  all  of  the  constituents  of  the  blood 
determined  by  this  system. 

Procedure. — To  prevent  coagulation  20  mgs.  of  potassium 
oxalate  per  10  c.c.  of  blood  should  have  been  used.  Use  of  much 
larger  amounts  of  oxalate  or  the  use  of  citrate  interferes  with 
deproteinization,  and  interferes  more  or  less  with  the  uric  acid 
determination. 

(  Transfer  a  measured  quantity  (5  to  15  c.c.)  of  oxalated  blood 
to  a  flask  having  a  capacity  of  fifteen  to  twenty  times  that  of  the 
volume  taken.  Lake  the  blood  with  seven  volumes  of  water. 
Add  one  volume  of  10  per  cent  solution  of  sodium  tungstate1 
(Na2WO42H2O)  and  mix. 

Add  from  a  graduated  pipette  or  burette,  slowly  and  with  shaking 
one  volume  of  two-thirds  normal  sulphuric  acid.2  Close  the  mouth 
of  the  flask  with  a  rubber  stopper  and  shake.  If  tJM^jnditions  are 
right,  hardly  a  single  airlMtble  will  form  as  a  resi  ^Bthe  shaking. 
Let  stand  for  5  minutes ;  the^rior  of  the  coaguraH^Proually  changes 
from  bright  red  to  dark  brown.  If  this  change  in  color  does  not 
occur,  the  coagulation  is  incomplete,  usually  because  too  much 
oxalate  is  present.  In  such  an  emergency  the  sample  may  be 
saved  by  adding  10  per  cent  sulphuric  acid,  one  drop  at  a  time 
shaking  vigorously  after  each  drop,  and  continuing  until  there  is 
practically  no  foaming  and  until  the  dark  brown  color  has  set  in. 

Pour  the  mixture  on  a  filter  large  enough  to  hold  it  all.  This 
filtration  should  be  begun  by  adding  only  a  few  c.c.  of  the  mixture 
down  the  double  portion  of  the  filter  paper  and  withholding  the 
remainder  until  the  whole  filter  has  been  wet.  Then  the  whole  of 
the  mixture  is  poured  on  the  funnel  and  covered  with  a  watch  glass. 
If  the  filtration  is  made  as  described  the  very  first  portion  of  the 
filtrate  should  be  clear  as  water  and  no  re-filtering  is  necessary. 


1 A  IQ  'per  cent  solution  of  sodium  tungstate.  Some  sodium  tungstates, 
though  labeled  c.p.,  are  not  serviceable  for  this  work.  They  usually  contain 
too  much  sodium  carbonate.  The  c.p.  sodium  tungstate  made  by  the 
Primos  Chemical  Company,  Primos,  Pa.,  is  satisfactory. 

2  A  two-thirds  normal  sulphuric  acid  solution,  35  g.  of  concentrated  c.p. 
sulphuric  acid  diluted  to  a  volume  of  i  liter,  will  usually  be  found  to  be  cor- 
'rect;  but  it  is  advisable,  indeed  necessary,  to  check  it  up  by  titration.  The 
two-thirds  normal  acid  is  intended  to  be  equivalent  to  the  sodium  content  of 
the  tungstate  so  that  when  equal  volumes  are  mixed  substantially  the  whole 
of  the  tungstic  acid  is  set  free  without  the  presence  of  an  excess  of  sulphuric 
acid.  The  tungstic  acid  set  free  is  nearly  quantitatively  taken  up  by  the  pro- 
teins and  the  blood  nitrates  obtained  are,  therefore,  only  slightly  acid  to 
congo  red  paper. 


BLOOD    ANALYSIS  277 

It  will  be  noted  that  the  precipitation  is  not  made  in  volumetric 
flasks.  By  the  process  described  6  or  7  or  n  or  12  c.c.  of  blood  can  be 
used,  whereas  with  volumetric  flasks  one  is  compelled  to  use  5,  10  or 
20  c.c.,  because  flasks  suitable  for  other  volumes  are  not  available. 
Special  graduated  "  blood  pipets,"  made  by  the  Emil  Greiner  Co., 
New  York,  are  very  useful  for  the  measurement  of  the  blood,  the  tung- 
state  and  the  acid. 

The  protein  free  blood  filtrates  are  not  acid  enough  to  prevent 
bacterial  decomposition.  If  the  filtrates  are  to  be  kept  for  any  length 
of  time,  more  than  two  days,  some  preservative,  a  few  drops  of  toluene 
or  xylene  should  be  added. 

2.  Determination  of  Non-protein  Nitrogen. — Principle. — Nitrogen 
is  determined  in  a  portion  of  the  blood  filtrate  by  a  micro- Kjeldahl, 
using  a  sulphuric  and  phosphoric  acid  mixture  for  the  digestion,  the 
ammonia  formed  being  determined  colorimetrically  after  direct  Nessleri- 
zation  of  the  digestion  mixture. 

Procedure.— Transfer  5  c.c.  of  the  blood  filtrate  to  a  large  test  tube  (Pyrex) 
200  mm.  X  25  mm.,  preferably  graduated  at  35  c.c.  and  50  c.c.1  The  test  tube 
should  either  be  dry  or  rinsed  with  alcohol  to  reduce  the  danger  of  bumping. 
Add  i  c.c.  fcf  diluted  acid  mixture2  and  a  quartz  pebble.  Boil  vigorously  over  a 
micro  burner  until  the  characteristic  (^ise  fumes  begin  to  fill  the  tube.  This 
will  happen  in  from  3  to  7  minutes,  d^Bnding  on  the  size  of  the  flame.  When 
the  test  tube  is  nearly  full  of  fumes  rRTuce  the  flame  sharply  so  that  the  speed 
of  the  boiling  is  reduced  almost  to  the  vanishing  point.  Cover  the  mouth  of  the 
test  tube  with  a  watch  glass.  Continue  the  gentle  heating  for  2  minutes,  count- 
ing from  the  time  the  test  tube  became  filled  with  fumes.  If  the  oxidations  are 
not  visibly  finished  at  the  end  of  two  minutes  the  heating  must  be  continued  until 
the  solution  is  nearly  colorless.  Usually  the  solution  becomes  colorless  at  the 
end  of  20  to  40  seconds.  At  the  end  of  2  minutes  remove  the  flame  and  allow 
the  digestion  mixture  to  cool  for  70  to  90  seconds.  Then  add  15  to  25  c.c.  of 
water.  Cool  further  approximately  to  room  temperature  and  then  fill  to  the 
35  c.c.  mark  with  water.  Add  15  c.c.  of  Nessler's  solution  (see  final  section 
on  Reagents  and  Solutions).  Insert  a  clean  rubber  stopper  and  mix.  If  the 
solution  is  turbid,  centrifuge  a  portion  before  making  the  color  comparison  with 
the  standard. 

The  standard  most  commonly  required  is  0.3  mg.  of  N.  Add  3  c.c.  of  stand- 
ard ammonium  sulphate  solution  (containing  i  mg.  of  N  per  10  c.c.,  made  by 
dissolving  0.4716  gm.  of  specially  purified  ammonium  sulphate  (see  note  p.  511) 
in  one  liter  of  ammonia-free  distilled  water)  to  a  100  c.c.  volumetric  flask. 
Add  to  it  2  c.c.  of  the  phosphoric  sulphuric  acid  mixture,  to  balance  the  acid  in  the 

1  These  may  be  obtained  from  Emil  Greiner,  New  York. 

2  Made  by  diluting  regular  acid  mixture  with  an  equal  volume  of  water.     The  regular 
acid  mixture  is  made  as  follows:  To  50  c.c.  of  a  5  per  cent  copper  sulphate  solution  add 
300  c.c.  of  85  per  cent  phosphoric  acid  and  mix.     Add  100  c.c.  of  concentrated  sulphuric 
acid  free  from  the  least  trace  of  ammonia  and  mix.     Keep  well  protected  to  prevent  ab- 
sorption of  ammonia  from  the  air. 


278  PHYSIOLOGICAL   CHEMISTRY 

test  tube;  dilute  to  about  60  c.c.  and  add  30  c.c.  of  Nessler's  solution.  The 
unknown  and  the  standard  should  be  Nesslerized  simultaneously. 

Calculation. — If  the  standard  is  set  at  20  mm.  for  the  color  comparison, 
20  divided  by  the  reading  and  multiplied  by  0.3  gives  the  non-protein  nitrogen  in 
i  c.c.  of  blood,  because  0.5  e.c,  (the  amount  of  blood  represented  in  5  c.c.  of  the 
blood  filtrate)  Nesslerized  at  a^olume  of  50  c.e.  is  equivalent  to  i  c.c.  Nesslerized 
at  a  volume  of  100  c/c. 

The,  non-protein  nitrogen  per  100  c.c.  of  blood  is,  therefore,  20  divided  by  the 
reading  and  multiplied  by  30  (0.3  times  100). 

If  the  standard  containing  0.5  mg.  N  is  used  the  calculation  becomes  20, 
divided  by  R,  times  50. 

Alternate  Procedures. — Instead  of  Nesslerizing,  it  is  possible^  lo^distill  or 
aspirate  off  the  ammonia  into  standard  acid,  and  titrate  using  apparatus  of  the' 
types  used  in  the  micro -determinations  of  total  nitrogen  in  urine  (see  Chapter 
XXVII).  Stehle  has  suggested1  a  gasometric  method  along  the  line  of  his 
method  for  urea  in  urine  (see  Chapter  XXVII). 

Interpretation. — Normal  blood  contains  25-30  mgms.  of  non-pro- 
tein nitrogen  per  100  c.c.  In  early  interstitial  nephritis  values  of 
30-50  may  be  obtained,  and  in  severe  nephritis  much  higher  values,  up 
to  the  400  mgms.  occasionally  found  in  uremia. 

The  non-protein  nitrogen  of  the  blood  includes  nitrogen  present  in 
urea,  uric  acid,  creatinine,  ammonia,  and  other  substances.  The 
nitrogen  in  undetermined  forms  is  called  "rest  N"  and  makes  up  about 
46  per  cent  of  the  normal  non-protein  nitrogen.  In  uremia  this 
percentage  may  fall  to  20. 

3.  Determination  of  Urea. — Principle. — The  urea  is  decomposed  to 
ammonium  carbonate  by  means  of  the  enzyme  urease,  in  the  presence 
of  phosphate,  which  maintains  suitable  reaction  in  the  mixture.  The 
ammonia  is  distilled  off  and  determined  colorimetrically  after  Nessler- 
ization.  Alternate  aeration  and  autoclave  procedures-  are  given. 

Procedure.— /Transfer  5  c.c.  of  the  tungstic  acid  blood  filtrate  to  a  Pyrex 
ignition  tube  (200  X  25  mm.)  This  test  tube  must  be  rinsed  with  nitric  acid 
and  then  with  water  if  it  has  contained  Nessler  Solution.  Add  2  drops  of  buffer 
mixture2  and  then  introduce  i  c.c.  of  urease  solution.3  Immerse  the  test  tube 
in  warm  water,  40  to  55°C.,  and  leave  it  there  for  5  minutes,  or  let  stand  at  room 
temperature  for  15  minutes. 

The  ammonia  formed  from  the  urea  is  most  conveniently  obtained  by  distil- 
lation, without  a  condenser,  and  using  a  test  tube  graduated  at  25  c.c.  and  con- 

lJour.  Biol.  Chem.,  45,  223,  1920.  According  to  the  author,  the  pyrogallate  treatment 
may  be  dispensed  with  if  copper  sulphate  is  omitted. 

2  Made  by  dissolving  69  gm.  of  monosodium  phosphate  and  179  gm.  of  crystallized 
disodium  phosphate  in  800  c.c.  of  warm  distilled  water  and  diluting  to  one  liter. 

3  Urease  solution.     Wash  about  3  gm.  of  permutit  in  a  flask,  once  with  2  per  cent  acetic 
acid,  then  twice  with  water;  add  5  gm.  of  fine  jack  bean  meal  and  100  c.c.  of  15  per  cent 
alcohol.     Shake  gently  but  continuously  for  10-15  minutes,  pour  on  large  filter,  and  cover 
with  a  watch  glass.     The  solution  may  be  kept  about  a  week  at  room  temperature  or 
4-6  weeks  in  an  ice  box. 


BLOOD    ANALYSIS 


279 


taming  2  c.c.  of  0.05  N  hydrochloric  acid  as  the  receiver.    ^Xhe-iHustration  shows 
a  compact  and  convenient  arrangement  for  this  distillation.1 

Add  to  the  urease  blood  filtrate  a  dry  pebble,  a  drop  or  two  of  paraffin  oil 
and  2  c.c.  of  saturated  borax  solution.  Insert  firmly  the  rubber  stopper  carrying 
the  delivery  tube  and  receiver  and  then  boil  at  a  moderately  fast,  uniform  rate 
for  4  minutes.  The  size  of  the  flame  should  never  be  cut-down  during  the  distil- 
lation, nor  should  the  boiling  be  so  brisk  that  the  emission  of  steam  from  the 
receiver  begins  before  the  end  of  3  minutes.  At  the  end  of  4  minutes  slip  off 
the  receiver  from  the  rubber  stopper  and  let  it  rest  in  a 
slanting  position  while  the  distillation  is  continued  for  i 
more  minute.  Rinse  the  lower  end  of  the  delivery  tube 
with  a  little  water  and  cool  the  distillate  with  running  water 
and  dilute  to  about  20  c.c.  Transfer  0.3  mg.  N  (3  c.c.  of 
the  standard  ammonium  sulphate  solution)  to  a  100  c.c. 
volumetric  flask  and  dilute  to  about  75  c.c.  Nesslerize, 
using  10  c.c.  of  Nessler's  Solution  for  the  Standard,  and 
2.5  c.c.  for  the  unknown  in  the  test  tube.  Dilute  both  to 
volume  and  make  the  color  comparison.^) 

Calculation. — Divide  20  (the  height  of  the  standard  in 
mm.)  by  the  colorimetric  reading  and  multiply  *by  15. 
This  gives  the  urea  nitrogen  in  mgs.  per  100  c.c.  of  blood. 
In  explanation  of  this  calculation  it  is  to  be  noted  that  the 
unknown  representing  0.5  c.c.  of  blood,  is  Nesslerized  at 
25  c.c.,  whereas  in  the  case  of  the  non-protein  nitrogen  it 
is  Nesslerized  at  a  volume  of  50  c.c.  The  same  colori- 
metric reading,  therefore,  represents  only  one-half  as  much 
nitrogen  in  the  urea  determination  as  in  the  non-protein 
nitrogen  determination. 

Urea  Determination  by  Means  of  the  Autpclave. — When 
a  large  number  of  urea  determinations  are  to  be  made  or    may  be  cut  along  the 
when  creatin  determinations  are  also  made,  it  is  sometimes    side  of  the  stopper  of 

convenient  to  decompose  the  urea  of  the  blood  nitrate  by    the  receiving  tube  to 

,.    .      .  .      ,  ,,,  .  permit  the  escape  of 

heating  under  pressure.    To  5  c.c.  of  the  blood  nitrate  in  a    steam. 

large  test  tube  add  i  c.c.  of  normal  hydrochloric  acid,  cover 
with  tin  foil  and  heat  to  150°  for  10  minutes.     Distil  off  the  ammonia  exactly  as 
in  the  preceding  process,  except  that  2  c.c.  of  10  per  cent  sodium  carbonate  must 
be  substituted  for  the  borax,  because  of  the  added  hydrochloric  acid. 

Aeration  Process  in  Urea  Determination. — The  ammonia  formed  from  the 
blood  urea  by  urease,  or  by  heating  under  pressure,  can,  of  course  be,  driven 
into  the  receiver  by  an  air  current  plus  an  alkali,  instead  of  by  the  distillation 
process  described  above.  The  aeration  process  gives  perfectly  reliable  results,  if  a 
good  air  current  is  available. 

To  the  decomposed  blood  nitrate  in  a  large  test  tube  add  a  little  paraffin  oil 
and  i  or  2  c.c.  of  10  per  cent  sodium  hydroxide.  Connect  with  a  smaller  test  tube, 
marked  at  25  c.c.,  and  containing  2  c.c.  of  0.5  N  hydrochloric  acid.  The  connection 
is  made  as  in  the  aeration  process  for  urea  in  urine.  Pass  the  air  current  through 
rather  slowly  for  i  minute  and  then  nearly  as  fast  as  the  apparatus  can  stand  for 


FIG.  88.  —  APPA- 
RATUS FOR  DISTIL- 
LATION OF  AMMONIA 
FROM  UREA.  A, 
FIRST  POSITION.  B, 
SECOND  POSITION. 

(Folin  and  Wu: 
Jour.  Biol.  Chem., 


1  Watson  and  White  have  suggested  a  modification  of  this  apparatus.     See  Jour.  Biol. 
Chem.,  45,  465,  1921. 


280  PHYSIOLOGICAL   CHEMISTRY 

10  to  15  minutes.  Rinse  the  connecting  tube;  dilute  the  contents  of  the  receiver 
to  20  c.c.,  add  2.5  c.c.  of  Nessler  solution,  dilute  to  the  25  c.c.  mark,  and  make  the 
color  comparison  in  the  usual  manner. 

Interpretation. — Normally  from  12-15  ragm.  of  urea  nitrogen  are 
found  in  100  c.c.  of  blood.  In  early  nephritis  values  of  from  12-30  are 
observed  and  in  severe  nephritis,  values  from  30  up  to  the  300  seen  in 
some  cases  of  uremia. 

In  normal  blood  50  per  cent  of  the  non-protein  nitrogen  is  in  the 
form  of  urea.  In  uremia  the  percentage  may  increase  to  75  or  over. 

4.  Determination  of  Preformed  Creatinine. — Principle. — A  portion 
of  the  blood  filtrate  is  treated  with  alkaline  picrate  solution  and  the 
color  developed  compared  with  that  of  a  standard  in  a  colorimeter. 

Procedure. — Transfer  25  (or  50)  c.c.  of  a  saturated  solution  of  purified  picric 
acid1  to  a  small,  clean  flask,  add  5  (or  10)  c.c.  of  10  per  cent  sodium  hydroxide, 
and  mix.  Transfer  10  c.c.  of  blood  filtrate  to  a  small  flask  or  to  a  test  tube, 
transfer  5  c.c.  of  the  standard  creatinine  solution  described  below  to  another 
flask,  and  dilute  the  standard  to  20  c.c.  Then  add  5  c.c.  of  the  freshly  prepared 
alkaline  picrate  solution  to  the  blood  filtrate,  and  10  c.c.  to  the  diluted  creatinine 
solution.  Let  stand  for  8  to  10  minutes  and  make  the  color  comparison  in  the 
usual  manner,  never  omitting  first  to  ascertain  that  the  two  fields  of  the  colori- 
meter are  equal  when  both  cups  contain  the  standard  creatinine  picrate  solution. 
The  color  comparison  should  be  completed  within  15  minutes  from  the  time  the 
alkaline  picrate  was  added ;  it  is,  therefore,  never  advisable  to  work  with  more 
than  three  to  five  blood  filtrates  at  a  time.  tS 

When  the  amount  of  blood  nitrate  available  for  the  creatinine  "determination  is 
too  small  to  permit  repetition,  it  is  of  course  advantageous  or  necessary  to  start 
with  more  than  one  standard.  If  a  high  creatinine  should  be  encountered  unex- 
pectedly without  several  standards  ready,  the  determination  can  be  saved  by 
diluting  the  unknown  with  an  appropriate  amount  of  the  alkaline  picrate  solution — • 
using  for  such  dilution  a  picrate  solution  first  diluted  with  two  volumes  of  water — 
so  as  to  preserve  equality  between  the  standard  and  the  unknown  in  relation  to 
the  concentration  of  picric  acid  and  sodium  hydroxide. 

One  standard  creatinine  solution,  suitable  both  for  creatin  and  for  creatinine 
determinations  in  blood,  can  be  made  as  follows:  Transfer  to  a  liter  flask  6  c.c. 
of  the  standard  creatinine  solution  used  for  urine  analysis  (which  contains  6  mg.  of 
creatinine) ;  add  10  c.c.  of  normal  hydrochloric  acid,  dilute  to  the  mark  with  water, 
and  mix.  Transfer  to  a  bottle  and  add  four  or  five  drops  of  toluene  or  xylene. 
Five  c.c.  of  this  solution  contain  0.03  mg.  of  creatinine  and  this  amount  plus  15  c.c. 
of  water  represents  the  standard  needed  for  the  vast  majority  of  human  bloods,  for 
it  covers  the  range  of  i  to  2  mg.  per  100  c.c.  In  the  case  of  unusual  bloods  repre- 
senting retention  of  creatinine  take  10  c.c.  of  the  standard  plus  10  c.c.  of  water, 
which  covers  the  range  of  2  to  4  mg.  of  creatinine  per  100  c.c.  of  blood;  or  15  c.c.  of 
the  standard  plus  5  c.c.  of  water  by  which  4  to  6  mg.  can  be  estimated.  By  taking 
the  full  20  c.c.  volume  from  the  standard  solution  at  least  8  mg.  can  be  estimated; 
but  when  working  with  such  blood  it  is  well  to  consider  whether  it  may  not  be  more 

1  Picric  acid  may  be  purified  as  indicated  in  the  last  section  of  this  book. 


BLOOD    ANALYSIS  281 

advantageous  to  substitute  5  c.c.  of  blood  filtrate  plus  5  c.c.  of  water  for  the  usual 
10  c.c.  of  blood  filtrate. 

Calculation. — The  reading  of  the  standard  in  mm.  (usually  20)  multiplied 
by  1.5,  3,  4-5>  or  6  (according  to  how  much  of  the  standard  solution  was  taken), 
and  divided  by  the  reading  of  the  unknown,  in  mm.,  gives  the  amount  of  creat- 
inine  in  mg.  per  100  c.c.  of  blood.  In  connection  with  this  calculation  it  is  to  be 
noted  that  the  standard  is  made  up  to  twice  the  volume  of  the  unknown,  so  that 
each  5  c.c.  of  the  standard  creatinine  solution,  while  containing  0.03  mg.,  corre- 
sponds to  0.015  mg.  in  the  blood  filtrate. 

Interpretation. — Normally  creatinine  is  found  in  the  blood  to  the 
extent  of  1-2  mgs.  per  100  c.c.  In  early  nephritis  values  of  from  2-4 
mgs.  are  noted,  and  in  severe  nephritis  4-35  mg.  Creatinine  is  more 
readily  excreted  by  the  kidneys  than  urea  or  uric  acid,  and  any  in- 
crease of  creatinine  to  4  or  5  mgs.  or  over  per  100  c.c.  of  blood  indicates 
a  marked  impairment  of  kidney  function  and  a  probable  fatal  termi- 
nation within  a  relatively  short  time. 

« 

5.  Determination  of  Creatine  Plus  Creatinine. — Principle. — The  creatine  of 
the  blood  filtrate  is  transformed  to  creatinine  by  heating  with  dilute  HC1  in  an 
autoclave.     The   creatinine   preformed   and  from   creatine   are  then  determined 
together  by  treating  with  alkaline  picrate  as  under  preformed  creatinine. 

PrtfCtfdwre.-r-Transfer  5  c.c.  of  blood  filtrate  to  a  test  tube  graduated  at  25  c.c. 
These  test  tubes  are  also  used  for  urea  and  for  sugar  determinations.  Add  i  c.c. 
of  normal  hydrochloric  acid.  Cover  the  mouth  of  the  test  tube  with  tin-foil  and 
heat  in  the  autoclave  to  i3o°C.  for  20  minutes  or,  as  for  the  urea  hydrolysis,  to  i55°C 
for  10  minutes.  Cool.  Add  5  c.c.  of  the  alkaline  picrate  solution  and  let  stand 
for  8  to  10  minutes,  then  dilute  to  25  c.c.  The  standard  solution  required  is  10  c.c. 
of  creatinine  solution  in  a  50  c.c.  volumetric  flask.  Add  2  c.c.  of  normal  acid  and 
10  c.c.  of  the  alkaline  picrate  solution  and  after  10  minutes  standing  dilute  to  50  c.c. 
The  preparation  of  the  standard  must  of  course  have  been  made  first  so  that  it  is 
ready  for  use  when  the  unknown  is  ready  for  the  color  comparison.  The  height  of 
the  standard,  usually  20  mm.,  divided  by  the  reading  of  the  unknown  and  multi- 
plied by  6  gives  the  "total  creatinine"  in  mg.  100  c.c.  blood. 

In  the  case  of  uremic-  bloods  containing  large  amounts  of  creatinine  i,  2,  or 
3  c.c.  of  blood  filtrate,  plus  water  enough  to  make  approximately  5  c.c.,  are  sub- 
stitutes for  5  c.c.  of  the  undiluted  filtrate. 

Interpretation. — Total  creatinine  as  determined  by  this  method  gives  values  of 
about  5-6  mg.  per  100  c.c.  for  normal  blood.*  High  values  for  creatine  have  been 
obtained  in  severe  nephritis. 

6.  Determination   of   Uric  Acid.1 — Principle. — Uric  acid  is  pre- 
cipitated as  silver  urate  directly  from  the  blood  nitrate.     The  uric  acid 

1  The  following  solutions  are  required  for  uric  acid  determinations: — 
i.  The  standard  uric  acid  sulphite  solution,  prepared  as  follows:  In  a  500  c.c.  flask 
dissolve  exactly  i  gm.  of  uric  acid  in  150  c.c.  of  water  by  the  help  of  0.5  g.  lithium  carbonate. 
Dilute  to  500  c.c.  and  mix.  Transfer  50  c.c.  to  a  liter  flask;  add  500  c.c.  of  20  per  cent 
sodium  sulphite  solution;  dilute  to  volume  and  mix.  Transfer  to  small  bottles  (capacity 
200  c.c.)  and  stopper  tightly.  This  standard  uric  acid  solution  keeps  almost  indefinitely 


282  PHYSIOLOGICAL   CHEMISTRY 

is  set  free  by  means  of  chloride  solution  and  determined  colorimetric- 
ally  after  addition  of  phosphotungstic  acid  which  gives  a  blue  solution. 

Procedure.^l-To  10  c.c.  of  blood  filtrate  in  each  of  two  centrifuge  tubes  add 
2  c.c.  of  a  5  per  cent  solution  of  silver  lactate  in  5  per  cent  lactic  acid,  and  stir 
with  a  very  fine  glass  rod.  Centrifuge ;  add  a  drop  of  silver  lactate  to  the  super- 
natant solution,  which  should  be  almost  perfectly  clear  and  should  not  become 
turbid  when  the  last  drop  of  silver  solution  is  added.  Remove  the  supernatant 
liquid  by  decantation  as  completely  as  possible.  Add  to  each  tube  i  c.c.  of  a 
solution  of  10  per  cent  sodium  chloride  in  o.i  normal  hydrochloric  acid  and  stir 
thoroughly  with  the  glass  rod.  Then  add  5  to  6  c.c.  of  water,  stir  again,  and 
centrifuge  once  more.  By  this  chloride  treatment  the  uric  acid  is  set  free  from 
the  precipitate.  Transfer  the  two  supernatant  liquids  by  decantation  to  a  25  c.c. 
volumetric  flask.  Add  i  c.c.  of  a  10  per  cent  solution  of  sodium  sulphite,  0.5 
c.c.  of  a  5  per  cent  solution  of  sodium  cyanide,  and  3  c.c.  of  a  20  per  cent  solution 
of  sodium  carbonate.  Prepare  simultaneously  two  standard  uric  acid  solutions 
as  follows : 

Transfer  to  one  50  c.c.  volumetric  flask  i  c.c.  and  to  another  50  c.c.  flask 
2  c.c.  of  the  standard  uric  acid  sulphite  solution  described  above.  To  the  first 
flask  add  also  i  c.c.  of  10  per  cent  sodium  sulphite  solution.  Then  add  to  each 
flask  4  c.c.  of  the  acidified  sodium  chloride  solution,  i  c.c.  of  the  sodium  cyanide 
solution,  and  6  c.c.  of  the  sodium  carbonate  solution.  Dilute  with  water  to 
about  45  c.c.  When  the  two  standard  solutions  and  the  unknown  have  been 
prepared  as  described  they  are  ready  for  the  addition  of  the  uric  acid  reagent. 
Add  0.5  c.c.  of  this  reagent  to  the  unknown  and  i  c.c.  to  each  of  the  standards, 
and  mix.  Let  stand  for  10  minutes,  fill  to  the  mark  with  water,  mix,  and  make 
the  color  comparison.) 

Calculation. — In  connection  with  the  calculation  it  is  to  be  noted  (a)  that 
the  blood  filtrate  taken  corresponds  to  2  c.c.  of  blood,  (b)  that  the  standard  is 
diluted  to  twice  the  volume  of  the  unknown,  and  (c)  that  the  standard  used  con- 
tains o.i  or  0.2  mg.  of  uric  acid.  The  blood  filtrate  from  blood  containing 
2.5  mg.  of  uric  acid  will  be  just  equal  in  color  to  the  weaker  standard.  Twenty 
times  2.5  divided  by  the  reading  of  the  unknown  gives,  therefore,  the  uric  acid 
content  of  the  blood  when  the  weaker  standard  is  set  at  20  mm. 

The  uric  acid  may  sink  to  as  low  as  i  mg.  of  uric  acid  per  100  c.c.  of  blood. 
It  seems  hardly  worth  while  to  prepare  a  third  and  weaker  standard  regularly  in 
order  to  provide  for  such  low  acid  values. 

A  standard  corresponding  to  the  color  obtained  from  1.25  mg.  of  uric  acid  per 
100  c.c.  of  blood  can  be  prepared  within  a  couple  of  minutes  as  follows :  Transfer 

in  unopened  bottles,  because  the  sulphite  prevents  the  spontaneous  oxidation  of  the  uric 
acid.  In  used  bottles  the  standard  usually  remains  good  for  2-3  months. 

2.  A  10  per  cent  sodium  sulphite  solution. 

3.  A  5  per  cent  sodium  cyanide  solution,  to  be  added  from  a  burette. 

4.  A  10  per  cent  solution  of  sodium  chloride  in  o.i  normal  hydrochloric  acid. 

5.  A  uric  acid  reagent  prepared  according  to  Folin  and  Denis.     This  may  be  made  as 
follows:  Introduce  into  a  flask 

750  c.c.  of  water, 
-'*  100  g.  of  sodium  tungstate, 

80  c.c.  of  phosphoric  acid  (85  per  cent  H3PO4). 

Partly  close  the  mouth  of  the  flask  with  a  funnel  and  small  watch  glass  and  boil  gently  for 
two  hours.  Dilute  to  a  liter.  A  still  stronger  reagent  is  obtained  by  heating  for  24  hours, 
instead  of  2  hours;  but  the  advantage  gained,  about  20  per  cent,  is  not  needed. 

6.  A  solution  of'5  per  cent  silver  lactate  in  5  per  cent  lactic  acid. 


BLOOD    ANALYSIS 


283 


i  c.c.  of  10  per  cent  sulphite  solution;  3  c.c.  of  20  per  cent  sodium  carbonate,  2  c.c. 
of  the  acidified  sodium  chloride,  0.5  c.c.  of  the  sodium  cyanide  solution,  and  25 
c.c.  of  the  weaker  one  of  the  two  regular  standard  solutions  already  on  hand. 
Dilute  to  50  c.c.  and  mix.  Or,  simply  add  5  c.c.  of  20  per  cent  sodium  carbonate 
to  25  c.c.  of  the  regular  weaker  standard,  and  dilute  to  50  c.c. 

If  a  low  uric  acid  value  is  expected,  an  alternate  procedure  is  to  dilute  the  un- 
known to  a  final  volume  of  10  c.c.  with  corresponding  reduction  in  the  amount 
.of  the  reagents  used. 

Special  attention  should  perhaps  be  called  to  one  small 
yet  essential  variation  in  the  process  for  developing  the 
blue  uric  acid  color,  a  variation  made  necessary  by  the 
use  of  sodium  sulphite.  The  uric  acid  reagent  must 
invariably  be  added  after,  and  not  before,  the  addition  of 
the  sodium  carbonate,  because  in  acid  solution  the  sulphite 
will  itself  give  a  blue  color  with  phosphotungstic  acid. 

25  cc. 


Interpretation.  —  Normal  human  blood  usually 
contains  from  2-3  mg.  of  uric  acid  per  100  c.c. 
In  early  interstitial  nephritis  values  of  from  3-10 
mg.  are  noted.  Uric  acid  increases  in  the  bkfod 
in  this  condition  sooner  than  urea  or  creatinine, 
probably  because  it  is  less  soluble  and  less  readily 
excreted  by  the  kidneys.  The  determination  of 
uric  acid  is,  therefore,  of  especial  value  in  early 
nephritis.  In  severe  nephritis  values  up  to  25 
mg.  may  be  obtained. 

In  gout  high  uric  acid  values  (4-10  mg.)  are 
usually  found.  Determination  of  uric  acid,  there- 
fore, is  of  value  in  the  diagnosis  of  gouty  arthritis 
prior  to  the  stage  of  tophi  formation.  It  must 
be  borne  in  mind,  however,  that  uric  acid  is 
similarly  increased  in  early  nephritis  and  that 
many  cases  of  gout  showing  high  uric  acid  values 
also  show  defective  kidney  function  by  other 
tests.  The  same  difficulty  is  met  with  in  con-  (Folhnd  Wu: 
sidering  the  high  values  (2-8  mg.)  obtained  in  Biol.  Chem.,  March, 
other  arthritis  conditions,  usually  associated  with 
increases  in  urea  also.  The  existence  of  nephritis  in  such  cases  has 
not  been  entirely  excluded  and  many  typical  cases  of  arthritis  show 
values  below  3  mg.1  Salicylates  and  atophan  tend  to  reduce  the  uric 
acid  content  of  the  blood. 

7.  Determination  of  Sugar.  —  Principle.  —  The  protein-free  blood 
nitrate  is  heated  with  alkaline  copper  solution,  using  a  special  tube 
to  prevent  reoxidation.  The  cuprous  oxide  formed  is  treated  with  a 

1  See  Myers:  "Practical  Chemical  Analysis  of  Blood,"  St.  Louis,  1921. 


t—  8mm. 


4cc. 

(Not  Marked) 


FIG-  89.—  FOLIN-WU 


284  PHYSIOLOGICAL   CHEMISTRY 

molybdate  phosphate  solution,  a  blue  color  being  obtained  which  is 
compared  with  that  of  a  standard. 

Procedure. — Transfer  2  c.c.  of  the  tungstic  acid  blood  filtrate  to  a  blood 
sugar  test  tube  of  the  type  illustrated  in  Fig.  89 1  and  to  two  other  similar  test 
tubes  (graduated  at  25  c.c.)  add  2  c.c.  of  standard  sugar  solution  containing 
respectively  0.2  and  0.4  mg.  of  glucose.2  To  each  tube  add  2  c.c.  of  the  alkaline 
copper  solution.3 

The  surface  of  the  mixtures  must  now  have  reached  the  constricted  part  of 
the  tube.  If  the  bulb  of  the  tube  is  too  large  for  the  volume  (4  c.c.)  a  little,  but 
not  more  than  0.5  c.c.  of  a  diluted  (i  :i)  alkaline  copper  solution  may  be  added. 
If  this  does  not  suffice  to  bring  the  contents  to  the  narrow  part,  the  tube  should 
be  discarded.  Test  tubes  having  so  small  a  capacity  that  4  c.c.  fills  them  above 
the  neck  should  also  be  discarded.  Transfer  the  tubes  to  a  boiling  water  bath 
and  heat  for  6  minutes.  Then  transfer  them  to  a  cold  water  bath  and  let  cool 
without  shaking  for  2  or  3  minutes.  Add  to  each  test  tube  2  c.c.  of  the  molyb- 
date phosphate  solution.4  The  cuprous  oxide  dissolves  rather  slowly  if  the 
amount  is  large  but  the  whole,  up  to  the  amount  given  by  0.8  mg.  of  glucose,  dis- 
solves usually  within  2  minutes.  When  the  cuprous  oxide  is  dissolved,  dilute 
the  resulting  blue  solutions  to  the  25  c.c.  mark,  insert  a  rubber  stopper,  and  mix. 
It  is  essential  that  adequate  attention  be  given  to  this  mixing  because  the  greater 
part  of  the  blue  color  is  formed  in  the  bulb  of  the  tube.  Compare  hi  a  colori- 
meter using  the  standard  which  most  nearly  matches  the  unknown. 

The  two  standards  given  representing  0.2  and  0.4  mg.  of  glucose  are  adequate 
for  practically  all  cases.  They  cover  the  range  from  about  70  to  nearly  400  mg. 
of  glucose  per  100  c.c.  of  blood.  )/ 

It  will  be  noted  that  in  the  process  described  cooling  of  the  alkaline  cuprous 
oxide  suspension  before  adding  the  phosphate  molybdate  solution  is  suggested. 

1  These  test  tubes,  with  or  without  graduation,  may  be  obtained  from  Emil  Greiner, 
New  York. 

2  Standard  Sugar  Solutions. — Three  standard  sugar  solutions  should  be  on  hand:  (i) 
a  stock  solution,  i  per  cent  glucose  or  invert  sugar,  preserved  with  xylene  or  toluene; 
(2)  a  solution  containing  i  mg.  of  sugar  per  10  c.c.  (  5  c.c.  of  the  stock  solution  diluted 
to '500  c.c.);  (3)  a  solution  containing  2  mg.  of  sugar  per  10  c.c.  (  5  c.c.  of  the  stock  solution 
diluted  to  250  c.c.).     The  invert  sugar  solution  has  the  advantage  that  it  can  be  easily 
prepared  from  cane  sugar,  which  is  pure.     When  good  quality  glucose  is  available,  it  is, 
of  course,  the  one  to  use.     The  diluted  solutions  should  be  preserved  with  a  little  added 
toluene  or  xylene;  it  is  probably  better  not  to  depend  on  such  diluted  solutions  to  keep  for 
more  than  a  month,  but  the  stock  solution  should  keep  indefinitely. 

3  Alkaline  Copper  Solution. — Dissolve  40  gm.  of  pure  anhydrous  sodium  carbonate 
in  about  400  c.c.  of  water  and  transfer  to  a  liter  flask.     Add  7.5  gm.  of  tartaric  acid,  and 
when  the  latter  has  dissolved  add  4.5  gm.  of  crystallized  copper  sulfate.     Mix  and  make 
up  to  a  volume  of  i  liter.     If  the  chemicals  used  are  not  pure  a  sediment  of  cuprous  oxide 
may  form  in  the  course  of  i  or  2  weeks.     If  this  should  happen,  remove  the  clear  super- 
natant reagent  with  a  siphon,  or  filter  through  a  good  quality  filter  paper.     The  reagent 
seems  to  keep  indefinitely.     To  test  for  the  absence  of  cuprous  copper  in  the  solution, 
transfer  2  c.c.  to  a  test  tube  and  add  2  c.c.  of  the  molybdate  phosphate  solution;  the  deep 
blue  color  of  the  copper  should  almost  completely  vanish.     In  order  to  forestall  improper 
use  of  this  reagent  attention  should  be  called  to  the  fact  that  it  contains  extremely  little 
alkali,  2  c.c.  by  titration  (using  the  fading  of  the  blue  copper  tartrate  color  as  indicator), 

aequ    ;«i      .n  v  bout  1.4  c.c.  of  normal  acid. 

4  Transfer  -lo  a  liter  beaker  35  gm.  of  molybdic  acid  and  5  gm.  of  sodium  tungstate. 
Add  200  c.c.  of  10  per  cent  sodium  hydroxide  and  200  c.c.  of  water.     Boil  vigorously  for 
20  to  40  minutes  so  as  to  remove  nearly  the  whole  of  the  ammonia  present  in  the  molybdic 
acid.     (The  molybdic  acid  which  may  be  obtained  from  the  Primos  Company,  Primos, 
Pa.,  contains  considerable  ammonia.)     Cool,  dilute  to  about  350  c.c.,  and  add  125  c.c. 
of  concentrated  (85  per  cent)  phosphoric  acid.     Dilute  to  500  c.c. 


BLOOD   ANALYSIS  285 

This  cooling  is  not  essential  and,  in  case  of  one  or  two  determinations  only,  may 
be  omitted.  In  a  large  series  of  determinations  it  is  probably  best  to  use  it.  The 
important  point  is  that  the  standard  and  the  unknowns  should  not  only  be  heated 
the  same  length  of  time  but  should  also  have  substantially  the  same  temperature 
when  the  acid  reagent  is  added.  The  maximum  color  develops  faster  in  hot  solu- 
tions; but  if  a  reasonable  uniformity  of  condition  is  maintained  it  makes  no  differ- 
ence whether  the  color  comparison  is  made  at  the  end  of  5  minutes  or  at  the  end  of 
i  hour. 

Reading  of  Standard      mg.  of  glucose  in  standard 

Calculations.—  -X  -  -  =  Grams 

Reading  of  Unknown  2 

of  glucose  per  100  c.c.  of  blood. 

Interpretation.— ^Normal  blood  contains  from  0.08  to  0.12  per  cent, 
of  glucose.  In  mild  diabetes  values  of  from  0.14  to  0.30  are  obtained, 
and  in  severe  diabetes  values  up  to  1.2  per  cent.  Hyperglycemia  is 
found  also  in  nephritis  and  hyper  thy  roidism.  Hypoglycemia  has  been 
noted  in  hypo  thy  roidism,  Addison's  disease,  muscular  dystrophy, 
etc.  Normally  sugar  begins  to  appear  in  the  urine  when  the  blood 
concentration  reaches  0.15  to  0.18  per  cent. 

The  concentration  of  sugar  in  the  corpuscles  is  usually  a  little  lower 
than  in  the  plasma  and  more  variable.  Plasma  determinations  may, 
therefore,  possess  some  advantage  over  whole  blood  determinations. 1 
For  sugar  tolerance  test  see  page  290. 

8.  Determination  of  Chlorides.2 — Principle. — The  chlorides  are 
precipitated  from  the  blood  filtrate  by  means  of  silver  nitrate  in  the 
presence  of  nitric  acid  and  the  excess  of  silver  titrated  with  standard 
sulphocyanate  solution,  using  ferric  ammonium  sulphate  as  an  indicator. 

Procedure. — Because  of  the  slight  variations  in  the  chloride  content  of  blood, 
dilution  in  preparation  of  protein-free  filtrates  should  be  made  very  carefully 
and  volumetric  flasks  may  be  preferred. 

Pipette  10  c.c.  of  the  protein-free  filtrate  into  a  porcelain  dish.  Add  with  a 
pipette  5  c.c.  of  the  standard  silver  nitrate  solution3  and  stir  thoroughly.  Add 

1  Wishart,  M.  B.:  Jour.  Biol.  Chem.,  44,  563,  1920. 

2Whitehorn,  J.  C.:  Jour,  Biol.  Chem.,  45,  449,  1921.  This  method  is  applicable  to 
plasma  and  whole  blood.  The  same  principle  was  used  by  Rieger:  /.  Lab.  Clin.  Med., 
6,  44,  1920-21.  Rappleye:  Jour.  Biol.  Chem.,  35,  509,  1918,  showed  that  the  Volhard 
method  could  be  applied  directly  to  plasma  without  prior  removal  of  protein.  Van  Slyke 
and  Donleavy:  Jour.  Biol.  Chem.  37,  551,  1919,  showed  that  the  iodometric  method  of 
McLean  and  Van  Slyke:  Jour.  Biol.  Chem.,  21,  361,  1915,  could  also  be  used  in  this  way. 
Austin  and  Van  Slyke:  Jour.  Biol.  Chem.,  41,  345,  1920,  used  the  picric  acid  precipitation 
in  the  case  of  whole  blood.  Myers  and  Short:  Jour.  Biol.  Chem.,  44,  47,  1920,  have  com- 
bined the  picric  acid  precipitation  of  protein  with  the  Volhard  titration  to  produce  a  con- 
venient and  satisfactory  method.  Wetmore;  Jour.  Biol.  Chem.,  45,  113,  1920,  uses  copper 
hydroxide  precipitation  and  the  Volhard  titration. 

3  Preparation  of  Reagents. — Dissolve  4.791  gm.  of  C.P.  silver  nitrate  in  distilled  water. 
Transfer  this  solution  to  a  liter  volumetric  flask  and  make  up  to  the  mark  with  distilled 
water.  Mix  thoroughly  and  preserve  in  a  brown  bottle,  i  c.c.  =  i  mg.  Cl.  (It  is  to  be 
noted  that  the  silver  nitrate  and  nitric  acid  are  not  added  to  the  protein-free  nitrate  simul- 
taneously. To  do  so  may  result  in  the  mechanical  enclosure  of  silver  nitrate  solution 
within  the  curds,  and  a  consequent  error  in  the  positive  direction.) 

Because  sulfocyanates  are  hygroscopic,  the  standard  solution  should  be  prepared 
volu metrically.  As  an  approximation  about  3  gm.  of  KCNS  or  2.5  gm.  of  NEUCNS  should 


286 


PHYSIOLOGICAL   CHEMISTRY 


about  5  c.c.  of  concentrated  nitric  acid  (sp.  gr.  1.42),  mix,  and  let  stand  for  5 
minutes,  to  permit  the  flocking  out  of  the  silver  chloride.  Then  add  with  a 
spatula  an  abundant  amount  of  powdered  ferric  ammonium  sulfate  (about  0.3  gm.) 
and  titrate  the  excess  of  silver  nitrate  with  the  standard  sulfocyanate  solution 
until  the  definite  salmon-red  (not  yellow)  color  of  the  ferric  sulfocyanate  persists 
in  spite  of  stirring  for  at  least  15  seconds. 

Calculation. — 5.00  (cc.AgNO3  used)  -  x(cc.KCNS  used)  =  mg.  of  Cl  per 
c.c.  of  blood  (or  plasma).  To  express  as  NaCl  multiply  Cl  value  by  1.65. 

Interpretation. — Whole  blood  normally  contains  from  0.45  to  0.50 
per  cent  of  chlorides  expressed  as  sodium  chloride,  and  the  plasma 
from  0.57  to  0.62  per  cent.  Higher  values  are  obtained  in  nephritis, 
and  this  determination  may  aid  in  deciding  whether  or  not  salt  should 
be  restricted  in  the  diet.  There  may  be  a  decrease  of  chloride  in 
diabetes  and  fevers  as  well  as  in  pneumonia  with  chloride  retention. 


FIG.  90. — ASPIRATION  APPARATUS  FOR  UREA  DETERMINATION. 

(Myers:  "Practical  Chemical  Analysis  of  the  Blood,"  C.  V.  Mosby  Co.,  St.  Louis, 
1921.  Myers  suggests  the  use  of  test  tubes  within  the  cylinders  as  illustrated  for  ease  in 
manipulation).  & 

METHODS   CONTINUED 

i.  Urea,— The  Urease  Method.— Van  Slyke  and  Cullen's1  Modification  of 
Marshall's  Method.2 

Principle.— See  Urease  Method,  Chapter  XXVII. 

Procedure. — Run  3  c.c.  of  fresh  blood  (carefully  measured  with  an  accurate 
pipette)  Into  a  100  c.c.  test-tube  containing  i  c.c.  of  a  3  per  cent  solution  of  potas- 
sium citrate  (to  prevent  clotting).  Add  0.5  c.c.  of  the  urease  solution3  and  2  or  3 
drops  of  caprylic  alcohol  (to  prevent  foaming).4  After  ten  minutes  add  15  c.c. 

be  dissolved  in  a  liter  of  water.  By  titration  under  the  conditions  specified  under  "Pro- 
cedure" and  by  proper  dilution  prepare  a  standard  such  that  5  c.c.  are  equivalent  to  5  c.c 
of  the  silver  nitrate  solution. 

The  solid  ferric  alum  is  used  rather  than  a  solution,  in  order  to  insure  a  very  high  con- 
centration in  the  mixture  to  be  titrated.  It  is  powdered  in  order  to  facilitate  its  solution. 

1  Van  Slyke  and  Cullen:  /.  Am.  Med.  Ass'n,  62,  1558,  1914. 

2  Marshall:  Jour.  Biol.  Chem.,  15,  487,  1913. 

3  The  enzyme  solution  is  prepared  as  described  under  "Reagents  and  Solutions,"  p.  646. 

4  Lee  (St.  Luke's  Hosp.  Med.  and  Surg.  Rep.,  4,  1917)  suggests  the  use  of  a  mixture  con- 
taining 70  per  cent  phenyl  ether  and  30  per  cent  amyl  alcohol  as  a  substitute  for  caprylic 
alcohol,  while  Hammett  (Jour.  Biol.  Chem.,  33,  381,  1918)  uses  a  mixture  of  equal  parts 
of  amyl  alcohol,  toluene  and  ethyl  alcohol. 


BLOOD   ANALYSIS  287 

of  a  saturated  solution  of  potassium  carbonate,  and  drive  off  the  ammonia  by 
aspiration  into  another  tube  containing  15  c.c.  of  hundredth-normal  hydrochloric 
or  sulphuric  acid.  Titrate  the  excess  of  acid  with  hundredth-normal  sodium 
hydroxide  or  potassium  hydroxide,1  using  methyl  red  or  alizarin  as  indicator. 
The  aspiration  apparatus  of  Meyers  (see  Fig.  90)  may  be  used. 

Calculations. — Each  cubic  centimeter  of  acid  neutralized  by  the  ammonia 
during  aspiration  indicates  o.oi  gram  of  urea  per  100  c.c.  of  blood,  or  0.00467 
gram  of  urea  nitrogen  per  100  c.c.  of  blood.  In  case  the  blood  should  be  one  of 
the  rare  samples  containing  over  0.15  per  cent  of  urea,  all  the  acid  will  be  neu- 
tralized, and  it  will  be  necessary  to  repeat  the  determinations,  using  in  the  deter- 
mination only  i  c.c.  of  blood.  Fresh  blood  contains  so  little  ammonia  that  it 
may  be  disregarded.  For  further  discussion  of  the  urease  method  see  Chapter 
XXVII. 

2.  Sugar,  (a)  Benedict2  Modification  of  the  Method  of  Lewis 
and  Benedict.3 — Principle. — The  red  color  obtained  by  heating  a 
glucose  solution  with  picric  acid  and  sodium  carbonate  is  employed 
as  the  basis  of  the  colorimetric  determination.  The  blood  protein 
is  removed  by  precipitation  with  picric  acid. 

Procedure. — Two  c.c.  of  blood  are  aspirated  through  a  hypodermic  needle4 
and  a  piece  of  rubber  tubing  into  an  Ostwald  pipette,  a  little  powdered  potassium 
oxalate  in  the  tip  of  the  pipette  preventing  clotting.  The  blood  is  drawn  up  a 
little  above  the  mark  and  the  end  of  the  pipette  is  closed  with  the  finger.  After 
the  rubber  tubing  and  needle  are  disconnected,  the  blood  is  allowed  to  flow  back 
to  the  mark  and  is  discharged  at  once  into  a  25  c.c.  volumetric  flask,  or  into  a 
large  test-tube  graduated  at  12.5  c.c.  and  at  23  c.c.  The  pipette  is  twice  rinsed 
with  distilled  water,  these  washings  being  added  to  the  blood.  The  contents 
of  the  flask  are  shaken  to  insure  thorough  mixing  and  a  consequent  laking  or 
hemolysis  of  the  blood,  which  is  practically  complete  after  a  minute  or  two. 
A  solution  of  sodium  picrate  and  picric  acid6  is  added  to  the  25  c.c.  mark  (using 
a  few  drops  of  alcohol  to  dispel  foam  if  necessary)  and  the  mixture  thoroughly 
shaken.  After  a'  minute  or  two  (or  longer)  the  mixture  is  poured  upon  a  dry 
filter,  and  the  clear  filtrate  collected  in  a  dry  beaker.  Exactly  8  c.c.  of  the  filtrate 
are  measured  into  a  large  test-tube  bearing  graduations  at  the  12.5  c.c.  and  25  c.c. 
mark,  and  i  c.c.  of  20  per  cent  (anhydrous)  sodium  carbonate  solution  is  added. 
The  tube  is  plugged  with  cotton  and  immersed  in  boiling  water  for  10  minutes.6 
It  is  then  removed,  and  the  contents  are  cooled  under  running  water  and  diluted 

1  Rose  and  Coleman  (Biochem.  Bull.,  3,  411,  1914)  suggest  the  colorimetric  determina- 
tion of  the  ammonia.  . 

2  Benedict:  Jour.  Biol.  Chem.,  34,  203,  1918. 

3 Lewis  and  Benedict:  Jour.  Biol.  Chem.,  20,  61,  1915.  For  other  modifications  see 
Pearce:  Jour.  Biol.  Chem.,  22,  525,  1915,  and  Myers  &  Bailey:  Jour.  Biol.  Chem.,  24,  147, 
1916. 

4  It  may  be  more  convenient  to  draw  about  5  c.c.  of  blood  directly  into  a  test-tube 
containing  a  little  finely  powdered  potassium  oxalate  and  removing  2  c.c.  portions  of  this 
with  the  Ostwald  pipette. 

5  To  prepare  the  picrate-picric  acid  solution,  place  36  gm.  of  dry  powdered  picric  acid 
in  a  liter  flask  or  stoppered  cylinder,  add  500  c.c.  of  i  per  cent  sodium  hydroxide  solution, 
and  400  c.c.  of  hot  water.     Shake  occasionally  until  dissolved.     Cool  arid  dilute  to  i  liter. 

6  Longer  heating  up  to  half  an  hour  makes  no  change  in  the  color. 


288  PHYSIOLOGICAL   CHEMISTRY 

to  12.5  c.c.  or  to  25  c.c.  depending  on  the  depth  of  color.1  At  any  time  within 
a  hatf  an  hour  the  colored  solution  is  compared  in  a  colorimeter  with  a  suitable 
standard  solution,  the  standard  being  set  at  a  height  of  15  mm. 

The  standard  solution  may  be  simultaneously  prepared  from  pure  glucose 
by  treating  0.64  mg.  of  glucose  in  4  c.c.  of  water  with  4  c.c.  of  the  pier  ate -picric 
acid  solution  and  i  c.c.  of  the  carbonate,  and  heating  for  10  minutes  in  boiling 
water  and  then  diluting  to  12.5  c.c.  A  permanent  standard  solution  may  be 
prepared  from  picramic  acid  or  from  potassium  dichromate  as  mentioned  below.2 
The  potassium  dichromate  standard  does  not  match  the  unknown  with  absolute 
exactness,  but  can  be  employed  with  satisfactory  results  when  pure  picramic 
acid  is  not  obtainable. 

Calculation. — If  directions  are  followed  exactly  the  calculation  is  as  follows : 

Reading  of  standard 

Reading  of  unknown  +  IO  =  per  cent  °f  Sugar  m  **  Ongmal  blood' 
Where  the  final  dilution  of  the  unknown  is  made  to  25  c.c.  instead  of  12.5  c.c. 
the  final  figure  is,  of  course,  multiplied  by  two. 

(b)  Micro -method  of  Bang. — Principle. — Two  or  3  drops  of 
blood  are  transferred  to  a  small  weighed  piece  of  blotting  paper  and  the 
paper  again  weighed  to  determine  the  amount  of  blood.  The  paper  is 
then  treated  with  a  boiling  acidified  KC1  solution  which  coagulates  the 
protein  and  allows  the  sugar  to  diffuse  out.  The  sugar  solution  thus 
obtained  is  boiled  with  alkaline  cupric  chloride  solution.  The  amount 
of  cuprous  chloride  solution  formed  by  the  reducing  action  of  the 
sugar  is  determined  by  titration  with  standard  iodine  solution. 

Procedure. — Small  pieces  of  good  absorbent  paper,  about  16X28  mm.  in 
size,3  weighing  about  100  mg.  and  held  by  a  small  spring  clip,  are  used.  To  one 
of  these  previously  weighed4  transfer  2-3  drops  (about  120  mg.)  of  blood  obtained 
by  piercing  the  cleansed  ringer.  Weigh  again  immediately  and  determine  by 
subtraction  the  weight  of  blood  taken. 

1  Occasionally  the  final  filtrates  in  this  or  other  picric  acid  methods  develop  a  little 
turbidity  during  heating.     Unless  such  turbidity  is  fairly  marked  it  is  of  no  account. 
When  desired,  the  final  colored  solution  may  be  filtered  through  a  small  folded  filter  into 
the  colorimeter  cup. 

2  Permanent  Standard. — The    picramic  acid  standard  is  best  prepared  from  a  stock 
solution  containing  100  mg.  of  picramic  acid  and  200  mg.  of  sodium  carbonate  per  liter. 
One  hundred  twenty-six  c.c.  of  this  solution  are  treated  with  i  c.c.  of  the  20  per  cent 
sodium  carbonate  solution  and  15  c.c.  of  the  picrate-picric  acid  solution,  and  diluted  to 
300  c.c.  with  distilled  water.    This  solution  matches  exactly  the  color  obtained  by  treat- 
ing 0.64  mg.  of  glucose,  as  in  the  above  method  and  diluting  to  12.5  c.c.     A  satisfactory 
preparation   of   picramic  acid  may  be  obtained  from  the  J.  T.  Baker  Chemical  Co., 
Phillipsburg,  N.  J. 

The  standard  prepared  from  potassium  dichromate  contains  800  mg.  of  pure  potassium 
dichromate  in  a  liter  of  water. 

3  Suitable  pieces  of  paper,  weighed,  ready  for  use,  and  with  clip  attached,  may  be  ob- 
tained from  Warmbrunn  and  QuiUtz,  Berlin.     A  suitable  paper  may  also  be  obtained  from 
Griffin  and  Sons,  London,  or  Grave  of  Stockholm.     Unless  specially  prepared,  the  paper 
should  be  repeatedly  washed  with  large  volumes  of  hot  water  acidified  with  acetic  acid  to 
remove  impurities. 

4  The  weighing  is  preferably  made  on  a  special  torsion  micro-balance  which,  as  well  as 
the  other  apparatus  used  in  this  method,  may  be  obtained  from  either  of  the  firms  mentioned 
in    Note   3,    above.     The    weighing    must    be    made    in    a  few  seconds  a*nd  with  an 
accuracy  of  about  i  mg. 


BLOOD   ANALYSIS  289 

Coagulation  of  Blood  Protein. — Transfer  the  piece  of  paper  to  a  test-tube  and 
add  6.5  c.c.  of  boiling  acid-potassium  chloride  solution1  and  let  stand  half  an  hour. 
The  clear  solution  containing  the  sugar  is  poured  into  a  50  c.c.  Jena  flask  the 
flange  of  which  has  been  removed.  Wash  the  paper  and  tube  again  with  6.5  c.c. 
of  hot  salt  solution  and  transfer  washings  to  the  flask.  Cool. 

Reduction  of  Cupric  Chloride. — Attach  to  the  mouth  of  the  flask  a  piece  of 
tight-fitting  rubber  tubing  about  2  inches  long  (see  Fig.  91),  provided  with  a 
clamp  which  permits  of  shutting  off  the  contents  of  the  flask  from  the  outside  air. 
Now  add  to  the  flask  i  c.c.  of  the  cupric  chloride  solution.2  Heat  so  that  the 
solution  is  brought  to  a  boil  in  one  minute  and  30  seconds  (an  error  of  five  seconds 
may  be  disregarded).  Allow  to  boil  for  exactly  two  minutes;  at  the  end  of  this 
time  tighten  the  clamp  over  the  mouth  of  the  flask.  At  the 
same  time  remove  from  the  flame  and  cool  at  once  under  the 
tap  for  about  a  minute. 

Titration  of  Cuprous  Chloride  Formed. — The  titration  is 
made  with  N/2OO  iodine  solution3  run  in  from  a  very  accurate 
burette  (preferably  a  2  c.c.  burette  graduated  in  1/50  c.c.). 
Two  or  3  drops  of  starch  solution  (preferably  soluble  starch4) 
are  added  as  an  indicator.  During  the  titration  air  must  be 
excluded  to  prevent  re-oxidation.  This  is  done  by  running  a 
slow  stream  of  carbon  dioxide  from  a  generating  bottle  through 
a  small  tube  which  extends  nearly  to  the  bottom  of  the  flask. 
The  titration  should  be  carried  out  against  a  white  background  FIG.  91. — 

and  the  end  point  taken  when  the  blue  color  persists  for  20-30 
seconds. 

Calculation. — The  copper  and  other  solutions  used  in  the  test  bind  about 
o.i  2  c.c.  of  the  iodine  solution.  This  amount  must  hence  be  subtracted  from 
the  reading.  The  corrected  reading  is  then  divided  by  4  to  obtain  the  num- 
ber of  milligrams  of  glucose  in  the  sample. 

.  Example. — If  0.68  c.c.  of  N/2OO  I  solution  were  required,  —  -  =  0.14 

mg.  glucose  in  the  amount  of  blood  used.    If  140  mg.  of  blood  were  taken  for 

analysis  the  per  cent  of  glucose  in  the  blood  would  be  —     -  X  0.14  mg.  =  o.i  per 
cent  glucose. 

The  results  obtained  by  this  method  are  a  little  higher  than  those  obtained 
by  other  reliable  methods  due  to  the  presence  of  certain  I -binding  substances  in 
blood.  As  these  appear  to  be  nearly  constant  in  amount  a  correction  may  be 
applied.  To  obtain  true  values  for  glucose  of  the  blood  therefore  subtract 
0.015  per  cent  from  the  value  obtained  as  above,  o.i  pe*r  cent  —  0.015  per  cent 
=  0.085  per  cent  glucose. 

1  Consisting  of  1360  c.c.  of  saturated  KC1  to  which  is  added  640  .c.c.  of  water  and  1.5 
c.c.  of  25  per  cent  HCL. 

i  2  Copper  solution.  Introduce  into  a  1000  c.c.  flask  700  c.c.  of  boiled  and  cooled  water. 
Warm  to  about  3o°C.  and  add  160  grams  of  pure  potassium  bicarbonate  in  powder  form. 
When  dissolved  add  66  grams  of  pure  KC1.  Cool  and  then  add  100  grams  potassium  car- 
bonate. Finally  add  100  c.c.  of  4.4  per  cent  solution  of  pure  crystalline  copper  sulphate. 
Let  stand  a  short  time,  then  make  to  mark  with  boiled  water.  Allow  to  stand  a  day  or  so 
before  using. 

3  N/2oo  I  solution,  made  fresh  each  day.     Dilute  N/io  I  solution  20  times,  or  make 
as  follows:    Introduce  into  a  100  c.c.  flask  2  grams  KI,  1-2  c.c.  of  2  per  cent  KIOj  solution 
and  5  c.c.  of  N/io  HCL     Make  to  mark  with  boiled  and  cooled  distilled  water. 

4  A  i  per  cent  solution  of  Kahlbaum's  soluble  starch  in  a  saturated  KC1  solution. 

19 


290 


PHYSIOLOGICAL   CHEMISTRY 


To  secure  accurate  results  the  method  of  Bang  must  be  rigidly  con- 
trolled, all  new  solutions  and  absorbent  papers  being  checked  up 
against  pure  0.2  per  cent  glucose  solutions.  Taylor  and  Hulton1 
also  suggest  the  following  precautions.  A  blank  check  must  be  made 
on  the  reagents  each  day  an  estimation  is  made.  0.10-0.15  gram  of 
blood  should  be  taken  and  must  spread  smoothly  on  the  paper.  The 
proteins  are  best  coagulated  by  heating  of  the  blood-impregnated 
papers  in  the  hot  air  oven  at  100°  (as  recommended  by  Gardner  and 
McLean)2  for  five  minutes  with  corks  of  flasks  inverted.  The  solu- 
tion should  be  boiled  four  minutes  for  complete  reduction.  The 
iodine  solution  must  be  fresh  each  day  and  checked  each  day.  Deter- 
minations should  be  made  in  triplicate.  Results  cannot  be  depended 
upon  to  be  more  accurate  than  to  0.005  gram  glucose  in  100  c.c.  blood. 
Other  authors  have  recommended  that  an  hour  instead  of  half  an  hour 
be  allowed  for  the  diffusion  of  the  blood  sugar,  the  fluid  being  brought 
to  the  boiling-point  twice  during  this  period  or  kept  in  a  bath  at  40°  C. 


BLOOD 

SUGAR 

PER 
CENT 

0.24 


0.22 


0.20 


0.18 


0.16 


0.14 


0.12 


Q.1Q 


Q.Q8 


lai  hr. 


2nd  hr, 


8rd  hr 


NORMAL 


—     HVPERTHYRO I  0  ISM  — AODISON's  DISEASE 

FIG.  92. — SUGAR  TOLERANCE  CURVES. 
(Myers:  "Practical  Chemical  Analysis  of  the  Blood,"  1921). 


(c)  Carbohydrate  Tolerance  Test  (Killian).1— Principle. — Blood 
sugar  is  determined  at  hourly  periods  following  the  ingestion  of  1.75  gm. 
of  glucose  per  kilogram  of  body  weight.  Urinary  sugar  for  the  24  hour 
period  following  the  ingestion  of  the  glucose  is  also  determined. 

Baylor  and  Hulton:  Jour.  BioL  Chhm.,  22,  63,  1915. 
2 Gardner  and  McLean:  Bicchem,J.,  8,  391,  1914. 
'Killian:  Proc.  Sor.  Exper.  BioL  and  Med.,  17,  91,  1920. 


BLOOD   ANALYSIS  2QI 

Procedure. — Give  the  patient,  the  first  thing  in  the  morning,  a  standard 
breakfast  consisting  of  two  slices  of  bread,  one  egg  in  any  form  and  one  cup  of 
water.  Two  hours  after  this  breakfast  have  the  patient  empty  the  bladder  and 
then  drink  200  c.c.  of  water.  One  hour  later  collect  a  specimen  of  urine  and 
one  of  blood  to  serve  as  controls.  Then  give  the  patient  1.75  gm.  of  glucose  per 
kilo  of  body  weight.  The  glucose  is  given  in  50  per  cent  solutions.1  Collect 
3  or  4  specimens  of  blood  at  hourly  intervals  and  analyze  for  sugar.  Following 
the  taking  of  glucose  collect  a  24  hour  specimen  of  urine  and  determine  its  sugar 
content. 

Interpretation. — In  normal  individuals  blood  sugar  rises  from  the 
normal  value  of  about  o.i  per  cent  to  about  0.15  per  cent  at  the  end  of 
the  first  hour  and  returns  to  normal  by  the  end  of  the  second  hourly 
period.  In  pathological  conditions  the  curve  does  not  follow  the  normal 
course.  Hyper  thyroidism,  diabetes,  and  nephritis  show  much  greater 
values,  depending  on  the  severity  of  the  disease,  and  the  return  to 
normal  is  delayed  for  3  hours  or  more.  The  high  sugar  concentration 
in  the  blood  during  the  test  may  or  may  not  JDC  accompanied  by  gly- 
curesis,  depending  upon  the  " threshold  point"  of  the  kidney.  In 
hypo-endocrine  conditions,  in  which  the  blood  sugar  is  low  ordinarily, 
the  curve  of  blood  sugar  during  a  tolerance  test  is  quite  "  flat."  Curves 
obtained  by  Killian  in  hyper  thyroiclism  and  Addison's  disease,  together 
with  the  curve  of  a  normal  case  are  shown  in  Fig.  92. 2  For  further 
discussion  of  the  application  of  sugar  tolerance  tests  consult  papers  by 
Hamman  and  Hirschman,3  Janney  and  Isaacson,  Bailey,  Williams 
and  Humphreys,  Allen,  Stillman  and  Fitz,  Killian  and  Macleod. 

3.  Determination  of  Cholesterol  (a)  (Method  of  Myers  and  War- 
dell).4 — Principle. — The  blood  is  dried  on  plaster  of  Paris  and  extracted 
with  chloroform.  Cholesterol  is  determined  colorimetrically  after 
adding  to  the  chloroform  extract  acetic  anhydride  and  sulphuric  acid. 

Procedure. — For  the  determination,  i  c.c.  of  blood,  plasma  or  serum  is 
pipetted  into  a  porcelain  crucible  or  small  beaker  containing  4  to  5  gm.  of  plaster 
of  Paris,  stirred,  and  dried,  preferably  in  a  drying  oven  for  an  hour.  It  is  now 
emptied  into  a  small  paper  extraction  shell  (4  cm.  long)  and  then  inserted  in 
a  short  glass  tube  (2.5  X  7  cm.)  in  the  bottom  and  sides  of  which  are  a  number 
of  small  holes.  This  is  now  attached  to  a  large  cork  on  a  small  reflux  condenser 
and  the  tube  and  cork  inserted  in  the  neck  of  a  150  c.c.  extraction  flask  containing 
about  20  to  25  c.c.  of  chloroform.  Extraction  is  continued  for  30  minutes  on  an 

Janney  and  Isaacson  (Arch.  Int.  Med.,  22,  160,  1918)  administer  the  glucose  in  40 
per  cent  solution  together  with  the  juice  of  one  lemon  and  without  the  preliminary  standard 
meal.  Two  blood  specimens  are  taken — just  before  giving  the  glucose  and  at  the  end  of 
two  hours. 

2 Myers:  Practical  Chemical  Analysis  of  Blood,  C.  V.  Mosby  Company,  1921. 

3 Hamman  and  Hirschman:  A rch.  Int.  Med.,  20,  761,  1917;  Bailey:  Arch.  Int.  Med., 
23,  455,  1919;  Williams  and  Humphreys:  Arch.  Med.  Int.,  23,  537,  546,  559,  1919;  Allen, 
Stillman,  and  Fitz:  Monograph  of  the  Rockefeller  Institute  for  Medical  Research^No. 
n,  1919;  Macleod:  Physiological  Reviews,  i,  208,  1921. 

4 Myers  and  Wardell:  Jour.  Biol.  Chem.,  36,  147,  1918. 


2Q2 


PHYSIOLOGICAL   CHEMISTRY 


electric  hot  plate,  the  chloroform  made  up  to  some  suitable  volume,  such  as 
20  c.c.,  filtered  if  necessary,  and  colorimetric  estimation  carried  out  as  follows : 
5  c.c.  of  the  chloroform  extract  are  pipetted  into  a  dry  test  tube,  and  2  c.c.  of 
acetic  anhydride  and  o.i  c.c.  of  concentrated  sulphuric  acid  (best  with  o.i  c.c. 
pipette)  are  added.  After  thorough  mixing,  the  solution  is  placed  in  the  dark 
for  exactly  10  minutes1  to  allow  the  color  to  develop,  and  then  compared  with  a 
standardized  0.005  per  cent  aqueous  solution  of  naphthol  green  B  in  a  Bock- 
Benedict  or  Kober  colorimeter.  If  the  Duboscq  colori- 
meter is  used,  it  is  necessary  that  the  cups  should  be 
remounted  in  plaster  of  Paris  instead  of  balsam. 

With  a  good  grade  of  acetic  anhydride,  it  has  been 
found  that  when  an  0.005  per  cent  solution  of  naphthol 
green  B  is  used  as  a  standard  and  set  a  15.5  mm.  on 
the  Duboscq  or  Kober  instrument,  0.4  mg.  of  cholesterol 
in  5  c.c.  of  chloroform  treated  with  2  c.c.  of  acetic  anhy- 
dride and  o.i  c.c.  of  concentrated  sulphuric  acid  will  read 
15  mm.  The  color  curves  for  both  the  cholesterol  and 
naphthol  green  B  appear  to  fall  in  a  straight  line  so  that 
readings  somewhat  above  or  below  the  standard  are 
accurate. 

Calculation. — If  a  cholesterol  standard  containing 
0.4  mg.  to  5  c.c.,  or  naphthol  green  B  standard  of 
equivalent  strength,  are  employed,  the  following  formula 
may  be  used  for  the  calculation : 


FIG.  93. — EXTRACTION 
APPARATUS  FOR  CHOLES- 
TEROL DETERMINATION. 

(From  Myers:  "Prac- 
tical Chemical  Analysis 
of  Blood,"  C.  V. 
Mosby  Co.,  St.  Louis, 
1921). 


~  X  0.0004  X  —  X  100  =  Cholesterol  content  of 

K  5 

blood  in  per  cent, 


for  100  c.c. 


in  which  S  stands  for  the  depth  of  standard  in  mm., 
R  for  the  reading  of  the  unknown,  0.0004  the  equiva- 
lent amount  of  cholesterol  in  5  c.c.  of  chloroform,  D 
the  dilution  of  the  chloroform  extract  from  the  i  c.c.  of 
blood,  5  the  dilution  of  the  standard  and  100  the  factor 
For  example : 


-  X  0.0004  X  -    X  100  =  o.i 60  per  cent. 
15  5 


Interpretation. — Normal  blood  serum  contains  from  0.15  to  o.i 8 
per  cent  of  cholesterol  and  whole  blood  about  0.14  to  0.17  per  cent. 
Values  of  from  0.170  to  0.350  have  been  noted  in  chronic  and  acute 
nephritis.  In  diabetes,  values  of  0.150  to  0.300,  and  in  lipemia  ex- 
tremely high  values  (up  to  3.6  per  cent)  are  found.  An  increase 
is  also  found  in  pregnancy.  In  -cholelithiasis  high  values  are  fre- 
quently obtained.  In  pernicious  anemia  values  as  low  as  0.07  per 
cent  are  noted.  Cholesterol  is  increased  by  a  high  lipoid  diet  and 
decreased  by  a  diet  low  in  cholesterol. 

1  In  order  to  get  the  proper  temperature  for  color  development  in  warm  weather  it  is 
advisable  either  to  keep  the  reagents  in  a  cool  place  or  to  insert  the  tubes  in  water  during 
the  development  of  the  color. 


BLOOD   ANALYSIS  293 

(6)  (Method  of  Bloor). — Principle. — The  method  consists  in  the  application  of 
the  Autenrieth-Funk  procedure1  to  the  alcohol-ether  extract  of  blood  or  serum 
prepared  as  for  the  determination  of  fat  (see  nephelometric  methods). 

Procedure. — Measure  10  c.c.  of  the  extract  into  a  small  beaker,  and  evaporate 
just  to  dryness  on  the  water-bath  or  electric  stove.  (Any  heating  after  dryness  is 
reached  produces  a  brownish  color,  which  makes  the  determination  difficult  or 
impossible.) 

Extract  the  cholesterol  from  the  dry  residue  by  boiling  out  3  or  4  times  with 
small  portions  (2-3  c.c.)  of  chloroform  and  decanting..  Evaporate  the  combined 
extracts  to  a  little  less  than  5  c.c.,  transfer  to  a  10  c.c.  graduated  cylinder,  and 
make  the  volume  up  to  5  c.c.  A  little  turbidity  does  not  matter,  since  it  disappears 
on  adding  the  reagents.  Measure  5  c.c.  of  a  standard  cholesterol  solution  in  chloro- 
form, containing  0.5  mg.  of  cholesterol  into  a  similar  10  c.c.  graduate.  Add  to 
each  2  c.c.  of  acetic  anhydride  and  o.i  c.c.  of  concentrated  H2SO4.  Mix  the  solu- 
tions by  inverting  two  or  three  times,  and  set  the  cylinders  in  the  dark  for  15 
minutes;  then  transfer  the  solutions  to  the  colorimeter  cups,  and  compare  as  usual, 
setting  the  standard  at  15  mm.2 

Interpretation. — See  above. 

4.  Calcium.  Method  of  Halverson  and  Bergeim.3 — Principle.— The  method 
depends  upon,  (i)  the  removal  of  protein  by  means  of  sodium  picrate  and  heat, 

(2)  the  precipitation  of  calcium  from  the  protein  free  material  as  the  oxalate,  and 

(3)  titration  of  the  calcium  oxalate  with  very  dilute  standard  potassium  per- 
manganate solution. 

Procedure. — A.  Removal  of  Protein. — Whole  blood  is  preserved  with  powdered 
sodium  citrate  to  make  approximately  1.5  per  cqnt.  An  additional  i  per  cent 
of  citrate  should  be  added  to  plasma  if  this  is  not  to  be  analyzed  at  once.  Direc- 
tions given  below  are  for  serum  or  plasma.  Twice  the  quantity  of  whole  blood 
should  be  employed  and  reagents  increased  proportionately. 

Pipette  5  c.c.  of  serum  or  plasma  into  a  50  c.c.  volumetric  flask  containing 
exactly  20  c.c.  of  distilled  water.  Rinse  by  once  drawing  the  solution  up  into 
the  pipette.  While  rotating  the  flask  add  from  a  pipette  5  c.c.  (i  c.c.  per  c.c.  of 
plasma  or  serum)  of  a  4  per  cent  solution  of  sodium  picrate.4  In  the  same  manner 
add  slowly  5  c.c.  of  hydrochloric  acid  (1:2).  Heat  in  a  boiling  water-bath  with 
occasional  rotation  for  15  minutes.  Cool  to  a  little  below  room  temperature  in 
cold  water.  Pour  onto  a  folded  calcium-free  filter  paper  and  allow  to  drain  well. 

B.  Precipitation  of  Calcium.— Measure  an  aliquot  (usually  25  c.c.)  of  the  filtrate 
into  a  50  c.c.  Erlenmeyer  flask  (Pyrex).  Neutralize  cautiously  with  concentrated 
ammonium  hydrate  added  drop  by  drop  from  a  burette,  using  one  or  two  drops  of 

1  Bloor:  Jour.  Biol.  Chem.,  24,  227,  1916;  29-,  437,  1917. 
Autenrieth  and  Funk:  Munch,  med.  Wochnschr.,  69, .1243,  1913. 

2  The  cement  of  the  colorimeter  cups  must,  of  course,  not  be  soluble  in  chloroform. 
Plaster-of-Paris  has  been  found  satisfactory,  or  even  ordinary  glue,  if  the  cups  are  not 
used  for  any  other  purpose. 

3  Halverson  and  Bergeim:  Jour.  Biol.  Chem.,  32,  159,  1917.    For  colorimetric  method 
see  Marriott  and  Rowland:  Jour.  Biol.  Chem.,  32,  233,  1917  and  for  nephelometric  method 
seeLyman:  Jour.  Biol.  Chem.,  29,  169,  1917;  see  also  the  microtitration  method  of  Kramer 
and  Rowland:  Jour.  Biol.  Chem.  43,  35,  1920. 

4  Sodium  Picrate  Solution,  4  Per  Cent. — To  40  gm.  of  dry  purified  picric  acid  add  a 
little^  calcium-free  water  and  10  gm.  of  highest  purity  anhydrous  sodium   carbonate 
(calcium-free)  dissolved  in  50  c.c.  of  water.     Dilute  to  i  liter.     Shake  until  the  picric  acid 
is  completely  dissolved.     Add  concentrated  hydrochloric  acid  until  a  slight  permanent 
precipitate  of  picric  acid  forms.     Filter  through  highest  grade  filter  paper. 


2  94  PHYSIOLOGICAL  CHEMISTRY 

alizarin  indicator  solution  (0.2  per  cent).  Titrate  back  until  faintly  acid  with 
approximately  o.5/N  hydrochloric  acid.  McCrudden's  method  is  then  followed. 
Add  from  a  burette  2.5  c.c.  of  the  hydrochloric  acido.5/N  mentioned  above  and  then 
the  same  amount  of  2.5  per  cent  oxalic  acid.  To  the  boiling  solution  add  dropwise 
in  two  portions  2.5  c.c.  of  3  per  cent  ammonium  oxalate.  Digest  at  near  boiling 
for  15  minutes. 

Cool  in  ice  water  to  room  temperature  or  lower.  Add  another  drop  of  alizarin 
and  also  dropwise  from  a  burette  2.5  c.c.  of  20  per  cent  sodium  acetate  solution 
while  rotating  the  flask,  or  if  found  necessary  add  until  the  alizarin  just  begins 
to  change  color.  Allow  to  stand  over  night  (or  at  least  4  hours  after  10  minutes' 
shaking). 

Transfer  completely  to  a  50  c.c.  round  bottom  centrifuge  tube  with  the  aid 
of  a  little  water  and  whirl  for  about  3  minutes  at  1500  revolutions  per  minute. 
With  an  automatic  siphon  draw  off  the  supernatant  liquid  at  first  rapidly  and  then 
gently  to  within  a  drop  or  two.  Wash  with  cold  distilled  water  (i5-2o°C.)  first 
adding  about  20  c.c.,  washing  down  the  sides  and  rotating  the  tube.  Then  add 
more  water  from  the  wash  bottle  to  within  about  1.75  cm.  of  the  top  of  the  tube 
(approximately  50- c.c.).  Placing  the  metacarpal  portion  of  the  palm  of  the  hand 
at  the  thumb  over  the  mouth  of  the  tube  shake  vigorously  for  5  to  10  seconds. 
Centrifuge  again.  Siphon  off  to  within  one  or  two  drops  and  titrate. 

C.  Titration. — To  the  precipitates  in  50  c.c.  centrifuge  tubes  add,  with  shaking, 
4  c.c.  of  5  per  cent  sulphuric  acid  (very  faintly  tinged  with  potassium  permanganate). 
Place  in  a  water-bath  at  65°C.  until  the  tubes  approach  the  temperature  of  the  bath. 
Remove  and  titrate  rapidly  with  an  approximately   o.oi33/N  potassium  per- 
manganate solution,1    with   moderate  shaking  using  a  white  background.    A 
burette  of  10  c.c.  capacity  with  which  readings  can  be  readily  estimated  to  o.oi 
c.c.  is  desirable. 

The  end  point  is  attained  when  a  faint  but  definite  pink  color  persists  for  a 
minute  or  longer  on  gentle  shaking  and  standing.  If  the  precipitate  has  not  been 
contaminated  the  end  point  will  be  sharp  to  o.oi  c.c.  The  sulphuric  acid  must  be 
brought  in  contact  with  all  parts  of  the  tube  as  far  up  as  the  original  solution  ex- 
tended. The  burette  reading  should  be  corrected  for  the  small  amount  of  per- 
manganate required  to  titrate  4  c.c.  of  the  sulphuric  acid  to  the  same  end  point. 

D.  Calculation. — i  c.c.  of  b.oi33/N  potassium  permanganate  is  equivalent  to 
0.267  mg-  of  calcium.     The  exact  factor  for  a  given  solution  must  be  determined 
by  standardization.     Multiply  the  number  of  c.c.  used  by  this  factor  to  obtain 
the  amount  of  calcium  in  the  25  c.c.  of  filtrate.     If  blank  on  reagents  is  not  negligible 
deduct.     Multiply  by  28  to  get  mg.  of  Ca  per  100  c.c.  of  serum  or  plasma. 

Nephelometric  Methods 

The  Nephelometer. — The  nephelometer  is  an  instrument  for 
measuring  the  density  of  precipitates  and  thus  determining  the  amount 
of  any  substance  which  can  be  obtained  in  the  form  of  a  suitable 
suspension.  It  is  somewhat  similar  in  form  and  principle  to  a  colori- 
meter. It  differs  from  the  latter  in  that  the  light  which  reaches  the 
eye  is  not  transmitted  light,  which,  on  the  contrary,  is  excluded,  but 

1  For  the  method  of  preparing  this  dilute  standard  permanganate  solution  see  Halverson 
and  Bergeim:  Jour.  Ind.  Eng.  Chem.,  10,  119,  1918. 


BLOOD  ANALYSIS 


295 


light  reflected  from  the  particles  of  the  suspension.  The  brightness 
of  the  two  fields  is  compared  instead  of  their  colors.  It  is  adapted 
particularly  for  the  determination  of  substances  that  in  very  dilute 
solution  may  be  precipitated  in  the  form  of  suspensions  which  do  not 
agglutinate  appreciably  in  the  time  required  for  making  readings 
(10-20  minutes).  The  method  has  been  adapted  to  the  determination 
of  proteins  in  digestion  mixtures,  milk,  urine,  etc.;1  nucleic  acids;2 
chlorides,8  phosphates,  and  phosphatides  in  blood,  etc.;4  fats  in  milk, 
blood,  etc.;5  acetone  bodies  in  urine  and  blood;6  uric  acid  and  purine 
bases;7  ammonia;8  calcium;9  silver,  etc., 
and  is  continually  finding  new  applica- 
tions. It  is  possible  to  determine  very 
minute  amounts  of  substances,  entirely 
outside  of  the  range  of  gravimetric 
methods  of  analysis,  and  hence  the 
procedure  may  be  used  where  the 
amount  of  material  is  very 'limited.  If 
properly  carried  out  the  limits  of  error 
of  the  method  are  not  greater  than  those 
of  the  colorimetric  methods  commonly 
used.  Below  will  be  found  descriptions 
of  and  figures  representing  two  satisfac- 
tory types  of  nephelometer. 

The    Duboscq    colorimeter    has    been 
adapted   for  nephelometric  purposes   by 
Kober10andbyBloor.u   Bloor's  nephelom- 
eter is  illustrated  in  Figs.  94  and  95.    The  FlG  94._BLOOR,S  NEPHELOMETEK. 
brass    plate     carrying     the     colorimeter 

plungers  is  replaced  by  the  plate  A  with  two  slots  in  which  are  sup- 
ported the  nephelometer  tubes  B  with  their  flanges  resting  on  the  edges 
of  the  slots.  The  slots  are  so  cut  that  the  center  lines  of  the  tubes  are 
exactly  in  line  with  the  centers  of  the  lower  openings  of  the  prism 
case  E.  If  desired  they  may  be  countersunk  to  receive  the  flanges. 

1  Kober:  Jour.  Biol.  Chem.,  13,  485,  1913;  Jour.  Am.  Ch.  Soc.,  35,  1585,  1913;  Folin 
and  Denis:  Jour.  Biol.  Chem.,  18,  273,  1914. 

1  Kober  and  Graves:  Jour.  Am.  Chem.  Soc.,  36,  1304,  1914. 

•Richards:  Zeitschr.  f.  anorg.  Chem.,  7,  269,  1895. 

4Greenwald:  Jour.  Biol.  Chem.,  21,  29,  1915;  Bloor:  Jour.  Biol.  Chem.,  22,  133,  1915; 
Kober  and  Egerer:  Jour.  Am.  Chem.  Soc.,  37,  2373,  1915. 

•Bloor:  Jour.  Biol.  Chem.,  17,  377,  1914;  /.  Am.  Chem.  Soc.,  36,  1300,  1914. 

'Folin  and  Denis:  Jour.  Biol.  Chem.,  18,  263,  1914;  Marriott:  same,  16,  289,  1913.. 

7  Graves  and  Kober:  Jour.  Am.  Chem.  Soc.,  37,  2430,  1915. 

•Graves:  /.  Am.  Chem.  Soc.,  37,  1181,  1915 

'Lyman:  Jour.  Biol.  Chem.,  21,  551,  1915. 

10 Kober:  Jour.  Biol.  Chem.,  13,  485,  1913;  Jour.  Am.  Chem.  Soc.,  35,  1585,  1913. 
11  Bloor:  Jour.  Biol.  Chem.,  22,  145,  1915. 


296 


PHYSIOLOGICAL   CHEMISTRY 


The  colorimeter  cups  are  replaced  by  the  jackets  C  which  project 
through  the  holes  in  the  cup  supports  F  and  are  supported  on  them 
by  the  collars  D.  They  move  when  the  cup  supports  move.  The 
mirror  is  turned  to  the  horizontal  position  so  that  it  reflects  no  light. 
The  light  in  the  nephelometer  comes  from  in  front  and  not  from  below 
(see  Fig.  95).  The  nephelometer  tubes  are  small  test-tubes  100X15 
mm.,  preferably  made  from  the  same  sample  of  colorless  glass  tubing 
so  that  they  are  of  exactly  the  same  bore.  The  flanges  at  the  top  should 
be  well  made  so  that  the  tubes  rest  firmly  and  evenly  in  the  slots.  The 
glass  should  be  as  free  as  possible  from  imperfections  and  striations. 


— st 


*  -^ 


PATH  OF  LIGHT 


,J 


PARTITION  • 


F-f$ 


CURTAIN 


FIG.  95. — NEPHELOMETER  IN  POSITION,  SHOWING  RELATION  TO  SOURCE  OF  LIGHT. 

After  the  tubes  are  made  and  fitted  into  place  the  jackets  are  moved  up 
on  each  tube  by  means  of  the  rack  and  pinion  until  the  indicator  on  the 
scale  is  exactly  at  zero.  Marks  are  made  on  each  tube  at  the  point 
reached  by  the  top  of  the  jacket  and  the  portion  of  the  tube  above  that 
point  is  made  opaque  by  a  ring  BI  of  black  paper  or  paint.  Tubes 
and  jackets  are  then  marked  right  and  left  and  always  used  on  the 
same  side.  Since  it  is  rare  to  find  two  tubes  which  when  filled  with  the 
same  solution  give  exactly  the  same  readings  it  is  necessary  to  take  this 
fact  into  account  and  correct  accordingly. 

The  jackets  C  are  made  of  tubing  (metal  or  glass)  a  little  larger 
than  the  tubes  and  about  the  same  length  (they  should  clear  the 
mirror  when  it  is  turned  horizontal),  closed  at  the  bottom  and  made 
light  tight  by  black  paint  or  paper.  The  collars  D  supporting  the 
jackets  may  be  made  of  cork  or  more  permanently  of  metal.  A  little 
cotton  wool  in  the  bottom  of  the  jackets  will  prevent  breakage  if  the 
tubes  should  fall  into  the  jackets. 


BLOOD   ANALYSIS 


297 


The  openings  in  the  prism  case,  particularly  the  lower  ones,  should 
be  protected  against  accidental  splashing  by  thin  glass  plates  (thick 
cover  slips)  which  are  held  in  place  by  a  little  glue. 

Artificial  light  is  necessary  and  the  lamp  should  be  enclosed  in 
a  tight  box  into  one  end  of  which  the  nephelometer  fits  snugly.  A 
partition  extending  part  way  up  the  box  as  shown  in  the  diagram 
(Fig.  95)  serves  the  double  purpose  of  shutting  off  the  light  from 
the  lower  part  of  the  instrument 
and  of  providing  a  stop  against 
which  the  instrument  is  pushed, 
so  that  its  distance  from  the  light 
is  kept  constant.  The  box  is  con- 
veniently made  without  a  bottom 
and  the  end  closed  with  a  dark 
curtain  after  the  nephelometer  is 
pushed  into  place.  The  inside  of 
the  box  should  be  painted  black. 
A  dark  room  is  desirable  but  not 
necessary,  as  the  instrument  may 
be  used  satisfactorily  in  a  room 
darkened  by  a  dark  shade  or  even 
in  a  dark  corner  of  the  laboratory. 

The  relations  of  the  nephelo- 
meter and  the  light  source  may 
be  seen  in  the  diagram,  Fig.  95. 
The  lamp  used  is  an  ordinary  50- 
watt  tungsten  ("Mazda")  sup- 
ported by  a  bracket  about  30  cm. 
from  the  nephelometer  and  at  the 
height  of  the  nephelometer  tubes. 
The  change  from  one  instrument 
to  the  other  can  be  made  in  one 
or  two  minutes,  since  it  consists 
essentially  only  in  unscrewing 
the  brass  plate  carrying  the  plun- 
gers and  screwing  on  the  plate  to  carry  the  nephelometer  tubes.  The 
extra  parts  needed,  plate,  tubes,  and  jackets,  are  few  and  can  be  made 
if  necessary  from  material  at  hand  in  any  laboratory  and  by  anyone 
with  a  slight  degree  of  mechanical  skill.1 

The  above  description  applies  only  to  the  later  type  of  colorime- 

1  The  extra  parts  necessary  for  the  conversion  of  the  colorimeter  into  the  nephelometec 
may  be  obtained  from  the  International  Instrument  Co.  of  Cambridge,  Mass. 


FIG.  96. — KOBER'S  NEPHELOMETER 

COLORIMETER. 

(From  Journal  of  Biological  Chemistry, 
29,  155,  1917.) 


PHYSIOLOGICAL   CHEMISTRY 

ter  where  the  cups  move  and  the  prisms  are  stationary.  The  changes 
required  to  convert  the  older  type  of  instrument  are  more  complicated 
and  scarcely  to  be  advised  unless  the  instrument  is  to  have  fairly 
continuous  use  as  a  nephelometer.  If  the  change  is  desired  the  nephe- 
lometer tubes  are  to  be  supported  in  the  same  way  as  above,  but  the 
jackets  must  be  carried  on  special  brackets  which  are  made  to  replace 
the  brackets  carrying  the  plungers.  The  nephelometer  tubes  must  be 
stationary,  the  jackets  being  the  movable  parts. 

Kober1  has  devised  a  combined  colorimeter  and  nephelometer  less 
expensive  than  the  Duboscq  apparatus  and  which  may  be  obtained 
in  this  country.2  A  cut  of  this  nephelometer-colorimeter  is  given  in 
Fig.  96,  page  297. 

Nephelometric  Calculations. — The  amounts  of  precipitate  in  solu- 
tions examined  nephelometrically  is  not  exactly  inversely  proportional 
to  the  readings  of  the  scale.  When  the  concentration  of  the  unknown 
and  of  the  standard  are  within  10  per  cent  of  each  other  (or  within 
about  20  per  cent  if  the  readings  are  made  at  depths  as  great  as  50- 
60  mm.)  accurate  results  may  however  be  obtained  directly.  If  the 
variations  are  greater  than  this  a  correction  is  necessary.  Kober3 
has  proposed  an  equation  to  supply  this  correction  and  thus  make 
possible  very  accurate  work  under  conditions  of  moderate  variations 
of  concentration.  The  equation  is  as  follows: 

5       (i  —  x)sk 


or 


2y 


where  y  =  height  of  unknown  solution,  on  the  left  side  of  the  instru- 
ment, when  standard  solution  is  kept  on  the  right  side  at  a  definite 
height,  5  =  height  of  standard  solution  on  the  left  side  and  %  =  the 
ratio  of  the  concentrations  of  the  two  solutions. 

T£ 

k  =  —  where  K  =  a  constant,  obtained  by  substitution  of  standardi- 

s  .  . 

zation  values  of  s,  y,  and  x.  The  instrument  should  be  checked  up 
for  each  series  of  analyses  by  reading  the  standard  against  itself  and 
determining  the  potential  height  of  the  standard  solution  by  reading 
the  scale  on  the  left  side  when  the  solution  on  the  right  side  is  kept  at  a 
definite  height,  and  the  two  are  matched. 

1  Kober:  Jour.  Ind.  and  Eng.  Chem.,  7,  843,  1915;  Jour.  Biol.  Chem.,  29,  155,  1917. 
*  The  instrument  is  manufactured  by  the  Klett  Manufacturing  Co.,  202  E.  46th  St., 
New  York  City. 

8  Kober:  J.  Am.  Chem.  Soc.,  37,  2379,  1915;  Jour.  Biol.  Chem.,  13,  485,  1913. 


BLOOD   ANALYSIS  299 

i.  Fat. — Nephelometric  Method  of  Bloor,1 — Principle. — The  protein  is  precipi- 
tated with  alcohol  and  ether  and  the  fatty  acid  in  the  extract  determined  nephelo- 
metrically  after  saponification. 

Procedure. — Extraction. — About  2  c.c.  of  blood  are  drawn  from  the  vein  with  a 
graduated  syringe  and  run  at  once  with  stirring  into  a  weighed  graduated  flask 
containing  about  40  volumes  of  a  mixture  of  3  parts  alcohol  and  i  part  ether. 
After  again  weighing  to  find  the  weight  of  blood  added,  the  solution  is  raised  to 
boiling  in  a  water-bath,  cooled  under  the  tap,  made  to  volume  with  alcohol-ether 
mixture,  mixed  and  filtered.  The  filtrate  is  water  clear  and  almost  colorless. 

Determination. — From  5-20  c.c.  of  the  extract  (containing  about  2  mg.  of  fat) 
are  measured  with  a  pipette  into  a  small  beaker  and  saponified  by  evaporating 
nearly  but  not  quite  to  dryness  with  2  c.c.  of  N/i  sodium  ethylate.  The  residue  is 
heated  just  to  boiling  after  the  addition  of  5  c.c.  of  alcohol-ether,  and  50  c.c.  of 
distilled  water  are  added. 

A  similar  solution  of  the  standard  is  prepared  by  adding  5  c.c.  of  the  standard 
fatty  acid  solution2  from  a  pipette  with  stirring  to  50  c.c.  of  distilled  water.  To 
the  standard  and  to  the  test  solutions  are  added  simultaneously  from  pipettes  and 
with  stirring  10  c.c.  portions  of  dilute  (1:3)  hydrochloric  acid  and  the  solutions 
allowed  to  stand  for  five  minutes,  after  which  they  are  transferred  to  the  comparison 
tubes  of  the  nephelometer  (see  Fig.  94,  p.  294).  Several  readings  should  be  taken 
and  averaged.  The  standard  tube  should  always  be  on  the  same  side.  See  dis- 
cussion of  nephelometer  (page  294)  for  details  as  to  reading.  The  results  repre- 
sent the  amount  of  total  fat  (fatty  acids  and  cholesterol)  in  the  blood,  expressed 
as  oleic  acid.  The  fat  of  the  corpuscles  is  not  completely  extracted,  and  it  should 
be  borne  in  mind  that  other  lipoids  as  cholesterol  are  included  in  the  results. 
Cholesterol  may  be  determined  separately  and  subtracted  from  the  result  for  total 
fat.  It  may  also  be  determined  in  a  part  of  the  blood  extract  as  prepared  above 
by  a  modified  Autenrieth-Funk  procedure.3  Methods  have  also  been  devised  for 
the  determination  of  the  phosphatides  of  blood.4 


Other  Methods  of  Blood  Analysis 

Methods  for  determining  the  alkali  reserve  of  the  blood 
will  be  found  in  the  following  chapter.  Important  methods 
have  been  developed  also  for  magnesium,5  sodium,6  potassium,7 

1  Bloor:  Jour.  Biol.  Chem.,  17,  377,  1914;  23,  317,  1915. 

2  The  standard  solution  used  is  an  alqohol-ether  solution  of  pure  oleic  acid  of  which 
5  c.c.  contain  about  2  mg.  of  the  acid.    The  alcohol  and  ether  used  for  the  standard  are 
freshly  redistilled  absolute  alcohol  and  pure  dry  ether. 

3  Bloor:  Jour.  Biol.  Chem.,  23,  317,  1915. 

4  Green wald:  Jour.  Biol.  Chem.,  21,  29,  1915. 

Bloor:  Jour.  Biol.  Chem.,  22,  133,  1915,  23,  317,  1915. 
Kober  and  Egerer:  /.  Am.  Chem.  Soc.,  37,  2373,  1915. 
Taylor  and  Miller:  Jour.  Biol.  Chem.,  18,  215,  1914. 
For  other  nephelometric  methods  see  Chapters  XVIII  and  XXVII. 
6  Denis,  W.:  Jour.  Biol.  Chem.,  41,  363,  1920;  Marriot,  W.  McK.,  and  Rowland,  J. 
Jour.  Biol.  Chem.,  32,  233,  1917. 

6  Kramer,  B.:  Jour.  Biol.  Chem.,  41,  <2'63,  1920;  Doisey,  E.  A.,  and  Bell,  R.  D.:  Jour. 
Biol.  Chem.,  45,  313,  1921;  Kramer  and  Tisdall:  Jour.  Biol.  Chem.,  46,  467,  1921. 

7  Kramer,  B.:  Jour.  Biol.  Chem.,  41,  263,  1920;  Kramer,  B.  and  Tisdall,  F.F.:  Jour. 
Biol.  Chem.,  46,  339,  1921;  Klausen,  S.  W.;  Jour.  Biol.  Chem:,  36,  479,  1918. 


3oo 


PHYSIOLOGICAL  CHEMISTRY 


phosphate,1  iron,2  iodin,3  phenols,4  amino  acids,5  amylase6  and  other 
substances. 

Spectroscopic  Examination  of  Blood3 

Either  the  angular- vision  spectroscope  (Figs.  98  and  99)  or  the 
direct-vision  spectroscope  (Fig.  97)  may  be  used  in  making  the  spec- 
troscopic  examination  of  the  blood.  For  a  complete  description  of 
these  instruments  the  student  is  referred  to  any  standard  text-book  of 
physics. 


FIG.  97. — DIRECT-VISION  SPECTROSCOPE. 

i.  Oxyhemoglobin. — Examine  dilute  (1:50)  defibrinated  blood  spectro- 
scopically.  Note  the  broad  absorption  band  between  D  and  E.  Continue  the 
dilution  until  this  single  broad  band  gives  place  to  two  narrow  bands,  the  one 
nearer  the  D  line  being  the  narrower.  These  are  the  typical  absorption  bands 


FIG.  98. — ANGULAR-VISION  SPECTROSCOPE  ARRANGED  FOR  ABSORPTION  ANALYSIS. 

of  oxyhemoglobin  obtained  from  dilute  solutions  of  blood.  Now  dilute  the  blood 
very  freely  and  note  that  the  bands  gradually  become  more  narrow  and,  if  the 
dilution  is  sufficiently  great,  they  finally  entirely  disappear. 

^ell,  R.  D.,  and  Doisy,  E.  A.:  Jour.  Biol.  Chem.,  44,  55,  1920;  Bloor,  W.  R.:  Jour. 
Biol.  Chem.,  45,  171,  1920;  Meings,  E.  B.:  Jour.  Biol.  Chem.,  36,  335,  1918;  Bloor  W. 
R.:  Jour.  Biol.  Chem.,  36,  33,  1918. 

2  Berman,  L.:  Jour.  Biol.  Chem.,  35,  231,  1918. 

3  Kendall, 'E.  G.,  and  Richardson,  F.  S.:  Jour.  Biol.  Chem.,  43,  161,  1920. 

4  Benedict,  S.  R.,  and  Theis,  R.  C.:  Jour.  Biol.  Chem.,  36,  95,  1918. 

6Bock,  J.  C.:  Jour.  Biol.  Chem.,  28,  357,  1917;  Okada,  S.:  Jour.  Biol.  Chem.,  33,  325, 
1918;  Gary  C.  A.:  Jour.  Biol.  Chem.,  43,  477,  1920;  Van  Slyke,  D.  D.,  and  Meyer,  V.  C.: 
Jour.  Biol.  Chem.,  12,  399,  1912. 

6 Lewis,  D.  S.,  and  Mason,  E.  H.:  Jour.  Biol.  Chem.,  44,  455,  1920. 


BLOOD   ANALYSIS 


301 


2.  Hemoglobin  (so-called  Reduced  Hemoglobin). — To  blood  which  has  been 
diluted  sufficiently  to  show  well-defined  oxyhemoglobin  absorption  bands  add  a 
small  amount  of  Stokes*  reagent. l  The  blood  immediately  changes  in  color  from 
a  bright  red  to  violet-red.  The  oxyhemoglobin  has  been  reduced  through  the 
action  of  Stokes'  reagent  and  hemoglobin  (so-called  reduced  hemoglobin)  has 
been  formed.  This  has  been  brought  about  by  the  removal  of  some  of  the  loosely 
combined  oxygen  from  the  oxyhemoglobin.  Examine  this  hemoglobin  spectro- 
scopically.  Note  that  in  place  of  the  two  absorption  bands  of  oxyhemoglobin  we 
now  have  a  single  broad  band  lying  almost  entirely  between  D  and  E.  This  is 
the  typical  spectrum  of  hemoglobin.  If  the  solution  showing  this  spectrum  be 
shaken  in  the  air  for  a  few  moments  it  will  again  assume  the  bright  red  color  of 
oxyhemoglobin  and  show  the  characteristic  spectrum  of  that  pigment. 


S 


FIG.  99. — DIAGRAM  OF  ANGULAR-VISION  SPECTROSCOPE.  (Long.) 
The  white  light  F  enters  the  collimator  tube  through  a  narrow  slit  and  passes  to  the 
prism,  P,  which  has  the  power  of  refracting  and  dispersing  the  light.  The  rays  then  pass  to 
the  double  convex  lens  of  the  ocular  tube  and  are  deflected  to  the  eyepiece  E.  The  dotted 
lines  show  the  magnified  virtual  image  which  is  formed.  The  third  tube  contains  a  scale 
whose  image  is  reflected  into  the  ocular  and  shown  with  the  spectrum.  Between  the  light 
F  and  the  collimator  slit  is  placed  a  cell  to  hold  the  solution  undergoing  examination. 

3.  Carbon  Monoxide  Hemoglobin.— The  preparation  of  this  pigment  may  be 
easily  accomplished  by  passing  ordinary  illuminating  gas2  through  defibrinated 
ox-blood.  Blood  thus  treated  assumes  a  brighter  tint  (carmine)  than  that  im- 
parted by  oxyhemoglobin.  In  very  dilute  solution  oxyhemoglobin  appears 
yellowish  red  whereas  carbon  monoxide  hemoglobin  under  the  same  conditions 
appears  bluish  red.  Examine  the  carbon  monoxide  hemoglobin  solution  spec- 
troscopically.  Observe  that  the  spectrum  of  this  body  resembles  the  spectrum 
of  oxyhemoglobin  in  showing  two  absorption  bands  between  D  and  E.  The 
bands  of  carbon  monoxide  hemoglobin,  however,  are  somewhat  nearer  the  violet 
end  of  the  spectrum.  Add  some  Stokes'  reagent  to  the  solution  and  again  ex- 
amine spectroscopically.  Note  that  the  position  and  intensity  of  the  absorption 
bands  remain  unaltered. 

1  Stokes*  reagent  is  a  solution  containing  2  per  cent  ferrous  sulphate  and  3  per  cent 
tartaric  acid.     When  needed  for  use  a  small  amount  should  be  placed  in  a  test-tube  and 
ammonium  hydroxide  added  until  the  precipitate  which  forms  on  the  first  addition  of  the 
hydroxide  has  entirely  dissolved.    This  produces  ammonium  f  err otartr ate  which  is  a  reduc- 
ing agent. 

2  The  so-called  water  gas  with  which  ordinary  illuminating  gas  is  diluted  contains  usu- 
ally as  much  as  20  per  cent  of  carbon  monoxide  (CO). 


302  PHYSIOLOGICAL  CHEMISTRY 

The  following  is  a  delicate  chemical  test1  for  the  detection  of  carbon  monoxide 
hemoglobin : 

Tannin  Test. — Divide  the  blood  to  be  tested  into  two  portions  and  dilute  each 
with  4  volumes  of  distilled  water.  Place  the  diluted  blood  mixtures  in  two  small 
flasks  or  large  test-tubes  and  add  20  drops  of  a  10  per  cent  solution  of  potassium 
ferricyanide.2  Allow  both  solutions  to  stand  for  a  few  minutes,  then  stopper  the 
vessels  and  shake  one  vigorously  for  10-15  minutes,  occasionally  removing  the 
stopper  to  permit  air  to  enter  the  vessel.3  Add  5-10  drops  of  ammonium  sulphide 
(yellow)  and  10  c.c.  of  a  10  per  cent  solution  of  tannin  to  each  flask.  The  contents 
of  the  shaken  flask  will  soon  exhibit  the  formation  of  a  dirty  olive-green  precipitate, 
whereas  the  flask  which  was  not  shaken  and  which,  therefore,  still  contains  car- 
bon monoxide  hemoglobin,  will  exhibit  a  bright  red  precipitate,  characteristic  of 
carbon  monoxide  hemoglobin.  This  test  is  more  delicate  than  the  spectroscopic 
test  and  serves  to  detect  the  presence  of  as  low  a  content  as  5  per  cent  of  carbon 
monoxide  hemoglobin.  . 

4.  Neutral  Methemoglobin. — Dilute  a  little  defibrinated  blood  (i :  10)  and 
add  a  few  dro^s  of  a  freshly  prepared  10  per  cent  solution  of  potassium  ferricya- 
nide.   Shake  this  mixture  and  observe  that  the  bright  red  color  of  the  blood  is 
displaced  by  a  brownish  red.    Now  dilute  a  little  of  this  solution  and  examine  it 
spectroscopically.    Note  the  single,  very  dark  absorption  band  lying  to  the  left 
of  D,  and,  if  the  dilution  is  sufficiently  great,  also  observe  the  two  rather  faint 
bands  lying  between  D  and  E  in  somewhat  similar  positions  to  those  occupied  by 
the  absorption  bands  of  oxyhemoglobin.    Add  a  few  drops  of  Stokes'  reagent  to 
the  methemoglobin  solution  while  it  is  in  position  before  the  spectroscope  and  note 
the  immediate  appearance  of  the  oxyhemoglobin  spectrum  which  is  quickly  fol- 
lowed by  that  of  hemoglobin. 

5.  Alkaline  Methemoglobin. — Render  a  neutral  solution  of  methemoglobin, 
such  as  that  used  in  the  last  experiment  (4),  slightly  alkaline  with  a  few  drops  of 
ammonia.     The  solution  becomes  redder  in  color,  due  to  the  formation  of  alkaline 
methemoglobin  and  shows  a  spectrum  different  from  that  of  the  neutral  body'    In 
this  case  we  have  a  band  on  either  side  of  D,  the  one  nearer  the  red  end  of  the 
spectrum  being  much  the  fainter.     A  third  band,  darker  than  either  of  those  men- 
tioned, lies  between  D  and  E  somewhat  nearer  E. 

6.  Alkali  Hematin. — Observe  the  spectrum  of  the  alkali  hematin  prepared  in 
Experiment  17  on  page  269.     Also  make  a  spectroscopic  examination  of  a  freshly 
prepared  alkali  hematin.4    The  typical  spectrum  of  alkali  hematin  shows  a  single 
absorption  band  lying  across  D  and  mainly  toward  the  red  end  of  the  spectrum. 

7.  Reduced  Alkali  Hematin  or  Hemochromogen. — Dilute  the  alkali  hematin 
solution  used  in  the  last  experiment  (6)  to  such  an  extent  that  it  shows  no  absorption 
band.    Now  add  a  few  drops  of  Stokes'  reagent  or  ammonium  sulphide  and  note 
that  tne  greenish-brown  color  of  the  alkali  hematin  solution  is  displaced  by  a 
bright  red  color.    This  is  due  to  the  formation  of  hemochromogen  or  reduced 

1  Sand  (U geskrift  for  Laeger,  76,  1721,  1914;  Abst.  /.  A.  M.  A.,  Nov.  21,  1914)  proposes 
a  potassium  iodide  test  for  carbon  monoxide  hemoglobin  in  blood.  He  claims  0.125  Per 
cent  may  be  detected  by  his  test. 

s  This  transforms  the  oxyhemoglobin  into  methemoglobin. 

3  This  is  done  to  free  the  blood  from  carbon  monoxide  hemoglobin. 

4  Alkali  hematin  may  be  prepared  by  mixing  one  volume  of  a  concentrated  potassium 
hydroxide  or  sodium  hydroxide  solution  and  two  volumes  of  dilute  (i  :  5)  defibrinated  blood. 
This  mixture  should  be  heated  gradually  almost  to  boiling,  then  cooled  and  shaken  for 
a  few  moments  in  the  air  before  examination. 


BLOOD   ANALYSIS  303 

alkali  hematin.  Examine  this  solution  spectroscopically  and  observe  the  narrow, 
dark  absorption  band  lying  midway  between  D  and  E.  If  the  dilution  is  not 
too  great  a  faint  band  may  be  observed  in  the  green  extending  across  E  and  b. 

8.  Acid  Hematin. — To  some  defibrinated  blood  add  half  its  volume  of  glacial 
acetic  acid  and  an  equal  volume  of  ether.     Mix  thoroughly.    The  acidified  etheral 
solution  of  hematin  rises  to  the  top  and  may  be  poured  off  and  used  for  the  spectro- 
scopic  examination.    If  desired  it  may  be  diluted  with  acidified  ether  in^the  ratio 
of  one  part  of  glacial  acetic  acid  to  two  parts  of  ether.     A  distinct  absorption  band 
will  be  noted  in  the  red  between  C  and  D  and  lying  somewhat  nearer  C  than  the 
band  in  the  methemoglobin  spectrum.    Between  D  and  F  may  be  seen  a  rather 
indistinct  broad  band.     Dilute  the  solution  until  this  band  resolves  itself  into  two 
bands.     Of  these  the  more  prominent  is  a  broad,  dark  absorption  band  lying  in  the 
green  between  b  and  F.    The  second,  a  narrow  band  of  faint  outline,  lies  in  the 
light  green  to  the  red  side  of  E.     A  fourth  very  faint  band  may  be  observed  lying 
on  the  violet  side  of  D. 

9.  Acid  Hematoporphyrin. — To  5  c.c.  of  concentrated  sulphuric  acid  in  a  test- 
tube  add  2  drops  of  blood,  mixing  thoroughly  by  agitation  after  the  addition  of 
each  drop.     A  wine-red  solution  is  produced.    Examine  this  solution  spectroscopic- 
ally.   Acid  hematoporphyrin  gives  a  spectrum  with,  an  absorption  band  on  either 
side  of  D,  the  one  nearer  the  red  end  of  the  spectrum  being  the  narrower. 

10.  Alkaline  Hematoporphyrin. — Introduce  the  acid  hematoporphyrin  solution 
just  examined  into  an  excess  of  distilled  water.     Cool  the  solution  and  add  potas- 
sium hydroxide  slowly  until  the  reaction  is  but  slightly  acid.    A  colored  precipitate 
forms  which  includes  the  principal  portion  of  the  hematoporphyrin.     The  presence 
of  sodium  acetate  facilitates  the  formation  of  this  precipitate.     Filter  off  the 
precipitate  and  dissolve  it  in  a  small  amount  of  dilute  potassium  hydroxide.    Alka- 
line hematoporphy  in  prepared  in  this  way  forms  a  bright  red  solution  and  possesses 
four  absorption  bands.    The  first  is  a  very  faint,  narrow  band  in  the  red,  midway 
between  C  and  D;  the  second  is  a  broader,  darker  band  lying  across  D,  principally  to 
the  violet  side.    The  third  absorption  band  lies  principally  between  D  and  E,  ex- 
tending for  a  short  distance  across  E  to  the  violet  side,  and  the  fourth  band  is 
broad  and  dark  and  lies  between  b  and  F.    The  first  band  mentioned  is  the  faintest 
of  the  four  and  is  the  first  to  disappear  when  the  solution  is  diluted. 


CHAPTER  XVII 
RESPIRATION  AND  ACIDOSIS 

Respiration  is  the  process  by  which  oxygen  is  introduced  into  and 
carbon  dioxide  removed  from  the  body.  By  external  respiration  is 
meant  the  gaseous  exchange  in  the  lungs  between  the  blood  in  the 
pulmonary  capillaries  and  the  air  in  the  alveoli.  Internal  respiration 
is  the  similar  exchange  taking  place  in  the  systemic  capillaries  between 
the  blood  and  tissue  elements.  The  actual  oxidation  processes  in 
the  tissue  cells  are  considered  under  metabolism  (Chapter  XXVIII). 

The  table  shows  the  alterations  which  inspired  air  undergoes  in 
passing  through  the  lungs.  Results  are  expressed  in  volume  per  cent.1 


Oxygen 

Carbon  dioxide 

Nitrogen 

Argon 

Inspired  air  . 

2O   04. 

o  03 

78.00 

o  .04 

Expired  air 

1  6  40 

4    I 

78.00 

O.Q4 

It  will  be  seen  that  all  of  the  oxygen  taken  in  is  not  excreted  as  CO2, 
some  of  it  going  to  form  water  and  other  oxidation  products  eliminated 
for  the  most  part  by  the  kidneys. 

The  next  table  shows  the  changes  which  commonly  take  place  in  the 
gaseous  composition  of  the  blood  in  passing  through  the  systemic 
capillaries  (results  also  expressed  in  volume  per  cent). 


02 

CO2      , 

N, 

Arterial  blood  .        ... 

20 

38 

i  .7 

Venous  blood  

12 

4% 

i  .7 

Difference 

8 

7 

o 

Practically  all  of  the  oxygen  of  the  blood  is  carried  in  chemical 
combination  with  the  hemoglobin. 

Practically  all  of  the  COz  is  carried  by  the  blood  as  carbonic  acid 
(H^COa)  and  bicarbonates  (BHCOs)  of  sodium  and  potassium.  These 
always  exist  in  such  relative  proportions  as  to  maintain  the  approxi- 
mately neutral  reaction  of  the  blood.2 

The  alkali  which  combines  with  the  CC>2  and  makes  possible  this 

1  Benedict,  F.  G.,  "Carnegie  Publication"  166,  1912;  Lee,  F.  S.,  Jour.  Ind.  and  Eng. 
Chem.y  6,  247,  1914. 

2  Henderson  L.  J.:  Jour.  Biol.  Chem,  46,.  411,  1921. 

304 


RESPIRATION   AND    ACIDOSIS  305 

maintenance  of  reaction  and  transportation  of  the  C02,  is  furnished  by 
alkali  phosphates  (present  almost  entirely  in  the  red  cells),  the  bicar- 
bonate of  the  blood,  the  plasma  proteins,  and  the  oxyhemoglobin  of  the 
cells.1  As  the  oxyhemoglobin  of  the  blood  passes  into  the  systemic 
capillaries  and  loses  oxygen  to  the  tissues,  it  becomes  more  weakly 
acid  in  character  and  hence  gives  up  its  alkali  more  readily  just  at  the 
time  this  is  needed  to  combine  with  C02  given'  off  by  the  tissue  cells. 
In  the  lungs  the  hemoglobin  of  the  venous  blood  takes  up  more  oxygen 
again,  becomes  more  strongly  acid,  and  takes  back  alkali  from  the 
bicarbonates.  The  hemoglobin  thus  plays  a  very  large  part  in  fur- 
nishing alkali  for  the  transportation  of  CO2.2 

Acidosis  may  be  considered  as  a  condition  brought  about  by  the 
excessive  withdrawal  of  bases  through  the  formation  of  acids  within 
the  body.  Such  an  acidosis  may  occur  in  diabetes  mellitus,  in  certain 
kidney  disorders,  e.g.,  severe  nephritis,  in  childrens  disorders  such 
as  diarrhea,  recurrent  vomiting,  food  intoxication,  etc.  The  acids 
known  to  be  produced  are  acetoacetic  acid  and  0-hydroxybutyric  acid. 
These  along  with  acetone  are  classed  together  as  the  "acetone bodies." 
Not  only  may  an  excessive  acid  formation  or  retention  in  the  body 
accompany  the  various  disorders  mentioned,  but  an  acidosis  may  be  pro- 
duced in  any  normal  person  by  proper  changes  in  diet.  Thus  the  feed- 
ing of  a  diet  which  contains  no  carbohydrate  will  generally  be  followed 
within  24  hours  by  indications  of  acidosis.  The  following  table 
(von  Noorden)  indicates  the  extent  to  which  such  a  "physiological" 
acidosis  may  develop.  Such  acidosis  will  not  result  if  carbohydrate 
to  the  extent  of  50-150  grams  per  day  is  included  in  the  diet.  The 
feeding  of  a  "salt-free"  diet  or  of  a  diet  containing  a  large  excess  of 
acid-forming  foods  such  as  meats,  fish,  cereals  and  eggs  may  also  cause 
acidosis.  In  the  latter  case  (i.e.,  acid-forming  foods)  however,  the 
acidosis  is  not  associated  with  the  formation  of  acetone  bodies. 
ACIDOSIS  ACCOMPANYING  CARBOHYDRATE  WITHDRAWAL 


Day 

Diet 

Excretion  of  acetone  bodies  calcu- 
lated as  /3-hydroxy  butyric  acid 
^                 (grams) 

i 

Protein,  fat  and  carbohydrate 

none 

2 

Protein  and  fat  

0.8 

3 

Protein  and  fat  

1  .0 

4 

Protein  and  fat.  .            .... 

8  7 

Protein  and  fat 

20  o 

6 

Protein,  fat  and  carbohydrate  

2  .2 

1  For  a  discussion  of  the  relative  importance  of  these  factors  see:  Van  Slyke,  D.  D. 
The  Carbon  Dioxide  Carriers  of  the  Blood;  Physiological  Reviews,  i,  141, 1921. 

2  Haggard  and  Henderson:  Jour.  Biol.  Chem.,  45,  189,  1921. 


306  PHYSIOLOGICAL  CHEMISTRY 

Of  the  acetone  bodies,  the  acetoacetic  acid  is  considered  to  be  the 
most  important.  This  acid  has  its  origin  principally  in  fats,  and  to 
a  minor  degree  in  certain  amino  acids  resulting  from  protein  cleavage. 
It  has  been  demonstrated  that  acetoacetic  acid  may  be  formed  in 
the  body  through  the  oxidation  of  butyric  acid,  and  that  the  administra- 
tion of  fats  containing  butyrin  to  diabetics  causes  an  increased  produc- 
tion of  acetoacetic  acid.  Furthermore,  it  is  believed  that  fatty  acids 
higher  than  butyric  acid  in  the  series  also  yield  acetoacetic  acid  by 
oxidation.  In  this  change  the  oxidation  occurs  at  the  0-carbon, 
two  carbon  atoms  at  a  time  being  involved.  As  soon  as  the  oxidation 
proceeds  to  the  butyric  acid  stage  this  acid  is  transformed  into  aceto- 
acetic acid.  In  diabetes  the  body  either  does  not  possess  the  normal 
power  of  oxidizing  acetoacetic  acid  or  else  this  acid  is  produced  in 
excessive  amount.  At  any  rate,  we  find  it  in  blood  and  urine  in  ab- 
normal quantity.  The  relationship  of  acetoacetic  acid  to  fatty  acids 
may  be  expressed  as  follows : 

CH3-CH2-CH2-CH2;CH2-COOH 

Caproic  acid 

lo 

CH3-CH2-CH2-COCH2-COOH 

fo 

CH3-CH2-CH2-COOH 

Butyric  acid 

40 
CH8-CO-CH2-COOH 

Acetoacetic  add 

The  jS-hydroxybutyric  acid  is  formed  from  acetoacetic  acid  by 
reduction.  It  was  originally  believed  that  this  procedure  was  reversed 
and  that  the  acetoacetic  acid  was  formed  from  the  j3-hydroxybutyric 
acid  by  oxidation.  However,  it  has  been  shown  that  the  introduction 
of  jS-hydroxybutyric  acid  into  the  body  is  not  followed  by  an  increased 
acetoacetic  acid  formation,  whereas,  /3-hydroxybutyric  acid  is  formed 
when  acetoacetic  acid  is  introduced.  Therefore,  it  seems  clear  that 
the  acetoacetic  acid  is  the  original  substance  from  which  the  /3-hydroxy- 
butyric acid  is  formed  by  a  process  of  reduction.  The  relationship 
between  the  acetone  bodies  may  be  indicated  in  this  way: 

CH3-CO-CH2-COOH  ->  CH3-COCH3  +  CO2 

Acetoacetic  Acid  Acetone 

I  H  (reduction) 
CH3-CHOH-CH2-COOH 

0-hydroxybutyric  acid 

In  the  normal  body  it  is  probable  that  the  bulk  of  the  acetoacetic 
acid  is  oxidized  to  acetic  acid  and  carbonic  acid  in  turn  and  thence  to 
carbon  dioxide  and  water,  whereas,  in  the  diabetic  organism  this  does 


RESPIRATION    AND    ACIDOSIS  3°7 

not  occur,  at  least  not  to  any  great  extent.  Likewise  in  the  absence 
of  carbohydrate  in  the  diet,  the  oxidation  is  not  complete  and  acetone 
bodies  are  increased  in  amount  in  both  blood  and  urine. 

The  appearance  of  the  "acetone  bodies,"  i.e.,  acetone,  acetoacetic 
acid  and  0-hydroxybutyric  acid  in  the  urine  in  appreciable  quantity  was 
originally  taken  as  the  index  of  an  acidosis  and  the  extent  of  the  acidosis 
was  judged  by  the  estimation  of  the  amount  of  these  bodies  present 
in  the  urine.  That  this  is  not  a  reliable  index  is  shown  by  the  occasional 
observation  of  a  pronounced  acidosis  with  no  appreciable  increase  in 
urinary  acetone  bodies.  A  high  urinary  ammonia  coefficient  (ammonia 
N:  total  N)  was  also  early  looked  upon  as  an  indication  of  acidosis. 
However,  this  factor  is  not  very  useful  in  diagnosis  in  spite  of  the  fact 
that  the  majority  of  acidosis  cases  show  a  high  urinary  ammonia  value. 
Certain  dietetic  changes  may  produce  high  urinary  ammonia,  therefore, 
it  is  not  necessarily  indicative  of  acidosis.  It  is  also  true  that  fatal 
acidosis  has  been  observed  in  uremia,  and  in  nutritional  disorders 
of  infants,  with  no  pronounced  increase  in  the  Ammonia  coefficient. 

With  the  development  of  blood  analysis  the  content  of  these  acetone 
bodies  in  blood  plasma  was  looked  to  as  an  aid  in  the  determination  of 
the  extent  of  acidosis.  But  here  again  the  hope  of  the  clinician  failed 
to  materialize.  Notwithstanding  the  fact  that  acidosis  may  truthfully 
be  considered  as  that  state  of  metabolism  of  which  the  most  constant 
characteristic  is  the  production  of  abnormal  quantities  of  acetone 
bodies,  nevertheless,  it  is  the  consensus  of  the  best  opinion  at  the  pres- 
ent time  that  acidosis  can  be  best  diagnosed  and  its  course  followed 
not  by  the  determination  of  acetone  bodies  in  either  urine  or  blood  but 
by  the  determination  of  certain  other  factors  which  are  more  or  less 
typical  of  acidosis.  These  include  the  following: 

1.  The  determination  of  the  "alkali  reserve''  of  the  blood. 

2.  The  determination  of  the  alkali  tolerance  of  the  patient. 

3 .  The  determination  of  the  carbon  dioxide  tension  of  the  alveolar  air. 

4.  The    determination    of    the    hydrogen-ion    concentration    of 

the  blood. 

It  must  be  at  once  apparent  that  the  development  of  acidosis  with 
its  excessive  acid  formation  will  tend  toward  a  change  in  the  reaction 
of  the  various  body  fluids,  particularly  the  blood.  However,  even  tn 
the  most  severe  acidosis  there  is  but  slight  alteration  in  the  reaction  of  the 
blood  since  the  ability  of  the  body  to  protect  itself  against  the  acid 
production  is  very  remarkable.  The  normal  reaction  of  the  blood 
is  slightly  alkaline.  If  there  be  but  slight  deviation  from  the  normal 
reaction,  health  rapidly  departs  and  death  may  ensue.  It  is  therefore 
of  first  importance  that  the  reaction  of  the  blood  be  kept  as  nearly 


308  PHYSIOLOGICAL   CHEMISTRY 

normal  as  possible.  In  fact  the  conditions  are  somewhat  similar  to 
those  which  surround  the  temperature  regulation  of  the  body.  Here 
again  the  body  attempts  to  maintain  a  normal  temperature.  A  given 
man  before  a  blast  furnace,  for  example,  shows  a  body  temperature  very 
similar  to  that  exhibited  by  the  same  man  in  the  ice  floes  of  the  north. 
Any  considerable  deviation  from  normal  in  the  temperature  of  our  body 
is  associated  with  failing  health  and  possible  death. 

The  popular  conception  of  water  is  that  of  a  fluid  which  is  neutral 
in  reaction.  As  a  matter  of  fact,  however,  in  ordinary  tap  water 
we  have  a  solution  more  alkaline  than  blood,  whereas,  distilled  water, 
which  is  our  standard  of  neutrality,  is  considerably  more  acid  than  is 
the  blood.  A  change  in  the  reaction  of  the  blood  equivalent  to  the 
very  slight  difference  between  the  reaction  of  tap  water  and  distilled 
water  would  be  fatal  to  the  organism. 

Just  a  word  in  review  as  to  the  physico-chemical  methods  of  ex- 
pressing the  reaction  of  a  solution.  A  neutral  solution  is,  of  course, 
one  which  contains  equal  numbers  of  hydrogen  and  hydroxyl  ions  while 
an  acid  solution  contains  an  excess  of  hydrogen  ions  and  an  alkaline 
solution  contains  an  excess  of  hydroxyl  ions.  The  extent  to  which  an 
acid  ionizes  or  liberates  hydrogen  ion  determines  the  efficiency  of 
that  acid  in  altering  the  reaction  of  a  solution.  Thus  tenth  normal 
solutions  of  hydrochloric  and  acetic  acids,  for  example,  each  contain 
the  same  amount  of  reacting  hydrogen  per  liter.  However,  91  per  cent 
of  the  hydrogen  of  the  hydrochloric  acid  dissociates  and  forms  hydrogen 
ion  whereas  only  1.3  per  cent  of  the  reacting  hydrogen  of  acetic  acid 
is  thus  dissociated.  Therefore,  the  decinormal  hydrochloric  acid  is 
70  times  as  strong  as  the  decinormal  acetic  acid. 

Pure  water  is  a  1/10,000,000  N  acid  and  a  1/10,000,000  N  alkali 
as  well.  If  we  take  a  normal  solution  of  an  acid  and  an  alkali  we  may 
dilute  each  until  the  hydrogen  and  hydroxyl  ion  concentrations  ap- 
proach that  of  water.  Instead  of  expressing  the  hydrogen  ion  con- 
centration of  water  as  1/10,000,000  N  it  is  customary  to  use  the  logarith- 
mic notation  and  express  it  as  io~7  N  or  rather  better  to  drop  the  io~ 
and  express  it  as  pH7  or  PH7  or  PH  —  7.  This  then  represents  the 
hydrogen  ion  concentration  of  a  neutral  solution.  Exponents  above  7 
indicate  alkaline  solutions  whereas  exponents  below  7  indicate  acid 
solutions. 
Thus  PHI  is  the  hydrogen  ion  concentration  of  N/io  acid. 

PH6  is  the  hydrogen  ion  concentration  of  N/ 1,000,000  acid. 

PH7  is  a  neutral  solution. 

PH8  is  the  hydroxyl  ion  concentration  of  N/ 1,000,000  alkali. 

PHi3.2  is  the  hydroxyl  ion  concentration  of  N/io  alkali. 


RESPIRATION    AND    ACIDOSIS  309 

The  reaction  of  blood  serum  is  about  Pn7-35-  The  maximum  varia- 
tions are  PH7  to  PH8.  The  former  value  (i.e.,  neutrality)  may  be 
reached  in  very  severe  acidosis  whereas  the  maximum  alkaline  value  of 
PH8  may  be  reached  by  alkali  administration.  The  average  value  for 
normal  urine  is  PH6  and  for  gastric  juice  PHi.77. 

Even  under  normal  conditions  the  human  body  is  continually 
forming  acids  as  a  result  of  oxidations  taking  place  in  intermediary 
metabolic  changes.  For  example,  the  sulphur  of  the  proteins  we  eat 
is  oxidized  to  sulphuric  acid,  whereas,  carbonic  acid  results  from  the 
transformation  not  only  of  proteins  but  of  fats  and  carbohydrates  as 
well.  Moreover,  there  are  small  amounts  of  various  organic  acids 
produced  and  ultimately  oxidized  with  the  formation  of  carbon  dioxide 
and  water,  although  a  certain  quantity  of  some  of  these  acids,  notably 
lactic  and  uric,  is  excreted  as  such. 

Let  us  examine  into  the  factors  which  the  blood  calls  to  its  aid 
in  maintaining  its  accustomed  reaction  in  the*  face  of  normal  or  ab- 
normal acid  production.  In  this  connection  we  must  consider  (i )  sodium 
bicarbonate  and  carbon  dioxide  which  are  present  in  proper  quantity 
to  yield  a  nearly  neutral  reaction,  (2)  the  acid  monosodium  hydrogen 
phosphate  and  the  alkaline  disodium  hydrogen  -phosphate  which  also 
are  present  in  proper  proportion  to  yield  a  similar  nearly  neutral  re- 
action as  that  formed  by  the  sodium  bicarbonate  and  carbon  dioxide, 
(3)  the  proteins  which  are  amphoteric  and,  therefore,  combine  with  acids 
or  alkalies  without  change  in  reaction.  The  carbonates  of  the  blood  are 
of  prime  importance  in  maintaining  the  constancy  of  reaction  and  have 
been  termed  the  "first  line  of  defense."  Carbon  dioxide  is  being  con- 
stantly formed  in  the  tissues.  This  is  carried  by  the  blood  to  the 
lungs  and  eliminated  in  respiration  as  carbon,  dioxide.  Every  24  hours 
an  average  adult  eliminates  in  this  way  acid  equivalent  to  several 
hundred  cubic  centimeters  of  concentrated  hydrochloric  acid.  Owing 
to  the  operation  of  laws  which  govern  the  reaction  of  solutions  of  weak 
acids  and  the  salts  of  such  acids,  the  blood  is  able  to  take  up  a  quantity 
of  the  acid  carbon  dioxide  without  undergoing  any  appreciable  change 
in  reaction.  In  this  way  large  amounts  of  acid  are  daily  eliminated 
from  the  body,  and  the  mechanism  is  so  nicely  adjusted  that  the 
organism  is  subjected  to  no  strain  of  any  sort. 

If  we  could  hold  our  breath  for  a  sufficiently  long  time  while  the 
circulation  continued  normally  we  would  finally  reach  a  point  where 
the  carbon  dioxide  concentration  would  be  the  same  in  the  alveolar 
air  as  in  the  blood  and  tissues.  The  process  of  respiration  lowers  the 
concentration  of  carbon  dioxide  in  the  lungs.  This  in  turn  permits  the 
entrance  of  carbon  dioxide  from  the  blood  into  the  alveoli  of  the  lungs 


310  PHYSIOLOGICAL    CHEMISTRY 

and  the  consequent  lowering  of  the  blood  carbon  dioxide  permits  the 
entrance  into  the  blood  of  carbon  dioxide  from  the  tissues  where  the 
concentration  of  carbon  dioxide  is  the  highest.  In  acidosis  the  carbon 
dioxide  concentration  of  the  alveolar  air  is  lowered  because  of  hyperpnea 
and  because  of  the  fact  that  the  power  of  the  blood  to  carry  carbon 
dioxide  has  been  lowered. 

When  acids  such  as  /3-hydroxy  butyric,  lactic  and  hydrochloric  are 
added  to  the  blood  they  react  with  the  sodium  bicarbonate  and  disodium 
phosphate  forming  a  sodium  salt  which  is  neutral  in  reactiom,  mono- 
sodium  phosphate  which  is  slightly  acid,  and  free  carbonic  acid.  The 
carbonic  acid  and  acid  phosphate  ionize  to  but  a  small  degree  and 
therefore  the  hydrogen  ion  concentration  of  the  blood  is  but  slightly 
altered.  We  have  here  a  very  efficient  factor  in  the  regulation  of 
blood  reaction  following  an  influx  of  acid  or  alkali.  The  regulatory 
mechanism  is  further  aided  by  the  rapid  elimination  of  the  acid  phos- 
phate and  carbonic  acid,  the  former  by  way  of  the  urine  and  the  latter 
by  way  of  the  lungs  in  the  form  of  carbon  dioxide.  The  following 
equations  represent  what  takes  place  when  an  excess  of  acid  (HC1) 
enters  the  blood. 

kidneys  lungs 

T  t 

NaHCOs  +  HC1  ->  NaCl  +  H2O  +  CO2 

kidneys  kidneys 

T  T 

Na2HPO4  +  HC1  -*  NaCl  +  NaH2PO4 

The  name  "buffer  substances"  has  been  given  to  the  sodium  phos- 
phate and  sodium  bicarbonate  of  the  blood  in  view  of  their  protective 
r61e'in  preventing  pronounced  changes  in  blood  reaction  after  acid  or 
alkali  introduction.  If  large  amounts  of  acids  are  continually  poured 
into  the  blood  these  buffer  substances  decrease  in  amount  and  finally 
when  the  body  can  no  longer  replace  the  destroyed  buffers  acidosis 
results.  In  fact  we  may  consider  that  acidosis  is  any  condition  in 
which  the  buffer  substances  of  the  blood  are  reduced  below  normal. 
Hence  acidosis  is  "lowering  of  the  alkali  reserve"  of  the  body.  When 
such  a  reduction  occurs  the  capacity  of  the  blood  to  transport  acids  is 
lowered.  We  have  seen  that  carbonic  acid  is  the  acid  most  abundantly 
produced  in  the  body  hence  the  "buffer"  depletion  lowers  the  power 
of  the  blood  to  carry  this  acid.  In  case  this  depletion  is  sufficiently 
pronounced  carbonic  acid  accumulates  in  the  tissues.  It  is  well  known 
that  the  respiratory  center  is  very  susceptible  to  acid  stimulation  such, 
e.g.,  as  that  afforded  by  carbonic  acid.  Hence  a  more  thorough  ventila- 
tion of  lungs  and  blood  results  and  the  more  rapid  removal  of  oarbon 
dioxide  prevents  its  further  accumulation  in  the  tissues.  This  hyperpnea 
resulting  from  a  stimulated  respiratory  center  is  one  of N  the  clinical 


RESPIRATION   AND   ACIDOSIS  311 

symptoms  of  acidosis.  Furthermore  one  of  the  laboratory  procedures 
for  establishing  the  extent  of  the  acidosis  is  the  estimation  of  the 
amount  of  the  reduction  in  the  carbon  dioxide  concentration  of  the 
alveolar  air  which  accompanies  the  hyperpnea.  This  indirect  index 
of  acidosis  may  be  determined  in  a  few  minutes.  (For  methods  see 
page  319.) 

A  rather  more  satisfactory  method  for  the  study  of  acidosis  is  the 
direct  determination  of  the  " buffer , value"  or  " alkali  reserve"  of  the 
blood.  This  consists  in  saturating  a  given  volume  of  blood  plasma  with 
carbon  dioxide  and  in  measuring  the  volume  of  carbon  dioxide  given  off 
from  this  blood  plasma  when  acid  is  added.  A  decrease  in  the  carbon 
dioxide  indicates  a  depletion  of  the  bicarbonate  of  the  blood  and  hence 
a  lowering  of  the  blood's  "buffer  value"  or  " alkali  reserve." 

The  alkali  reserve  may  also  be  determined  by  administering  sodium 
bicarbonate.  Normal  urine  is  acid  in  reaction.  When  bicarbonate  is 
given  to  a  normal  person  in  small  amount  the  reaction  of  the  urine 
becomes  alkaline.  In  acidosis,  however,  an  increased  amount  of  car- 
bonate is  necessary  to  produce  a  change  in  the  urinary  reaction.  The 
amount  of  alkali  needed  to  cause  the  urine  to  become  alkaline  is  an 
index  of  what  is  commonly  called  the  "tolerance  to  alkalies." 

Because  of  the  fact  that  it  varies  so  little  from  the  normal  under 
any  circumstances,  the  determination  of  the  hydrogen  ion  concentration 
of  the  blood  is  of  less  value  in  the  diagnosis  of  acidosis  than  either  the 
determination  of  the  "alkali  reserve"  of. the  blood,  the  "carbon  dioxide 
tension"  of  the  alveolar  air  or  the  "alkali  tolerance"  of  the  patient. 

METHODS 

i.  Alkali  Reserve. — Direct  Method,  (a)  Carbon  dioxide  ca- 
pacity of  the  plasma.  (Van  Slyke  and  Cullen.1) 

Principle. — The  plasma  from  oxalated  blood  is  shaken  in  a 
separatory  funnel  filled  with  an  air  mixture  whose  carbon  dioxide 
tension  approximates  that  of  normal  arterial  blood,  by  which  treatment 
it  combines  with  as  much  carbon  dioxide  as  it  is  able  to  hold  under 
normal  tension.  A  known  quantity  of  the  saturated  plasma  is  then 
acidified  within  a  suitable  pipette,  and  its  carbon  dioxide  is  liberated 
by  the  production  of  a  partial  vacuum.  The  liberated  carbon  dioxide 
is  then  placed  under  atmospheric  pressure,  its  volume  carefully 
measured,  and  the  volume  corresponding  to  100  c.c.  of  plasma 
calculated. 

Apparatus. — The  apparatus2  used  in  the  estimation  of  the  carbon 

1  Van  Slyke  &  Cullen:  Jour.  Biol.  Chem.,  30,  289,  1917;  Van  Slyke:  Jour.  Biol.  Chem.t 
30,  347,  1917- 

2  The  apparatus  is  manufactured  by  the  Emil  Greiner  Company,  55  Fulton  Street, 
New  York. 


312 


PHYSIOLOGICAL   CHEMISTRY 


Position  1 


dioxide  content  of  the  plasma  is  illustrated  in  Fig.  100.  It  is  made 
of  strong  glass  in  order  to  stand  the  weight  of  mercury  without  danger 
of  breaking,  and  is  held  in  a  strong  screw  clamp  the  jaws  of  which  are 

lined  with  thick  pads  of  rubber. 
In  order  to  prevent  accidental 
slipping  of  the  apparatus  from 
the  clamp,  an  iron  rod  of  6  or 
8  mm.  diameter  should  be  so 
arranged  as  to  project  under 
cock/  between  c  and  d. 

Three  hooks  or  rings  at  the 
levels  i,  2,  and  3  serve  to  hold 
the  levelling  bulb  at  different 
stages  of  the  analysis.  The 
bulb  is  connected  with  the  bot- 
tom of  the  apparatus  by  a 
heavy  walled  rubber  tube. 

It  is  necessary,  of  course, 
that  both  stop  cocks  should  be 
properly  greased  and  air  tight, 
and  it  is  also  essential  that  they 
(especially  /)  shall  be  held  in 


i  mm.  bore 


Position  2  V-/50CC 

3  mm  bore 


Supporting 
Rod 


Paraffin  Oil- 


Position  3 
is  eo  cm  below 
position  z 


FIG.  ioo.- VAN  SLYKE  CARBON  DIOXIDE  AP-          FIG.    I°I--TUBE   USED    IN  COL- 
PARATUS.     (Journal  Biological  Chemistry,  3°,  **9,    ACTING   BLOOD     (Journal  Biological 
30  347,  TOT*.}  Chemistry,  30,  289,  1917.) 


in 

w 

1 

m 

RESPIRATION    AND    ACIDOSIS  313 

place  so  that  they  cannot  be  forced  out  by  pressure  of  the  mercury. 
Rubber  bands  may  be  used  for  this  purpose  but  it  is  suggested  that 
elastic  cords  of  fine  wire  spirals,  applied  in  the  same  manner  as 
rubber  bands,  are  stronger  and  more  durable. 

After  a  determination  has  been  finished,  the  levelling  bulb  is  lowered 
without  opening  the  upper  cock,  and  most  of  the  mercury  is  withdrawn 
from  the  pipette  through  c.  The  water  solution  from  d  is  readmitted 
and  the  levelling  bulb  being  raised  to  position  i,  the  water  solution, 
together  with  a  little  mercury,  is  forced  out  of  the  apparatus  through  a.1 

Procedure. — Drawing  the  blood.2  About  six  or  seven  c.c.  of  venous  blood 
are  aspirated  into  a  centrifuge  tube  (see  Fig.  101)  which  contains  a  little  powdered 


FIG,  102. — SEPARATORY  FUNNEL  USED  IN  SATURATING  BLOOD  PLASMA  WITH  CARBON 
DIOXIDE.     (Journal  Biological  Chemistry,  30,  289,  1917.) 

potassium  oxalate  and  some  paraffin  oil.  The  tube  is  subjected  to  a  minimum 
of  agitation  after  the  blood  is  in  it.  The  slight  amount  of  agitation  necessary 
to  assure  mixture  with  the  oxalate  is  accomplished  by  stirring  with  the  inlet 
tube,  rather  than  by  inverting  or  shaking.  The  tube  and  contents  are  then 
centrifuged. 

Saturation  of  Plasma  with  Carbon  Dioxide. — After  centrifugation  about 
3  c.c.  of  the  plasma3  are  transferred  to  a  300  c.c.  separatory  funnel,  arranged 
as  in  Fig.  102,  and  the  air  within  the  funnel  is  displaced  by  either  alveolar  air 
from  the  lungs  of  the  operator  or  a  5.5  per  cent  carbon  dioxide-air  mixture 
from  a  tank.  In  either  case  the  gas  mixture  must  be  passed  over  moist  glass 
beads  before  it  enters  the  funnel. 

When  alveolar  air  is  used  the  operator,  without  inspiring  more  deeply  than 
normal,  expires  as  quickly  and  as  completely  as  possible  through  the  glass  beads 

1  It  is  well  to  have  a  funnel  draining  into  a  special  vessel  to  catch  the  water  residues 
and  mercury  overflow  from  a.    A  considerable  amount  of  mercury  is  thus  regained  if 
many  analyses  are  run.     It  requires  only  straining  through  cloth  or  chamois  skin  to  prepare 
it  for  use  again. 

2  For  at  least  an  hour  before  the  blood  is  drawn  the  subject  should  avoid  vigorous 
muscular  exertion  as  this,  presumably  because  of  the  lactic  acid  formed  lowers  the  bi- 
carbonate of  the  blood.     (Christiansen,  Douglas  &  Haldane:  /.  Physiol.,  48,  246,  1914; 
Morawitz  &  Walker:  Biochem.  Zeit.,  60,  395,  1914.) 

3  If  it  is  desired  to  keep  the  plasma  for  the  estimation  of  carbon  dioxide  at  a  later  time 
it  should  be  transferred  to  a  paraffined  tube,  covered  with  a  layer  of  paraffin  oil,  stoppered 
and  kept  cold;  under  which  conditions  it  is  claimed  that,  if  sterile,  it  may  be  kept  for  over 
a  week  without  alteration  of  its  carbon  dioxide  capacity. 


314  PHYSIOLOGICAL    CHEMISTRY 

and  separately  funnel.  The  stopper  of  the  funnel  should  be  inserted  just  before 
the  expiration  is  finished,  so  that  there  is  no  opportunity  for  air  to  be  drawn 
back  into  the  funnel.  In  order  to  saturate  the  plasma  the  separatory  funnel 
is  turned  end  over  end  for  2  minutes,  the  plasma  being  distributed  in  a  thin 
layer  as  completely  over  the  surface  of  the  funnel's  ulterior  as  is  possible.  After 
saturation  is  completed  the  funnel  is  placed  upright  and  allowed  to  stand  for  a 
few  minutes  until  the  fluid  has  drained  from  the  walls  and  gathered  in  the  con- 
tracted space  at  the  bottom  of  the  funnel. 

Determination  of  Carbon  Dioxide. — A  sample  of  i  c.c.  (or  0.5  c.c.  in  case  the 
amount  of  plasma  available  is  very  small)  accurately  pipetted,  is  allowed  to  run 
into  the  cup  b  in  the  apparatus  represented  in  Fig.  100,  the  tip  of  the  pipette 
remaining  below  the  suface  of  the  plasma  as  it  is  added.  The  cup  should  have 
been  previously  washed  out  with  carbonate-free  ammonia,  and  together  with 
the  entire  apparatus  should  have  been  filled  with  mercury  to  the  top  of  the  capil- 
lary tube  by  placing  the  levelling  bulb  of  mercury  in  position  i. 

With  the  mercury  bulb  at  position  2  and  the  cock  /  hi  the  position  shown  in 
the  figure  the  plasma  is  admitted  from  the  cup  into  the  50  c.c.  chamber,  leaving 
just  enough  above  the  cock  e  to  fill  the  capillary  so  that  no  air  is  introduced 
when  the  next  solution  is  added.  The  cup  is  washed  with  two  portions  of  about 
0.5  c.c.  of  water,  each  portion  being  added  to  the  pipette  in  turn.  A  small 
drop1  of  caprylic  alcohol  is  then  added  to  the  cup  and  is  permitted  to  flow 
entirly  into  the  capillary  above  e.  Finally  0.5  c.c.  of  5  per  cent  sulphuric  acid 
is  run  in. 

It  is  not  necessary  that  exactly  i  c.c.  of  wash  water  and  0.5  c.c.  of  acid  shall 
be  taken,  but  the  total  volume  of  the  water  solution  introduced  must  extend 
exactly  to  the  2.5  c.c.  mark  on  the  apparatus,  if  the  table  on  page  330  is  to  be 
used. 

If  the  amount  of  plasma  available  is  small  a  little  more  than  0.5  c.c.  are 
saturated  in  a  50  c.c.  funnel,  and  exactly  0.5  c.c.  used  for  the  estimation  of 
carbon  dioxide.  In  this  case  the  volume  of  distilled  water  and  acid  used  to 
wash  the  plasma  into  the  apparatus  is  halved,  so  that  the  total  volume  of  water 
solution  introduced  is  only  1.25  c.c.,  and  in  the  calculation  the  observed  volume 
of  gas  is  multiplied  by  2. 

After  the  acid  has  been  added  a  drop  of  mercury  is  placed  in  b  and  allowed 
to  run  down  the  capillary  as  far  as  the  cock  hi  order  to  seal  the  latter.  Whatever 
excess  of  sulphuric  acid  remains  in  the  cup  is  washed  out  with  a  little  water. 

The  mercury  bulb  is  now  lowered  and  hung  at  position  3  and  the  mercury 
in  the  pipette  is  allowed  to  run  down  to  the  50  c.c.  mark,  producing  a  Torricellian 
vacuum  in  the  apparatus.  When  the  mercury  (not  the  water)  meniscus  has 
fallen  to  the  50  c.c.  mark  the  lower  cock  is  closed  and  the  pipette  is  removed 
from  the  clamp.  Equilibrium  of  the  carbon  dioxide  between  the  2.5  c.c.  of  water 
solution  and  the  47.5  c.c.  of  free  space  in  the  apparatus  is  obtained  by  turning 
the  pipette  upside  down  fifteen  or  more  times,  thus  thoroughly  agitating  the  con- 
tents. The  pipette  is  then  replaced  in  the  clamp. 

By  turning  the  cock  /  the  water  solution  is  now  allowed  to  flow  from  the 
pipette  completely  into  d  without,  however,  allowing  any  of  the  gas  to  follow 

1  It  is  desirable  to  keep  the  amount  of  caprylic  alcohol  small,  as  larger  amounts  may 
appreciably  increase  results.  With  plasma  0.02  c.c.  is  sufficient  to  prevent  foaming  and 
is  measured  most  conveniently  from  a  burette  made  by  fusing  a  capillary  stopcock  to  a 
pipette  graduated  into  o.oi  c.c.  divisions. 


RESPIRATION    AND    ACIDOSIS 


315 


it.  The  levelling  bulb  is  then  raised  hi  the  left  hand  while  with  the  right  the 
cock  is  turned  so  as  to  connect  the  pipette  with  c.  The  mercury  flowing  in  from 
c  fills  the  body  of  the  pipette,  and  as  much  of  the  calibrated  stem  at  the  top  as 
is  not  occupied  by  the  gas  extracted  from  the  solution.  A  few  hundredths  of 
a  c.c.  of  water  which  could  not  be  completely  drained  into  d  float  on  top  of  the 
mercury  in  the  pipette,  but  the  error  caused  by  reabsorption  of  carbon  dioxide 
into  this  small  volume  of  water  is  negligible  if  the  reading  is  made  at  once.  The 
mercury  bulb  is  placed  at  such  a  level  that  the  gas  in  the  pipette  is  under  atmos- 
pheric pressure1  and  the  volume  of  the  gas  is  read  on  the  scale. 

Calculation. — By  means  of  the  table  on  page  316  the  readings  on  the  apparatus 
can  be  directly  transposed  into  c.c.  of  carbon  dioxide  chemically  bound  by  100 
c.c.  of  plasma.  The  barometer  reading  and  room  temperature  are  taken  at 
the  time  of  the  determination.  For  convenience  hi  the  calculation  values  are 

B 
given  below  for  the  ratio  ->-  over  the  range  usually  encountered. 


Barometer 

B 

760 

Barometer 

B 

760 

732 

0.963 

756 

0-995 

734 
736 

0.966 
0.968 

760 

0.997 

.000 

738 

0.971 

762 

.003 

740 

0.974 

764 

.006 

742 

0.976 

766 

.008 

744 

0.979 

768 

.on 

746 

0.981 

770 

.013 

748 

0.984 

772 

.016 

750 

0.987 

774 

.018 

752 

0.989 

776 

1.  021 

754 

0.992 

778 

I.O24 

In  case  the  volume  of  plasma  taken  for  estimation  of  carbon  dioxide  content 
was  0.5  c.c.  the  observed  volume  of  gas  is  multiplied  by  2  before  it  is  used  to 
calculate  the  volume  per  cent  of  carbon  dioxide  bound. 

Interpretation. — The  carbon  dioxide  capacity  of  the  plasma  as 
determined  by  this  method  appears  to  indicate  not  only  the  alkaline 
reserve  of  the  blood  but  also  that  of  the  entire  body.  The  average 
normal  value  for  man  is  65  volume  per  cent  of  carbon  dioxide.  The 
table,  page  317,  shows  the  range  of  results  obtained  with  normal  and 
pathological  plasma,  as  well  as  the  relationship  of  the  plasma  bi- 
carbonate to  acid  excretion,  alkali  tolerance,  and  alveolar  carbon 
dioxide  tension. 

1  In  order  to  have  the  column  in  the  pipette  exactly  balanced  by  that  outside,  the  surface 
of  the  mercury  in  the  levelling  bulb  should  be  raised  until  it  is  level  with  the  mercury 
meniscus  in  the  pipette,  and  then,  for  entire  accuracy,  raised  above  the  latter  meniscus 
by  a  distance  equal  to  Y\±  the  height  of  the  column  of  water  above  the  mercury  in  the 
pipette.  As  the  water  column  is  as  a  rule,  only  about  10  mm.  high,  the  correction  that 
has  to  be  estimated  is  less  than  i  mm.  of  mercury,  i.  e.,  the  entire  correction  for  the  water 
column  is  not  enough  to  influence  results  appreciably. 


PHYSIOLOGICAL    CHEMISTRY 


TABLE  FOR  CALCULATION  OF  CARBON  DIOXIDE  COMBINING  POWER 

OF  PLASM  A * 


j   C.c.  of  CO2  reduced  to  o° 
Observed         760  mm.  bound  as  bicar- 


Observed 


C.c.  of  CO2  reduced  to  o° 
760  mm.  bound  as  blear- 


v  vr*»     £C4.o 

B 

*  Tfo 

uuiiaic   ujr   AUU  v».v.  ui 

plasma 

vui.  ga.& 

B 

X76o 

UUUO.LC   u_y  xuu  c.v<  UJL 

plasma 

15° 

20°        25° 

30° 

15°           20°           25° 

30° 

O.2O 

9.1        99 

10.7      n.  8 

0.60         47.7 

48  .  i     48  .  5     48  .  6 

I 

10.  I 

10.9 

11.7 

12.6 

i         48.7 

49.0     49.4     49.5 

2 

II.  O 

ii.  8 

12.6 

13.5 

2 

49-7 

50.0     50.4 

50-4 

3 

12.0 

12.8 

13-6      14.3 

3 

50.7 

Si.o  |  51.3 

51-4 

4 

13  o 

13  7 

14  5 

15   2 

4 

Si  6 

5i  9      52.2 

52.3 

5 

13-9 

14.7 

15-5 

16.1 

5 

52.6 

52.8      53-2 

53  2 

6 

14.9 

15.7 

16.4 

17.0 

•        6         53-6 

53-8      54-1 

54-1 

7 

15-9 

16.6 

17.4 

18.0 

7         54.5 

54-8      55  i 

55-1 

8 

16.8 

17.6 

18.3 

18-9 

8       !  55  5 

55-7      56.o 

56.0 

9 

17-8 

18.5 

19.2 

19.8 

9 

56.5 

56.7     57-0 

56.9 

0.30 

18.8 

19-5 

20.2, 

20.8 

0.70 

57-4 

57-6     57-9 

57-9 

i 

19.7 

20.4 

21.  1 

21.7 

i 

58.4 

58.6 

58.9 

58.8 

2 

20.7 

21.4 

22.1 

22.6 

2 

59-4 

59-5 

59-8 

59  7 

3 

21.7 

22.3 

23.0 

23.5 

3 

60.3 

60.5     60.7 

60.6 

4 

22.6 

23-3 

24.0 

24-5 

4 

6i-3 

61.4  !  61.7 

61.6 

5 

23.6 

24.2 

24-9 

25-4 

5 

62.3 

62.4 

62.6 

62.5 

6 

24.6 

25.2 

25.8 

26.3 

6 

63.2 

63-3 

63.6 

63.4 

7 

25  5 

26.2 

26.8 

27.3 

7 

64.2 

64.3 

64.5 

64.3 

8 

26.5 

27.1 

27.7 

28.2 

8 

65.2 

65.3 

65-5 

65-3 

9 

27-5 

28.1 

28.7 

29.1 

9 

66.1 

66.2 

66.4 

66.2 

0.40 

28.4 

29.0 

29.6 

30.0 

0.80 

67.1 

67.2 

67-3 

67.1 

i 

29.4 

30.0 

30:5 

31.0 

i 

68.1 

68.1 

68.3 

68.0 

2 

30.3 

30.9 

3L5 

3i  9 

2 

69.0 

69.1 

69.2 

69.0 

3 

31-3 

31-9 

32.4 

32.8 

3 

70.0 

70.0 

70.2 

69.9 

4 

32.3 

32.8 

33-4 

33-8 

4 

71.0 

71.0 

71.1 

70.8 

5 

33  2 

33-8 

34.3 

34.7 

5 

71.9 

72.0 

72.1 

71.8 

6 

34-2 

34-7 

35-3 

35-6 

6 

72.9 

72.9 

73-0 

72.7 

7 

35-2 

35-7 

36.2 

36.5 

7 

73  9 

73-9 

74-0 

73  6 

8 

36.1 

36.6 

37.2 

37.4 

8 

74-8 

74-8 

74-9 

74  5 

9 

37-i 

37-6 

38.1 

38.4 

9 

75-8 

75-8 

75.8 

75-4 

0.50 

38-1 

38.5 

39-0 

39  3 

0.90 

76.8 

76.7 

76.8 

76.4 

i 

39-1 

39  5 

40.0 

40.3 

i 

77-8 

77-7 

77-7 

77-3 

2 

40.0 

40.4 

40-9 

41.2 

2 

78.7 

78.8 

78.7 

78.2 

3 

41.0 

41.4 

41.9 

42.1 

3 

79.7 

79-6 

79  6 

79-2 

4 

42.0 

42.4 

42.8 

43-0 

4 

80.7 

80.5 

80.6 

80.  i 

5 

42-9 

43-3 

43-8 

43-9 

5 

81.6 

81.5     81.5 

81.0 

6 

43-9 

44-3 

44-7 

44.9 

6 

82.6 

82.5     82.4 

82.0 

7 

44-9 

45-3 

45-7 

45.8 

7 

83.6 

83.4     83.4 

82.9 

8 

"45.8 

46.2 

46.6 

46.7 

8 

84.5 

84.4 

84.3 

83.8 

9 

46.8 

47-1 

47-5 

47.6 

9 

85-5 

85-3 

85.2 

84.8 

0.60 

47-7 

48.1 

48.5 

48.6 

1.  00 

86.5 

86.2 

86.2 

85-7 

1  The  temperature  figures  at  the  heads  of  columns  represent  the  room  temperature 
at  which  the  samples  of  plasma  are  saturated  with  alveolar  carbon  dioxide  and  analyzed. 
It  is  assumed  that  both  operations  are  performed  at  the  same  temperature.  The^  figures 
have  been  so  calculated  that,  regardless  of  the  room  temperature  at  which  saturation  and 
analysis  are  performed,  the  table  gives  the  volume  (reduced  to  o°,  760  mm.)  ^of  carbon 
dioxide  that  100  c.c.  of  plasma  are  capable  of  binding  when  saturated  at  20  with  carbon 
dioxide  at  approximately  41  mm.  tension.  If  the  figures  in  the  table  are  multiplied  by 
0.94  they  give,  within  i  or  2  per  cent  of  the  carbon  dioxide  bound  at  37°. 


RESPIRATION   AND    ACIDOSIS 


317 


318  PHYSIOLOGICAL    CHEMISTRY 

(b)  Plasma  Bicarbonate  (Titration  Method)  Van  Slyke,  Stillman 
and  Cullen.1 — Principle. — Plasma  is  treated  with  an  excess  of  standard 
acid  which  is  titrated  back  with  standard  alkali  under  carefully  stand- 
ardized conditions. 

Procedure. — In  drawing  and  centrifugating  the  blood  the  precautions  outlined 
by  Van  Slyke  and  Cullen  for  preventing  loss  or  accumulation  of  CO  2  and  consequent 
change  in  the  distribution  of  bicarbonate  between  corpuscles  and  plasma,  are  to  be 
observed.  Oxalate  plasma  is  used.  Up  to  the  beginning  of  the  analysis,  the  blood 
and  plasma  are  handled  exactly  as  described  for  the  CO2  method.  Pipette  2  c.c, 
of  plasma  into  a  150-200  c.c.  round-bottomed  flask  and  add  5  c.c.  of  0.02  N  HC1 
(this  is  about  2  c.c.  in  excess  of  the  bicarbonate  normally  present).  Shake  the 
flask  vigorously  with  a  rotary  motion  so  that  the  solution  is  whirled  in  a  thin  layer 
about  the  inner  wall.  One  minute  of  this  treatment  is  sufficient  completely  to 
remove  the-CO2  set  free  by  the  acid.  Pour  the  solution  as  completely  as  possible 
into  a  50  c.c.  Erlenmeyer  flask  and  rinse  the  walls  of  the  larger  flask  with  20  c.c. 
of  H2O  measured  within  i  c.c.  in  a  cylinder,  using  a  third  for  each  of  3  washings. 
Add  0.3  c.c.  of  o.i  per  cent  solution  of  neutral  red  in  50  per  cent  alcohol.  Run  in 
0.02  N  carbonate- free  NaOH  from  a  burette  (preferably  but  not  necessarily  a 
"microburette")  until  the  color  of  the  solution  matches  that  of  29  c.c.  of  a  standard 
phosphate  solution  of  pff  y.42  contained  in  a  similar  50  c.c.  flask.  In  place  of 
neutral  red,  0.3  c.c.  of  a  0.04  per  cent  solution  of  phenolsulphonephthalein  may  be 
used  and  gives  an  end  point  slightly  more  easy  to  distinguish.  When  it  is  used, 
however,  the  standard  phosphate  solution  must  be  of  p# 7.2  instead  of  7.4.  With 
both  indicators,  a  peculiar  phenomenon  occurs  as  the  end  point  is  approached. 
Each  drop  appears  to  change  the  color  past  the  end  point,  but  within  a  few  seconds 
the  color  shifts  back  and  it  is  seen  that  at  least  another  drop  is  needed.  Con- 
sequently, the  final  color  comparison  should  not  be  made  until  at  least  30  seconds 
after  the  last  drop  of  0.02  N  NaOH  has  been  added.  It  is  better,  particularly  with 
neutral  red,  to  overrun  the  end  point  by  a  drop,  rather  than  stop  short  of  it  when 
in  doubt.  In  calculating  the  results  the  c.c.  of  0.02  N  NaOH  used  in  the  titration 
is  subtracted  from  the  c.c.  required  to  neutralize  to  the  same  indicator  5  c.c.  of  the 
0.02  N  HC1  used.  The  number  is  approximately  5  but  usually  varies  from  it 
slightly  because  of  difference  in  factors  of  acid  and  alkali  and  because  of  the  calibra- 
tion error  of  the  5  c.c.  pipette  used  in  measuring  the  acid.  The  maximum  accuracy 
is  obtained  by  performing  a  preliminary  titration  on  5  c.c.  of  the  acid  plus  20  c.c.  of 
distilled  water,  using  the  same  pipette,  indicator,  and  end  point  as  in  the  plasma 
titration.  The  titration  result  represents  c.c.  of  o.oi  M  NaHCO3  per  c.c.  of  plasma 
and  it  is  transformed  into  terms  of  molecular  concentration  of  NaHCOa  by  merely 
dividing  by  100.  If  the  NaHCOs  molecular  concentration  is  multiplied  by  2240  or 
the  number  of  c.c.  of  0.02  N  HC1  used  in  the  titration  by  22.4,  the  volume  per  cent 
of  bicarbonate  CO2  in  the  plasma  is  obtained  and  the  results  can  thus  be  compared 

1  Van  Slyke,  Stillman  and  Cullen:  Jour.  Biol.  Chem.,  38,  167,  1919. 

2  To  obtain  the  standard  solutions  of  p#7.2  and  7.4  proceed  as  follows:  for  p#7.2  mix 
50  c.c.  of  0.2  M  KH2PO4(27.23  g.  per  L.)  and  35  c.c.  of  0.2  N  NaOH  and  dilute  to  200  c.c.; 
for  p#  7.4,  mitf  50  c.c.  of  0.2  M  KH2PO4  and  39.5  c.c.  of  0.2  N  NaOH  and  dilute  to  200  c.c. 
To  prepare  the  solutions  by  Sorenson's  method,  dissolve  6.89  g.  Na2HPO4  and  247  g.  of 
KH2PO4  in  H2O  and  dilute  to  i  liter  for  p#y.2;  for  P#y.4  the  amounts  are  7.72  g.  and  1.67 
g.,  respectively  (if  Na2HPO4-2H2O  is  used  instead  of  the  anhydrous  salt,  the  amounts  are 
increased  to  8.66  and  9.67  g.).     Both  salts  prepared  especially  for  this  purpose  may  be 
obtained  from  Merck  &  Co. 


RESPIRATION    AND    ACIDOSIS  319 

with  those  obtained  by  the  CO2  method.  The  standard  0.02  N  NaOH  must  be 
protected  from  atmospheric  CO2  and  kept  in  paraffined  bottles  to  prevent  solution 
of  alkali  from  the  glass.  The  burette  should  be  filled  with  fresh  solution  each 
day.  The  carbonate-free  solution  is  made  by  dissolving  the  NaOH  in  an  equal 
volume  of  H2O.  On  standing  the  Na2CO?  settles  to  the  bottom.  5.5  c.c.  of  the 
clear  supernatant  solution  is  diluted  to  5  L.  and  standardized  by  titration  with 
neutral  red  against  0.02  N  HC1.  It  is  preferable  to  run  the  acid  into  the  alkali  as 
the  color  change  occurs  without  the  time  lag  observed  when  alkali  is  added  to  acid. 

A  micro-titration  method  is  also  described  in  which  the  determination  can  be 
made  with  0.4  c.c.  of  plasma.  If  special  care  is  taken  in  the  calibration  of  pipettes 
and  in  the  control  of  the  0.004  N  NaOH  used  results  nearly  and  perhaps  quite  as 
accurate  as  in  the  larger  titration  appear  attainable.1 

Interpretation. — The  results  agree  closely  with  those  of  the  CO2  capacity  method 
over  the  range  of  bicarbonate  concentrations  (0.03  to  o.oi  M)  ordinarily  encoun- 
tered in  man,  even  in  severe  acidosis.  Below  this  range  the  titration  continues  to 
give  accurate  results,  while  the  CO2  capacity  method  gives  somewhat  higher 
values.  For  clinical  and  most  experimental  purposes,  however,  it  appears  that  the 
two  methods  give  so  nearly  identical  results  that  they  may  be  used  interchangeably. 

2.  Alkali  Reserve. — Indirect  Method.  Alveolar  Carbon  Dioxide 
Tension.  Fridericia's  Method.2 

Principle. — The  method  of  determination  is  based  upon  the  absorp- 
tion, by  means  of  potassium  hydroxide,  of  the  carbon  dioxide  from  a 
known  amount  of  alveolar  air.  The  apparatus  is  so  graduated  that 
the  decrease  in  volume  may  be  read  in  per  cent. 

Procedure.— The  subject  must  sit  quietly  in  a  chair  and  breathe  naturally,3 
holding  the  apparatus  (shown  in  Fig.  103)  in  front  of  him  with  the  cock  a 
open  and  b  in  a  position  connecting  x  with  y.  After  taking  a  normal  inspi- 
ration he  places  the  mouthpiece  m  into  his  mouth  and  blows  as  hard  and  as 
quickly  as  possible  through  the  apparatus  thus  washing  it  out  and  leaving  it 
filled  with  alveolar  air.  The  cock  a  is  at  once  closed  and  the  whole  apparatus 
is  immersed  in  water  for  5  minutes.  By  this  means  the  alveolar  air  in  x  and  y 
is  cooled  to  a  temperature  which  remains  constant  throughout  the  experiment, 

1  Testing  Standard  0.02  N  NaOH  for  Carbonate.— The  solutions  should  be  made  up 
using  only  boiled  water,  be  kept  in  paraffine-lined  bottles,  and  be  protected  from  atmos- 
pheric CO2  by  soda-lime  tubes.  They  should  be  tested  for  carbonate  as  follows: 

To  5  c.c.  of  0.02  N  HC1  in  a  200  c.c.  round  flask,  add  from  a  freshly  filled  burette  about 
4.8  c.c.  of  the  0.02  N  NaOH  to  be  tested,  0.3  c.c.  of  neutral  red  solution.  The  mixture 
should  be  strongly  acid  to  the  indicator.  The  solution  is  rotated  for  one  minute  in  the 
flask  to  permit  the  escape  of  CO2,  and  is  then  transferred  to  a  50  c.c.  Erlenmeyer  flask 
and  titrated  as  in  plasma  analyses,  the  total  amount  of  0.02  N  NaOH  required  to  give  the 
end  point  being  noted. 

A  duplicate  titration  is  performed  in  the  same  way  except  that  there  is  no  agitation 
to  remove  carbon  dioxide,  the  0.02  N  HC1  plus  20  c.c.  of  water  being  placed  directly  in  the 
50  c.c.  Erlenmeyer  flask,  and  the  0.02  N  NaOH  being  added  with  a  minimum  of  stirring. 

If  there  is  no  carbonate  in  the  standard  NaOH  solution  the  two  titrations  give  identical 
results.  The  difference  should  preferably  not  exceed  o.i  c.c.,  and  if  it  exceeds  0.2  c.c.  the 
alkali  should  not  be  used. 

2Fridericia:  Hospitalstidende,  Copenhagen,  57,  585,  1914;  Poulton:  Brit.  Med.  'Jour., 
2,  392,  1915. 

3  It  is  especially  important  to  caution  the  subject  against  the  very  natural  inclination 
to  take  an  abnormally  deep  inspiration  just  before  blowing  through  the  apparatus,  and 
also  to  see  that,  in  seeking  to  avoid  this  fault,  the  breath  is  not  held  just  before  the  sample 
is  taken. 


320 


PHYSIOLOGICAL   CHEMISTRY 


m 


and  the  contraction  in  volume  causes  the  alveolar  air  in  the  lower  part  of  y  to 
be  drawn  back  into  x.1  At  the  end  of  5  minutes  the  cock  b  is  turned  so  as  to 
connect  y  with  c,  thus  closing  x  which  then  contains  exactly  100  c.c.  of  alveolar 
air  at  atmospheric  pressure  and  at  the  temperature  of  the  water  in  which  the 
apparatus  is  immersed,  this  temperature  remaining  constant  throughout  the 
determination.  The  apparatus  is  removed  from  the  water,  the  tube  c  is  placed 
beneath  the  surface  of  some  10  per  cent  sodium  hydroxide  solution,  some  of 
the  alkali  is  drawn  up  into  y,  the  apparatus  is  held  in  such  a  position  that  y  is 
rather  depressed  in  order  to  prevent  the  escape  of 
small  bubbles  of  gas  from  x,  the  cock  is  turned  so  as 
to  connect  y  with  x,  and  some  of  the  alkali  is  forced 
into  x.  The  cock  b  is  at  once  turned,  closing  x  and 
connecting  y  with  c  through  which  the  remainder  of 
the  alkali  is  allowed  to  flow.  The  apparatus  is  inverted 
several  times  during  the  course  of  half  a  minute  which  is 
sufficient  time  for  the  absorption  of  all  the  carbon 
dioxide.  It  is  then  returned  to  the  water  which  rises 
through  c  into  y,  after  which  b  is  turned  to  connect  y 
and  x  and  the  whole  is  allowed  to  remain  for  5  minutes 
to  again  equalize  the  temperature.  It  is  then  raised 
rapidly  until  the  water  in  the  graduated  portion  of  x  is 
at  the  same  level  as  the  water  outside  the  apparatus, 
i.e.,  when  the  gas  within  the  tube  x  is  under  atmos- 
pheric pressure. 

Calculation. — The  reading  of  the  bottom  of  the 
meniscus  of  the  fluid  in  x  is  taken  and  represents, 
without  any  further  calculation  or  correction,  the  per- 
centage of  carbon  dioxide  in  the  alveolar  air.  If  it  is 
desired  to  express  this  percentage  as  the  partial  pressure 
of  CO 2  in  millimeters  of  mercury2  it  is  multiplied  by  a 
figure  40  mm.  less  than  the  prevailing  barometric  pres- 
sure ;  e.g.,  if  the  reading  of  the  apparatus  is  5.5  then  the  calculation  will  be 
as  follows:  5.5  per  cent  CO2  or  0.055  X  (760  —  40).  This  40  mm.  is  the 
tension  of  water  vapor  in  the  lungs  at  body  temperature.  It  is  sufficient  for 
clinical  purposes  to  use  the  mean  barometric  pressure  of  the  locality,  neglect- 
ng  the  daily  variations. 

Interpretation. — The  sample  of  air  obtained  by  this  method  (if  prop- 
erly taken)  represents  more  nearly  air  whose  C02  tension  is  the  same 
as  that  of  arterial  blood,  i.e.,  true  alveolar  air,  than  does  air  obtained 
by  "  rebreathing. "  The  results  obtained  by  this  method,  then,  are 
from  5  to  10  per  cent  lower  than  those  obtained  by  the  Marriott 
method  below.  The  average  normal  value  for  men3  is  about  5.5 
volumes  per  cent  of  carbon  dioxide.  In  women  and  children  the 
normal  value  is  somewhat  lower.  In  acidosis  the  carbon  dioxide  falls 

1  Any  diffusion  with  the  outside  air  at  the  top  of  y  will  not  reach  to  the  bottom  of  the 
tube  owing  to  its  length. 

2  Henderson  and  Morriss:  Jour.  Biol.  Chem.,  31,  217,  1917. 

3  Beddard,  Pembrey,  and  Spriggs:  Brit.  Med.  Jour.    2,  389,  1915. 


FIG.  103. — FRIDERICIA 
APPARATUS. 


RESPIRATION    AND    ACIDOSIS  321 

and  in  diabetic  coma  may  go  as  low  as  i  or  2  per  cent.  A  value  of 
2  per  cent  means  that  coma  may  supervene  within  24  hours.  A  value 
of  3  per  cent  or  4  per  cent  is  less  dangerous;  in  the  worst  event  coma 
will  not  come  on  for  at  least  two  or  three  days.  For  detailed  data  as 
to  alveolar  carbon  dioxide  tension  under  different  conditions  see  table 
on  page  317. 

3.  Alkali  Reserve.  Indirect  Method.  Alveolar  Carbon  Dioxide  Tension 
Marriott's  Method.^ — While  this  method  is  open  to  criticism  because  of  the  liability 
of  error  in  the  collection  of  the  sample  and,  more  fundamentally,  because  of  various 
factors  (psychical,  etc.)  other  than  acidosis  which  may  influence  the  carbon  dioxide 
tension,  nevertheless,  it  is  of  considerable  value  and  has  been  rather  widely  adopted 
for  clinical  use. 

Principle. — By  rebreathing  air  under  certain  definite  conditions  a  sample  is 
obtained  whose  carbon  dioxide  tension  is  virtually  that  of  venous  blood.  The 
method  of  analysis  of  this  sample  depends  on  the  fact  that  if  a  current  of  air  con- 
taining carbon  dioxide  is  passed  through  a  solution  of  sodium  carbonate  or  bi- 
carbonate until  the  solution  is  saturated,  the  final  solution  will  contain  sodium 
bicarbonate  and  dissolved  carbon  dioxide.  The  reaction  of  such  a  solution  will  de- 
pend on  the  relative  amounts  of  the  alkaline  bicarbonate  and  the  acid  carbon  dioxide 
present.  This,  in  turn,  will  depend  on  the  tension  of  carbon  dioxide  in  the  air 
with  which  the  mixture  has  been  saturated  and  will  be  independent  of  the  volume 
of  air  blown  through,  provided  saturation  has  once  been  attained.  High  tensions 
of  carbon  dioxide  change  the  reaction  of  the  solution  toward  the  acid  side.  Low 
tensions  have  the  reverse  effect;  hence  the  reaction  of  such  a  solution  is  a  measure 
of  the  tension  of  carbon  dioxide  in  the  air  with  which  it  has  been  saturated.  A 
suitable  indicator  is  added  to  the  solution  and  its  reaction  (after  the  passage  of  the 
alveolar  air)  is  determined  by  comparison  with, a  set  of  suitable  standards. 

Apparatus. — The  complete  apparatus,  including  rubber  bag  for  collection  of 
sample,  standardized  phosphate  mixture  sealed  in  tubes,  the  standard  bicarbonate 
solution,  tubes,  color  comparison  box  and  other  accessories  may  be  obtained  from 
Hynson,  Westcott  and  Dunning,  Baltimore,  Maryland. 

Procedure. — Collection  of  the  alveolar  air.  The  method  of  collection  is  essen- 
tially that  of  Plesch,2  as  modified  by  Higgins.3  A  rubber  bag  of  approximately 
1500  c.c.  capacity4  is  connected  by  means  of  a  short  rubber  tube  to  a  glass  mouth- 
piece.5 About  600  c.c.  of  air  are  blown  into  the  bag  with  an  atomizer  bulb,  and 
the  rubber  tube  clamped  off  by  a  pinchcock.  The  subject  should  be  at  rest  and 
breathing  naturally.6  At  the  end  of  a  normal  expiration,  the  subject  takes  the 
tube  in  his  mouth;  the  pinchcock  is  released  and  the  subject's  nose  closed  by  the 

1  Marriott:  Jour.  Am.  Med.  Ass'n,  66,  1594,  1916. 

2  Plesch:  Ztschr.  f.  exper.  Path.  u.  Therap.,  380,  vi,  1909. 

3  Higgins:  Pub.  203,  Carnegie  Institution  of  Washington,  1915,  p.  168.;  Boothby,  W.  M., 
and  Peabody,  F.  W.:  A  comparsion  of  Methods  of  Obtaining  Alveolar  Air,  Arch.  Int. 
Med.,  March,  1914,  p.  497. 

4  A  basket  ball  bladder  or  a  hot  water  bag  answers  very  well.    If  the  latter  is  used, 
the  neck  may  be  closed  by  a  rubber  stopper  carrying  a  short  glass  tube  %  inch  in 
internal  diameter. 

5  An  ordinary  piece  of  glass  tubing  with  rounded  edges,  i^  inch  long  and  %  inch  in 
internal  diameter. 

6  Especially  to  be  guarded  against  is  a  deep,  voluntary  inspiration  just  before  the  collec- 
tion begins,  as  this  causes  too  low  a  determination. 


322  PHYSIOLOGICAL    CHEMISTRY 

observer.  The  subject  breathes  back  and  forth  from  the  bag  4  times  in  20 
seconds,  emptying  the  bag  at  each  inspiration.  The  observer  should  indicate 
when  to  breathe  in  and  out.  Breathing  more  frequently  will  not  greatly  alter  the 
results.  At  the  end  20  seconds,  the  tube  is  clamped  off  and  the  air  analyzed. 
The  analysis  should  be  carried  out  within  3  minutes'  time,  as  carbon  dioxide 
rapidly  escapes  through  rubber. 

The  foregoing  precedure  applies  to  patients  who  are  capable  of  cooperating 
to  some  extent.  In  the  case  of  comatose  pateints,  the  initial  amount  of  air  in  the 
rubber  bag  must  be  greater  (1000  c.c.  at  least),  and  the  period  of  rebreathing 
prolonged  to  30  seconds.1  This  is  necessary,  as  it  is  not  feasible  that  the  bag  be 
completely  emptied  of  air  at  each  inspiration;  and  therefore  a  longer  time  is  required 
for  the  carbon  dioxide  tension  in  the  bag  and  in  the  lungs  to  become  equal.  The 
initial  amount  of  air  in  the  bag  should  be  such  that  it  is  at  least  one-half  and  prefer- 
ably as  much  as  two-thirds  emptied  at  each  inspiration.  Since  comatose  patients 
cannot  hold  the  mouthpiece,  some  form  of  mask  is  necessary.  This  may  be  a  gas 
anesthetic  mask2  or  such  a  device  as  described  below  for  use  with  infants. 

A  special  mask  has  been  devised  for  the  collection  of  alveolar  air  from  infants.3 
It  is  made  from  the  nipple  of  a  wide-mouth  (Hygeia)  nursing  bottle  and  a  piece 
of  thin  rubber  tissue  (dental  dam).  A  sheet  of  the  tissue  (8  by  10  inches)  is  per- 
forated in  the  center  by  a  piece  of  hot  metal  or  glass  tubing  of  large  bore.  The 
hole  is  stretched  and  pulled  over  the  nipple  and  slipped  down  to  the  lower  rim. 
A  small  amount  of  rubber  cement  is  applied  to  hold  the  tisssue  and  nipple  together. 
A  strip  of  adhesive  plaster  %  inch  wide  is  applied  around  the  rim  of  the  nipple 
so  as  to  overlap  the  rubber  tissue  and  hold  it  firmly  in  place.  The  extreme  tip  of 
the  nipple  is  cut  off  and  a  short  glass  tube,  %  inch  in  diameter,  inserted. 

"In  making  a  collection  of  alveolar  air  from  infants  a  rubber  bag  of  500  c.c 
capacity  is  connected  with  the  mask  and  partially  filled  with  air  by  means  of  an 
aspirator  bulb.  The  neck  of  the  bag  is  closed  off  by  a  pinchcock  or  with  the  fingers, 
the  mask  placed  over  the  nose  and  mouth  of  the  infant  and  the  rubber  tissue  closely 
drawn  around  the  face  so  as  to  prevent  the  escape  of  air.  The  mask  should,  if 
possible,  be  placed  over  the  face  just  at  the  end  of  expiration.  Respirations  are 
allowed  to  continue  for  from  28  to  32  seconds,  and  at  the  end  of  an  expiration 
the  neck  of  the  bag  is  closed  off  and  the  mask  removed  from  the  face.  We 
have  found  that  it  is  necessary  that  the  infant  should  be  breathing  quietly 
for  i  minute  previous  to  the  collection  of  the  air  sample,  as  vigorous  crying, 
just  before  the  mask  is  put  on,  leads  to  a  lowering  of  the  carbon  dioxide 
tension,  as  determined,  by  several  millimeters.  Crying  during  the  collection  of 
the  sample  almost  invariably  occurs  and  facilitates  mixing  of  the  gases.  The 
effect  is  to  raise  the  tension  somewhat  if  crying  is  very  vigorous,  but  not  to  such  an 
extent  as  to  be  significant.  The  initial  amount  of  air  in  the  bag  must  be  such  that 
during  inspiration  the  bag  is  from  one-half  to  two-thirds  empty,  but  never  com- 
pletely collapsed.  The  amount  of  air  required  for  infants  under  i  year  of  age  varies 
from  250  c.c.  to  400  c.c." 

1  The  bag  is  clamped  at  the  end  of  that  expiration  occurring  nearest  to  30  seconds, 
as  no  great  error  is  introduced  by  prolonging  the  time  of  rebreathing  by  2  or  3  seconds. 

2  Some  advantage  may  be  gained  by  inserting  a  large  three-way  stopcock  of  metal 
or  glass  between  the  mask  and  the  bag.     When  such  a  stopcock  is  used,  the  mask  is  first 
put  in  place  on  the  patient's  face  with  the  cock  so  turned  that  he  breathes  the  outside  air 
for  a  few  respirations.    At  the  end  of  an  expiration  the  cock  is  quickly  turned  so  as  to 
bring  the  bag  and  the  mask  into  connection. 

3Howland  and  Marriott:  Am.  Jour.  Dis.  Child.,  May,  1916. 


RESPIRATION   AND    ACIDOSIS  323 

The  mask  described  above  for  use  with  infants  may  be  very  conveniently 
used  for  the  collection  of  alveolar  air  samples  from  dogs.  The  animal's  nose  is 
inserted  into  the  mask  and  the  rubber  tissue  drawn  closely  around  the  muzzle. 
The  time  of  a  collection  need  not  exceed  25  seconds. 

Analysis  of  Sample. — In  analyzing  a  sample  of  air,  about  2  or  3  c.c.  of  the 
standard  bicarbonate  solution  are  poured  into  a  clean  test-tube  of  the  same  diameter 
as  the  tubes  containing  standard  phosphate  solutions,  but  from  100  to  150  mm. 
long.  Air  from  the  bag  is  then  blown  through  the  solution  by  means  of  a  glass 
tube  drawn  out  to  a  fine  capillary  point,  until  the  solution  is  saturated,  as  shown  by 
the  fact  that  no  further  color  change  occurs.1  The  tube  is  stoppered  and  the 
color  immediately  compared  with  that  in  the  standard  tubes.  By  interpolation, 
one  can  readily  read  to  millimeters.  Color  changes  are  not  quite  so  sharp  above 
35  mm.  as  at  the  lower  end  of  the  scale,  but  here  changes  are  of  less  significance. 
In  making  the  color  comparisons  the  solution  being  compared  is  placed  between  the 
two  standards  which  it  most  nearly  matches.  When  there  is  doubt  as  to  whether 
the  color  of  the  solution  is  higher  or  lower  than  one  of  the  standards,  changing 
the  order  in  which  the  tubes  are  placed  in  the  comparison  box  will  generally  make 
the  relationship  clear. 

The  standard  solutions  described  are  so  prepared  as  to  give  correct  results 
when  the  determination  is  carried  out  at  a  temperature  of  from  20°  to  25°C.  (from 
68°  to  77°F.).  When  the  room  temperature  is  considerably  higher  or  lower  than 
these  points  it  is  advisable  to  immerse  the  tubes  in  water  at  approximately  25°C. 
during  the  blowing.  They  may  be  removed  from  the  water  for  the  color  compari- 
son, however,  provided  this  is  quickly  made.  The  differences  due  to  ranges  of 
temperature  occurring  under  ordinary  circumstances  are  practically  negligible.2 

Calculation. — The  standard  tubes  are  marked  to  indicate  the  carbon  dioxide 
tension  in  millimeters  of  mercury,  and  the  readings  can  be  estimated  to  about  2  mm. 

Interpretation. — In  normal  adults  at  rest  the  carbon  dioxide  tension  in  the 
alveolar  air,  determined  and  described  above,  varies  from  40  to  45  mm.  Tensions 
between  30  and  35  mm.  are  indicative  of  a  mild  degree  of  acidosis.  When  the  ten- 
sion is  as  low  as  20  mm.,  the  individual  may  be  considered  in  imminent  danger. 
In  coma,  associated  with  acidosis,  the  tension  may  be  as  low  as  8  or  10  mm. 
In  infants,  the  tension  of  carbon  dioxide  is  from  3  to  5  mm.  lower  than  in  adults. 

Conditions  other  than  acidosis  may  affect  the  carbon  dioxide  tension.  Stimu- 
lation of  the  respiratory  center  leads  to  increased  pulmonary  ventilation  and  a 
consequent  lowering  of  the  alveolar  carbon  dioxide  tension.  Such  stimulation 
may  be  brought  about  by  caffein3  and  possibly  also  by  intracranial  lesions.  The 
respiratory  center  may  be  depressed  by  morphin,  and  as  the  result  of  certain8 
infections.  This  leads  to  an  increased  carbon  dioxide  tension.  Changes  in  the 
excitability  of  the  respiratory  center,  however,  are  but  rarely  great  enough  to  affect 
significantly  the  composition  of  the  alveolar  air. 

"Alveolar"  air  collected  as  described  above  is  essentially  air  which  has  come 

1  If  the  operator  first  blows  his  own  breath  through  the  solution  so  as  to  bring  it  into 
approximate  equilibrium  with  alveolar  air,  saturation  may  be  accomplished  with  as  little 
as  100  c.c.  of  air  from  the  bag,  blown  through  during  30  seconds.    The  same  bicarbonate 
solutions  may  be  used  for  repeated  determinations. 

2  No  correction  for  barometric  pressure  is  required  as  from  the  nature  of  the  determina- 
tion, barometric  fluctuations  are  self-corrective.     Variations  in  the  temperature  of  the 
subject  are  never  great  enough  to  affect  the  value  as  much  as  i  mm.  and  therefore  may 
be  neglected. 

3Higgins  and  Means:  Jour.  Pharmacol.  and  Exper.  Therap.,  1915,  vii,  i. 


324  PHYSIOLOGICAL    CHEMISTRY 

in  equilibrium  with  the  venous  blood  in  the  pulmonary  capillaries.  The  tension 
of  carbon  dioxide  is  approximately  that  in  the  venous  blood.  "Alveolar"  air 
collected  by  the  Haldane  or  Fridericia  methods  is  air  which  has  come  in  approximate 
equilibrium  with  the  arterial  blood,  and  hence  is  of  a  carbon  dioxide  tension  from 
10  to  20  per  cent  lower. 

Changes  in  the  pulmonary  epithelium  such  as  would  prevent  the  air  in  the  lungs 
from  coming  in  equilibrium  with  the  blood  in  the  capillaries  would,  of  necessity, 
affect  the  composition  of  the  alveolar  air.  Since  very  little  is  known  as  yet  regarding 
the  exact  effect  of  such  changes,  one  is  hardly  justified  in  drawing  conclusions 
regarding  acidosis  from  the  composition  of  the  alveolar  air  in  patients  with 
pulmonary  affections.1 

4.  Alkali  Reserve.  Indirect  Method.  Index  of  Acid  Excretion  in 
Urine.  Method  of  Fitz  and  Van  Slyke.  *  Principle.  —  The  method  de- 
pends upon  the  determination  of  the  rate  of  excretion  of  acid  (NH8  + 
titratable  acid)  from  which  the  plasma  carbon  dioxide  capacity  is 
calculated. 

Procedure.  —  Collect  the  urine  for  24  hours  (or  if  desired  for  a  period  of  I 
or  2  hours  during  which  the  subject  ingests  neither  food  nor  water).  In  the 
latter  case  the  urine  collection  should  not  be  too  soon  after  a  meal.  Measure, 
carefully,  the  volume  of  the  urine  and  determine  its  ammonia  content  according 
to  the  method  given  on  page  519  and  the  titratable  acid  according  to  the  method 
given  on  page  499.  Obtain  the  body  weight  of  the  patient. 

Calculation.  —  The  plasma  bicarbonate  may  be  calculated  by  substitution 
in  the  following  equation. 


Plasma  Carbon  Dioxide  Capacity  =  8o3  —  5  \w 

D  =  Rate  of  excretion  per  24  hours. 
W  =  Body  weight  in  kilograms. 

The  value  D  is  equal  to  the  product  VC,  hi  which  V  is  the  24  hour  volume4 
expressed  hi  liters,  and  C  the  sum  of  the  ammonia  (expressed  as  c.c.  of  N/io 
NH3  per  liter  of  urine)  plus  the  titratable  acid  (expressed  as  c.c.  of  N/io  acid 
per  liter  of  urine).  For  practical  purposes  the  acid  excretion  may,  without 
going  through  the  calculation  of  the  formula,  be  interpreted  directly  into  terms 
of  clinical  severity  of  acidosis,  as  indicated  in  the  table  on  page  317,  e.g.,  an 
excretion  exceeding  27  c.c.  of  N/io  ammonia  plus  titratable  acid  per  kilo  in- 
dicates acidosis,  which  usually  becomes  critical  in  severity  if  the  excretion 
approaches  100  c.c.  per  kilo. 

Interpretation.  —  After  careful  investigation  in  which  the  relation- 
ship between  the  carbon  dioxide  capacity  of  plasma  and  the  excretion 
rate  and  concentration  of  total  urinary  acid  excreted  in  excess  of 

1  Means,  Newburgh  and  Porter:  Boston  Med.  and  Surg.  Jour.,  1915,  clxxiii,  742. 

2  Fitz  and  Van  Slyke:  Jour.  Biol.  Chem.,  30,  389,  1917;  Van  Slyke:  Ibi4.t  33,  271, 
1918;  Barnett:  Jour.  Biol.  Ghent.,  33,  267,  1918. 

3  The  value  80  represents  the  maximum  normal  value  of  plasma  bicarbonate.     Under 
such  a  condition  the  titratable  acid  and  ammonia  excretion  tend  to  approach  zero. 

4  If  the  urine  is  collected  for  only  i  or  2  hours  its  volume  is,  of  course,  multiplied  by  24 
or  12  as  the  case  may  be. 


RESPIRATION    AND    ACIDOSIS  325 

mineral  bases  was  determined,  Fitz  and  Van  Slyke  concluded  that 
no  other  equation  including  excretion  rate  and  concentration  was  so 
satisfactory  as  the  above  simplification  of  that  used  by  Ambard 
for  urea  and  chloride.1 

The  value  80  —  5-v/w  indicates,  with  an  error  which  is  usually 

less  than  10  volumes  per  cent,  the  level  of  the  plasma  carbon  dioxide 
capacity.  Diabetics  receiving  bicarbonate  administrations  are  excep- 
tions, the  blood  bicarbonate  in  such  cases  being,  as  a  rule,  much  higher 
than  indicated  by  the  urine. 

Of  the  two  indirect  measures  of  alkali  reserve  the  alveolar  carbon 
dioxide  determination  appears  the  more  accurate  in  measuring  the 
more  severe  stages  of  diabetic  acidosis,  such  as  are  encountered  in 
threatened  coma,  while  the  index  of  acid  excretion  is  the  more  accurate 
in  measuring  the  more  common  intermediate  stages.2 

In  nephritis,  acidosis  (lowered  blood  bicarbonate)  may  occur  with- 
out increase  in  acid  excretion  or  even  with  decrease  of  the  latter. 
Consequently  the  excretion  cannot  be  used  as  an  indicator  of  acidosis 
when  nephritis  is  present. 

For  values  of  the  acid  index  under  different  conditions  see  table, 
page  317. 

5.  Alkali  Tolerance.3 — This  method  is  quite  reliable  for  proving 
the  absence  of  acidosis,  but  is  not  particularly  dependable  for  show- 
ing either  the  presence  or  the  degree  of  acidosis  when  it  exists.  This 
seems  to  be  due  in  part  at  least  to  the  fact  that  in  conditions  asso- 
ciated with  acidosis  the  power  of  the  kidney  for  excretion  of  alkalies 
may  be  markedly  impaired. 

Principle.—  Sodium  bicarbonate  is  administered  in  small  amounts, 
either  by  mouth  or  intravenously  until  the  reaction  of  the  urine  changes 
from  acid  to  alkaline.  The  amount  of  bicarbonate  is  then  noted. 

Procedure. — Give  (by  mouth)  5  grams  of  sodium  bicarbonate  in  100  c.c. 
of  water  to  the  subject  under  examination.  Repeat  every  half  hour  until  the 
total  bicarbonate  administration  is  equivalent  to  0.5  gram  per  kilogram  of  body 
weight  unless  the  urine  becomes  alkaline  before  that  time.  In  case  the  urine 
does  not  become  alkaline  with  the  above  bicarbonate  ingestion,  continue  the 
administration  of  the  alkali  until  the  urine  shows  an  alkaline  reaction.4  The 
urine  should  be  voided  by  the  subject  before  each  administration  of  bicarbonate. 
Test  each  specimen  of  urine  with  litmus,  boiling  those  samples  which  are  only 

1  Ambard:  Physiologic  normale  et  pathologique  des  reins,  Paris,  1914. 

2  Stillman,  Van  Slyke,  Cullen,  and  Fitz:  Jour.  Biol.  Chem.,  30,  405,  1917. 
'Sellards:  Bull.  Johns  Hopkins  Hosp.,  23,  289,  1912;  Palmer  and  Henderson:  Arch. 

Int.  Med.,  12,  153,  1913;  Palmer  and  Van  Slyke:  Jour.  Biol.  Chem.,  32,  499,  1917. 

4  Because  of  the  likelihood  of  producing  a  condition  of  alkalosis  it  is  advisable  not  to 
continue  the  administration  of  bicarbonate  without  evidence  from  blood  analysis  showing 
an  alkali  deficit. 


326  PHYSIOLOGICAL    CHEMISTRY 

faintly  acid  so  that  any  bicarbonate  present  will  be  converted  to  carbonate. 
Note  the  number  of  grams  of  bicarbonate  necessary  to  produce  an  alkaline  urine. 

Interpretation. — Normally  the  administration  of  from  5  to  10  grams 
of  bicarbonate  is  generally  sufficient  to  produce  an  alkaline  reaction 
in  the  urine,1  while  in  patients  suffering  from  acidosis  a  greater  amount 
is  required.  In  general  a  maximum  ingestion  of  0.5  gram  of  bicarbonate 
per  kilogram  body  weight  will  produce  an  alkaline  urine  in  a  normal 
person.  In  mild  acidosis  this  value  may  be  increased  to  a  maximum 
of  0.8  gram,  whereas,  moderate  acidosis  may  show  a  value  of  i.i 
grams.  In  severe  acidosis  with  symptoms  of  acid  intoxication  the 
bicarbonate  value  may  exceed  i.i  grams  per  kilogram  body  weight. 
If  an  alkaline  urine  is  obtained  after  the  administration  of  0.5  gram 
or  less  of  bicarbonate  per  kilogram  body  weight  one  is  safe  in  saying 
that  no  acidosis  exists.  When  higher  values  are  obtained,  however, 
they  should  be  Confirmed  by  blood  analysis  before  being  accepted. 
For  data  as  to  alkali  tolerance  under  different  conditions  see  table  on 
page  317. 

6.  Relative  Hydrogen  Ion  Concentration  of  the  Blood.  Method  of  Levy, 
Rownlree,  and  Marriott?  Principle. — The  blood  is  dialyzed  against  normal  salt 
solution  and  the  H  ion  concentration  of  the  protein-free  dialyzate  is  determined 
by  the  indicator  method,  using  phenolsulphonephthalein. 

Procedure. — One  to  3  c.c.  of  clear  serum  or  of  blood  is  run,  by  means  of  a 
blunt-pointed  pipette,  into  a  dialyzing  sac3  which  has  been  washed  outside  and 
inside  with  salt  solution.4  The  sac  is  lowered  into  a  small  test-tube  (100X10 
mm.,  inside  measurements),  containing  3  c.c.  of  salt  solution,  until  the  fluid  on  the 
outside  of  the  sac  is  as  high  as  on  the  inside.  From  5-10  minutes  are  allowed  for 

1  Henderson  &  Palmer:  Jour.  Biol.  Chem.   14,81,  1913. 

2 Levy,  Rowntree  and  Marriott:  Arch.  Int.  Med.,  16,  389,  1915. 

3  Preparation  of  Sacs. — One  ounce  of  celloidin  is  dissolved  in  500  c.c.  of  a  mixture  of 
equal  quantities  of  ether  and  ethyl  alcohol.     The  solid  swells  up  and  dissolves  with  oc- 
casional gentle  shakings,  in  48  hours.     As  a  small  amount  of  brown  sediment  separates 
out  at  first,  the  solution  should  stand  for  at  least  three  or  four  days,  after  which  the  clear 
supernatant  solution  is  ready  for  use.     A  small  test-tube  (120  by  9  mm.,  inside  measure- 
ment) is  filled  with  this  mixture,  inverted,  and  half  the  contents  poured  out.     The  tube  is 
then  righted,  and  the  collodion  allowed  to  fill  the  lower  half  again.     A  second  time  it  is 
inverted  and  rotated  on  its  axis,  the  collodion  being  drained  off.     Care  must  be  taken  to 
rotate  the  tube,  in  order  to  secure  a  uniform  thickness  throughout.     The  tube  is  clamped 
in  the  inverted  position  and  allowed  to  stand  for  ten  minutes,  until  the  odor  of  ether  finally 
disappears.     It  is  filled  five  or  six  times  with  cold  water,  or  it  is  allowed  to  soak  five  minutes 
in  cold  water.     A  knife  blade  is  run  around  the  upper  rim,  so  as  to  loosen  the  sac  from  the 
rim  of  the  test-tube,  and  a  few  cubic  centimeters  of  water  are  run  down  between  the  sac 
and  the  glass  tube.     By  gentle  pulling  the  tube  is  extracted,  after  which  it  is  preserved  by 
complete  immersion  in  water. 

4  The  Salt  Solution. — The  blood  or  serum  is  dialyzed  against  an  0.8  per  cent  sodium 
chloride  solution. 

Before  applying  the  test,  it  is  necessary  to  ascertain  that  the  solution  is  free  from  acids 
other  than  carbonic.  To  determine  this,  a  few  cubic  centimeters  of  the  salt  solution  are 
placed  in  a  Jena  test-tube  and  i  or  2  drops  of  the  indicator  added,  whereupon  a  yellow  color 
appears.  On  boiling,  carbon  dioxide  is  expelled,  and  the  solution  loses  its  lemon  color 
and  takes  on  a  slightly  brownish  tint.  In  the  absence  of  this  change  other  acids  are 
present,  and  the  salt  solution  is  therefore  not  suitable.  If,  on  the  other  hand,  on  adding 
the  indicator  pink  at  once  appears,  the  solution  is  alkaline  and  hence  cannot  be  used. 


RESPIRATION   AND    ACIDOSIS 


327 


dialysis.  The  collodion  sac  is  removed  and  5  drops  of  the  indicator  (o.oi  per 
cent  solution  of  phenolsulphonephthalein)  are  thoroughly  mixed  with  the  dialyzate. 
The  tube  is  then  compared  with  the  standards1  until  the  corresponding  color  is 
found,  which  indicates  the  hydrogen  ion  concentration  present  in  the  dialyzate. 
Readings  should  be  made  immediately  against  a  white  background.  Results 
are  expressed  in  logarithmic  notation. 

Oxalated  blood  from  normal  individuals  gives  a  dialyzate  with  a  PH  varying 
from  7.4  to  7.6,  while  that  of  serum  ranges  from  7.6  to  7.8.  In  clinical  acidosis  fig- 
ures from  7.55  to  7.2  have  been  noted  by  this  method  for  serum  and  for  oxalated 
blood  from  7.3  to  7.  i .  A  rise  in  the  H  ion  concentration  of  the  blood  is  significant 
because  it  indicates  a  failure  on  the  part  of  the  protective  mechanism  of  the  body 
to  preserve  the  proper  reaction. 


TABLE  FOR  PREPARATION  OF  STANDARD  COLORS 


PH  

6.4 

6.6 

6.8 

7-0 

7-1 

7-2 

7-3 

7-4 

7-5 

7-6 

7-7 

7-8 

8.0 

8.2 

8.4 

Primary       potassium 

phosphate  c.c  

77 

63 

51 

17 

3? 

77 

73 

T9 

15  8 

13.2 

ii  .0 

R  8 

5  6 

3.2 

2.O 

Secondary        sodium 

-„ 

phosphate  c.c  

27 

37 

49 

63 

68 

73 

77 

81 

84.2 

86.8 

89.0 

91.2 

94.4 

96.8 

98.0 

7.  Acetone  Bodies. — For  methods  of  determining  acetone,   acetoacetic  and 
|8-hydroxybutyric  acids  in  the  blood  see:  Van  Slyke  and  Fitz,  Jour.  Biol.  Chem.  32, 
495,  1917;  Marriott:  Jour.  Biol.  Chem.  16,  289,  293,  and  295,  1913. 

8.  Determination  of  Oxygen  and  Oxygen  Capacity  (or  Hemoglobin) 
of  the  Blood. — It  is  possible  to  determine  the  oxygen  content  of  blood,2 
using  the  same  apparatus  as  that  employed  for  the  C02  estimation 
(see  p.  311),  suitable  precautions  being  taken  in  collecting  the  blood 
for  analysis. 

The  oxygen  capacity  of  blood  is  a  measure  of  its  hemoglobin  content. 
It  may  be  determined  gasometrically,  using  the  method  of  Van  Slyke 
mentioned  above.  It  is  more  conveniently  estimated  by  one  of  the 
colorimetric  methods  for  hemoglobin.  Several  clinical  methods  re- 
quiring the  use  of  special  forms  of  apparatus  are  widely  employed. 
Among  these  may  be  mentioned  the  Dare,  Fleischl-Miescher,  and 
Sahli  methods,  based  on  the  use  of  undiluted  blood,  diluted  blood,  and 

1  Preparation  of  Standard  Colors. — Standard  phosphate  mixtures  are  prepared  according 
to  Sorensen's  directions  as  follows: 

J^5  mol.  acid  or  primary  potassium  phosphate.  9.078  grams  of  the  pure  recrystallized 
salt  (KH2PO4)  is  dissolved  in  freshly  distilled  water  and  made  up  to  i  liter. 

3^5  mol.  alkaline  or  secondary  sodium  phosphate.  The  pure  recrystallized  salt 
(Na2HPO4.i2H2O)  is  exposed  to  the  air  for  from  ten  days  to  two  weeks,  protected  from 
dust.  Ten  molecules  of  water  of  crystallization  are  given  off  and  a  salt  of  the  formula 
Na2HPO4.2H2O  is  obtained.  11.876  grams  of  this  is  dissolved  in  freshly  distilled  water 
and  made  up  to  i  liter.  The  solution  should  give  a  deep  rose-red  color  with  phenol- 
phthalein.  If  only  a  faint  pink  color  is  obtained,  the  salt  is  not  sufficiently  pure. 

The  solutions  are  mixed  in  the  proportions  indicated  below  to  obtain  the  desired  PH. 

2  Van  Slyke  D.  D.:  Jour.  Biol.  Chem.,  33,   127,   1918;  Lundsgaard,   C.:  Jour.  Biol. 
Chem.,  33,  133,  1918. 


328  PHYSIOLOGICAL   CHEMISTRY 

the  formation  of  acid  hematin  respectively.  Hemoglobin  may  be 
more  accurately  determined  using  one  of  the  ordinary  forms  of  colori- 
meter and  either  the  carbon  monoxide  hemoglobin  method  of  Palmer1 
or  the  acid  hematin  method  as  applied  by  Cohen  and  Smith2  and 
Robscheit.3  In  each  of  these  methods,  the  standard  is  controlled  by 
the  Van  Slyke  gasometric  method  (see  above). 

9.  Determination  of  Respiratory  Exchange. — The  output  of  carbon 
dioxide  and  consumption  of  oxygen  by  the  human  body  during  a  given 
period  of  time  may  be  measured  by  means  of  one  of  a  number  of  rela- 
tively simple  forms  of  respiration  apparatus  which  have  been  developed 
of  recent  years.4  These  have  found  their  chief  clinical  application 
in  the  study  of  patients  with  suspected  thyroid  disease,  hyperthyroidism 
bringing  about  an  increase  and  hypothyroidism  a  decrease  in  the  basal 
metabolic  rate  or  the  minimal  heat  production  of  the  body  at  complete 
muscular  rest  12  to  18  hours  after  the  ingestion  of  food.  The  direct 
measurement  of  this  heat  production  involves  the  use  of  a  complicated 
respiration  calorimeter,  but  it  is  easily  measured  indirectly  from  the 
oxygen  consumption  and  with  a  fair  degree  of  accuracy.  An  idea  as 
to  the  increased  consumption  of  oxygen  during  muscular  work  may  also 
be  obtained  by  collecting  the  air  expired  by  the  working  individual 
in  a  large  air-tight  bag  carried  over  the  shoulders,  measuring  and  analyz- 
ing it  for  oxygen  and  carbon  dioxide.5 

10.  Simple  Demonstration  of  the  Presence  of  Carbon  Dioxide  in  Expired 
Air. — (a)  Into  each  of  two  small  flasks  or  large  test  tubes  introduce  25  c.c.  of  a 
clear  saturated  solution  of  barium  hydroxide.  After  an  ordinary  inspiration, 
expire  through  a  bent  glass  tube  or  pipette  dipped  beneath  the  surface  of  the 
solution  in  the  first  flask.  Repeat  the  experiment  with  flask  number  two  but 
hold  the  breath  as  long  as  possible  after  the  inspiration  before  breathing  out 
through  the  tube.  Note  the  relative  amounts  of  precipitate  of  barium  carbonate' 
formed. 

(b)  Into  each  of  two  large  test  tubes  introduce  about  20  c.c.  of  water  and 
1-2  drops  of  saturated  barium  hydroxide  solution.  To  the  first  add  a  few  drops 
of  phenolphthalein  solution  and  to  the  second  a  few  drops  of  phenolsulphone- 
phthalein  solution.  Expire  through  each  of  these  until  a  change  takes  place. 
What  does  this  change  indicate? 

Calmer,  W.  W.:  Jour.  Biol.  Chem.,  33,  119,  1918. 

2  Cohen,  B.,  and  Smith,NA.  H.:  Jour.  Biol.  Chem.,  39,  489,  1919. 

3  Robscheit,  P\  S.:  Jour.  Biol.  Chem.,  41,  209,  1920. 

4  Benedict,  F.  G.:  Boston  Med.  and  Surg.  Jour.,  178,  567,  1918.     Boothby,  W.  M.,  and 
Sandiford,  I.:  "Basal  Metabolic  Rate  Determinations,"  W.  B.  Saunders,  Philadelphia, 
1920.     Jones,  H.  M.:  Jour.  Am.  Med.  Ass'n.,  75,  538,  1920. 

6  R.  G.  Peafce  in  Macleod,  J.  J.  R. :  "Physiology  and  Biochemistry  in  Modern  Medicine," 
p.  554,  C.  V.  Mosby  Co.,  St.  Louis,  1918. 


CHAPTER  XVIII 
MILK 

MILK  is  the  most  satisfactory  individual  food  material  elaborated 
by  nature.  It  contains  the  three  nutrients,  protein,  fat,  and  carbohy- 
drate and  inorganic  salts  in  such  proportion  as  to  render  it  a  very 
acceptable  dietary  constituent.  Its  dietary  value  is  also  enhanced  by 
the  presence  of  the  three  mtamines,  Fat-soluble  A,  Water-soluble  B 
and  Water-soluble  C.  Milk  would  be  an  ideal  food  were  it  not  for  its 
low  iron  content  and  for  a  slight  deficiency  in  water-soluble  B.1  Milk 
is  a  specific  product  of  the  secretory  activity  of  the  mammary  gland. 
It  contains,  as  the  principal  solids,  olein,  palmitin,  stearin,  butyrin, 
casein,  lactalbumin,  lacto- globulin,  lactose,  phosphates  of  c-alcium,  potas- 
sium and  magnesium,  citrates  of  sodium  and  potassium,  chloride  of 
calcium,  iron  and  mtamines.  It  also  contains  at  least  traces  of  lecithin, 
cholesterol,  urea,  creatine,  creatinine,  and  the^tri-glycerides  of  caproic, 
lauric  and  myristic  acids.  The  calcium  phosphate  of  milk  is  the 
neutral  calcium  phosphate,  CaHP04.2  According  to  Osborne  and 
Wakeman3  milk  contains  two  phosphatides,  one  being  probably  stearyl- 
oleyl-lecithin.  These  same  investigators4  have  also  shown  milk  to 
contain  an  alcohol-soluble  protein. 

The  presence  of  the  vitamine  Fat-soluble  A  in  butter  fat  was  first 
demonstrated  by  McCollum  and  DaVis  and  by  Osborne  &  Mendel.5 
For  discussion  of  vitamines,  see  Experiment  I,  page  580.) 

Summer  milk  has  a  higher  vitamine  content  than  winter  milk.6 

The  preparation  of  milk  in  the  form  of  a  powder  has  become  an 
important  industry. 

By  passing  milk  through  a  special  form  of  earthenware  filter  Van 
Slyke  and  Bosworth7  have  obtained  a  separation  of  the  constituents 
in  milk  which  are  in  true  solution  from  those  insoluble  in  water  or  in 
suspension.  The  soluble  constituents  and  the  water  constitute  the 

Osborne  and  Mendel:  Jour.  Biol.  Chem.,  41,  515,  1920. 

2  Van  Slyke  and  Bosworth:  Jour.  Biol.  Chem.,  20,  135,  1915. 

3 Osborne  and  Wakeman:  Jour.  Biol.  Chem.,  21,  539,  1915;  28,  i,  1916.      /^ 

4  Osborne  and  Wakeman:  Jour.  Biol.  Chem.,  33,  243,  1918. 

5  McCollum  and  Davis:  Jour.  Biol.  Chem.,  15,  167,  1913;  Osborne  and  Mendel:  ibid., 
15,  311,  1913;  24,  37,  1916  (previous  references  cited  in  this  article). 

6  Hart,  Steenbock  and  Ellis:  Jour.  Biol.  Chem.,  42,  383, 1920.     Hess,  Unger  and  Supplee: 
Jour.  Biol.  Chem.,  45,  229,  1920.     Dutcher,  Kennedy  and  Eckles:  Science,  52,  December 
17,  1920. 

7  Van  Slyke  and  Bosworth:  Jour.  Biol.  Chem.,  20,  135,  1915. 

329 


330  PHYSIOLOGICAL  CHEMISTRY 

milk  serum.  Their  classification  of  milk  constituents  in  a  slightly 
modified  form  follows: 

CONSTITUENTS  OF  MILK 

In   true   solution   in  milk      Partly    in    solution    and        Entirely  in  suspension  or 

milk  serum.  partly  in  suspension  or  col-  colloidal  solution. 

loidal  solution. 

1.  Lactose.  i.  Albumin.                              i.  Fat. 

2.  Citric  acid.  2.  Inorganic  phosphate.           2.  Casein. 

3.  Potassium.  3.  Calcium.                              3.  Fat-soluble  A. 

4.  Sodium.  4.  Magnesium. 

5.  Chlorine. 

6.  Water-soluble  B. 

7.  Water-soluble  C. 

Fresh  milk,  both  human  and  cow's,  is  amphoteric  in  reaction  to 
litmus  and  acid  to  phenolphthalein.  The  acidity  is  believed  to  be  due 
in  part  at  least  to  soluble  acid  phosphates.  Upon  standing  for  a 
sufficiently  long  time,  unsterilized  milk  sours,  i.e.,  it  becomes  strongly 
acid  in  reaction  to  litmus  due  to  the  production  of  the  optically  in- 
active fermentation  lactic  acid, 

H     OH 

I       I 
H—  C—  C—  COOH, 

I       I 
H    H 

from  the  lactose  contained  in  it.  This  is  brought  about  through 
bacterial  activity.  The  white  color  is  imparted  to  the  milk  partly 
through  the  fine  emulsion  of  the  fat  and  partly  through  the  medium  of 
the  caseinogen  in  solution.  The  specific  gravity  of  milk  varies  some- 
what, the  average  being  about  1.030.  Its  freezing-point  is  about 
-o.56°C. 

This  lactic  acid  fermentation  may  be  brought  about  by  Bact.  lactis 
acidi  and  other  microorganisms.  Certain  putrefactive  bacteria  in  the 
human  intestines  may  also  cause  lactic  acid  fermentation.  The  chem- 
ical changes  in  lactic  acid  fermentation  may  be  indicated  thus: 

Ci2H22On  +  H20-»  C6H1206  +  C6Hi206 

Lactose.  Galactose.  Glucose. 


Galactose  Lactic  Acid. 

or  Glucose. 

Fresh  milk  does  not  coagulate  on  being  boiled  but  a  film  consisting 
of  a  combination  of  casein  and  calcium  salts  forms  on  the  surface. 
If  the  film  be  removed,  thus  allowing  a  fresh  surface  to  come  into 
contact  with  the  air,  a  new  film  will  form  indefinitely  upon  the  applica- 
tion of  heat.  Surface  evaporation  and  the  presence  of  fat  facilitate 


MILK  331 

the  formation  of  the  film,  but  are  not  essential  (Rettger1).  As  Jamison 
and  Hertz2  have  shown,  a  similar  film  will  form  on  heating  any  protein 
solution  containing  fat  or  paraffin.  If  the  milk  is  of  a  pronounced 
acid  reaction,  through  the  inception  of  lactic  acid  fermentation,  or  from 
any  other  cause,  no  film  will  form  when  heat  is  applied,  but  instead  a 
true  coagulation  will  occur.  When  milk  is  boiled  certain  changes  occur 
in  its  odor  and  taste.  These  changes,  according  to  Rettger,3  are  due 
to  a  partial  decomposition  of  the  milk  proteins  and  are  accompanied 
by  the  liberation  of  a  volatile  sulphide,  probably  hydrogen  sulphide. 


FIG.  104. — NORMAL  MILK  AND  COLOSTRUM. 
a,  Normal  milk;  b,  Colostrum. 

The  milk-curdling  enyzmes  of  the  gastric  and  the  pancreatic  juice 
have  the  power  of  splitting  the  casein  of  the  milk,  through  a  process  of 
hydrolytic  cleavage,  into  soluble  paracasein  and  a  peptone-like  body. 
This  soluble  paracasein  then  forms  a  combination  with  the  soluble 
calcium  salts  of  the  milk  and  an  insoluble  curd  of  paracasein  results. 
The  clear  fluid  surrounding  the  curd  is  known  as  whey.  This  action 
of  rennin  may  be  represented  by  the  following  scheme: 

Casein  (+  rennin) 

I 

Peptone-like  Soluble  paracasein 

body  | 

+  Ca  salts 

I 
Paracasein 

(insoluble  curd) 

1  Rettger:  American  Journal  of  Physiology,  7,  325,  1902. 

2  Jamison  and  Hertz:  Journal  of  Physiology,  27,  26,  1902. 

3  Rettger:  American  Journal  of  Physiology,  6,  450,  1902. 


33  2  PHYSIOLOGICAL  CHEMISTRY 

There  is  still  considerable  confusion  of  terms  when  different  authori- 
ties discuss  milk  proteins  and  the  action  of  milk  curdling  enzymes  upon 


FIG.  105.  .  FTG.  106. 

FIG.  105. — CURD  OF  HUMAN  MILK  5  MINUTES  AFTER  INGESTION  OF  75  c.c.  MILK. 
(Beginning  of  curd  formation,  ^  actual  size).1 

FIG.  105. — CURD  OF  HUMAN  MILK  10  MINUTES  AFTER  INGESTION  OF  75  c.c.  MILK. 
(Maximum  curd  formation,  ^  actual  size).1 

them.     The  English  scientists2  quite  uniformly  call  the  principal  pro- 
tein of  milk  caseinogen  whereas  the  insoluble  curd  formed  by  rennin  is 


FIG.  107.  FIG.  1 08. 

FIG.  107. — CURD  OF  Cow's  MILK  REGURGITATED  10  MINUTES  AFTER  INGESTION  OF 
500  c.c.  WHOLE  MILK.     (Curds  %  actual  size).3 

FIG.  108. — CURD    OF  Cow's  MILK  REGURGITATED  25  MINUTES  AFTER  INGESTION  OF 
500  c.c.  WHOLE  MILK.     (Curds  %  actual  size).3 

FIGS.  105  TO  108.— PHOTOGRAPHS  REPRESENTING  TYPICAL  CURDS  FROM  HUMAN  AND 

Cow's   MILK. 

termed  casein.     On  the  other  hand,  the  Germans  and  many  Americans 
give  the  name  casein  to  the  milk  protein  and  paracasein  to  the  product 

1  Unpublished  photographs  from  the  thesis  of  Dr.  Robert  A.  Lichtenthaeler. 

2  Halliburton:  Journal  of  Physiology,  n,  448,  1900. 

3  Bergeim,  Evvard,  Rehfuss  and  Hawk :  Am.  Jour.  Physiol.,  48,  411,  1919. 


MILK 


333 


of  the  action  of  rennin  upon  this  protein.     The  confusion  of  terms 
may  be  represented   thus: 

English.  German. 

Caseinogen.  =  Casein. 

Casein.  =  Paracasein. 

The  most  important  difference  between  human  milk  and  cow's 
milk  is  in  the  protein  content,  although  there  are  also  differences  in  the 
carbohydrate  and  ash  and  likewise  striking  biological  differences  diffi- 
cult to  define  chemically.  It  has  been  shown  that  the  casein  of  human 
milk  differs  from  the  casein  of  cow's  milk  in  being  more  difficult  to 
precipitate  by  acid  or  coagulate  by  gastric  rennin.  The  casein  curd 
(paracasein)  also  forms  in  much  looser  and  more  flocculent  manner 
than  that  from  cow's  milk  and  is  for  this  reason  much  more  easily 
digested  than  the  latter.  (For  illustrations  of  milk  curds,  see  Figs.  105 
to  1 08,  page  332.)  Both  human  and  cow's  milk  contain  important 
non-nitrogenous  substances  of  an  unknown  character.  Human  milk 
contains  the  greater  quantity  of  these  substances.1 

Non-protein  nitrogen,  urea  and  creatinine  are  present  in  normal 
human  milk  in  approximately  the  same  concentration  as  in  normal 
human  blood2  (See  Blood  Analysis,  p.  273). 

The  relative  composition  of  human  and  cow's  milk  is  shown  in  the 
following  table  which  embraces  data  reported  by  Meigs  and  Marsh. 


COMPOSITION  OF  MILK  (PER  CENT  OF  WHOLE  MILK)  NORMAL  VARIA- 
TIONS FROM  BEGINNING  OF  SECOND  MONTH  OF  LACTATION 


Constituent 

Cow 

Human 

Water  (Avg.)  

87  o 

87.5 

Solids  (Avg.)  

I^  .O 

12.  S 

5 

Protein 

A-2    C3 

I    ^—  O   7  ' 

Fat  

2—  A 

2—4 

Sugar.  . 

7.5-C3 

6-7.5 

Ash.  . 

O   6~O    7 

O    2—  O  .  \ 

The  above  data  indicate  that  human  milk  contains  less  protein, 
more  sugar   and   much   less   ash   than  cow's   milk.     The  percentage 

1  Meigs  and  Marsh:  Jour.  Biol.  Chem.,  16,  147,  1913. 

8  Denis,  Talbot  and  Minot;  Jour.  Biol.  Chem.,  39,  47,  1919. 

*  Protein  starts  high  and  decreases  whereas  sugar  starts  low  and  increases. 


334 


PHYSIOLOGICAL   CHEMISTRY 


composition  of  human  milk  at  different  periods  is  represented  in  the 
following  table.1 

PERCENTAGE  COMPOSITION  OF  HUMAN  MILK  BY  PERIODS 


Period 

Fat 

Sugar 

Protein 

Casein 

Albumin 

Ash 

Total 
solids 

Colostrum  (1—12  days)  

2.83 

7.  SO 

2.2"? 

o.  31 

17     A 

Transition  (i2~3o  days) 

407 

7    74 

i  s6 

O    2A 

T7     A 

' 

3   ?f> 

7.  SO 

i.ic 

0.43 

0.72 

O.2I 

12.2 

Late  (10—20  mos.)  

3   16 

7.47 

1.07 

o.  32 

0.75 

O.2O 

12.2 

The  composition  of  the  ash  of  milk  is  shown  in  the  following  table 
reported  by  Holt,  Courtney  and  Fales.2 

PERCENTAGE  COMPOSITION  OF  THE  ASH  OF  MILK 


CaO 

MgO 

P206 

Na2O 

K20 

a 

Human  milk.  . 

27    -z 

-2      1 

16.6 

7.2 

28.3 

T6  5 

Cow's  milk. 

2?    er 

2.8 

26.5 

7.  2 

24.0 

13  6 

•. 

It  will  be  observed  that  the  composition  of  the  ash  of  the  two  varieties 
of  milk  is  about  the  same  except  for  phosphorus.  The  higher  phos- 
phorus content  in  the  case  of  cow's  milk  is  due  principally  to  the  fact 
that  the  milk  contains  a  higher  percentage  of  casein  or  phospho protein. 
It  should  be  borne  in  mind  that  cow's  milk  contains  on  the  average 
over  three  times  as  much  ash  as  human  milk.  Therefore  unless  cow's 
milk  has  been  diluted  with  more  than  twice  its  volume,  there  is  still 
present  as  high  a  concentration  of  the  inorganic  constituents  as  are 
,  present  in  normal  human  milk.  Hence  there  is  no  necessity  for  the 
addition  of  any  of  these  constituents  in  infant  feeding. 

Interesting  data  relative  to  the  composition  of  milk  from  various 
sources  may  be  gathered  from  the  following  table  which  was  compiled 
mainly  from  the  results  of  investigations  by  Proscher3  and  by  Abder- 
halden4  in  Bunge's  laboratory.  It  will  be  noted  that  the  composition 
of  the  milk  varies  directly  with  the  length  of  time  needed  for  the  young 
of  the  particular  species  to  double  in  weight. 

1Holt,  Courtney  and  Fales:  Am.  Jour.  Dis.  Children,  10,  229,  1915. 

2  Holt,  Courtney  and  Fales:  Am.  Jour.  Dis.  Children,  10,  229,  1915. 

3  Proscher:  Zeit.f.  physiol.  Chemie,  24,  285,  1898. 

4  Abderhalden:  Ibid.,  26,  487,  1899;  and  27,  pp.  408  and  457,  1899. 


MILK 


335 


Species 

Period  in  which 
weight  of  the 
newborn  is 
doubled  (days) 

100  Parts  of  milk  contain 

Proteins 

Salts 

Calcium 

Phosphoric 
acid 

Man                 

180 
60 

47 

22 
IS 
14 

9-5 
9 
6 

1.6 

2.0 

3-5 
3-7 
4-9 
5-2 
7.0 
7-4 
10.4 

0.2 

0.4 
0.7 
0.8 
0.8 
0.8 

I.O 

i-3 
2-5 

0.033 
0.124 
0.160 
0.197 
0.245 
0.249 

0.047 
0.131 
0.197 
0.284 
0.293 
0.308 

Horse                     .... 

Cow       

Goat        

Sheep                  

Pig  . 

Pat 

Dog            

0.455 
0.891 

0.508 
0.997 

Rabbit                  

The  secretion  of  the  mammary  glands  of  the  newborn  of  both  sexes 
is  called  "witches'  milk."  The  name  is  centuries  old  and  evidently 
refers  to  the  mystery  of  the  useless  secretion.  Bj-isch1  has  recently  sug- 
gested that  this  secretion  of  "witches'  milk"  is  brought  about  by  the 
passage  of  hormones  (see  Chapter  on  Pancreatic  Digestion)  from  the 
blood  of  the  mother  to  the  fetus. 


!j  v  FIG.  109. — LACTOSE. 

Lactose,  the  principal  carbohydrate  constituent  of  milk,  is  an  impor- 
tant member  of  the  disaccharide  group.  It  occurs  only  in  milk,  except 
as  it  is  found  in  the  urine  of  women  during  pregnancy,  during  the  nurs- 
ing period,  and  soon  after  weaning;  it  also  occurs  in  the  urine  of  normal 
persons  after  the  ingestion  of  a  very  large  amount  of  lactose  in  the  food. 
It  is  not  derived  directly  from  the  blood,  but  is  a  specific  product  of  the 

1  Basch:  Munch,  med.  Woch.,  58,  2266,  1911. 


336  PHYSIOLOGICAL  CHEMISTRY 

cellular  activity  of  the  mammary  gland.  It  has  strong  reducing  power, 
is  dextro-rotatory  and  forms  an  osazone  with  phenylhydrazine.  Lac- 
tose is  not  fermentable  by  the  ordinary  baker's  yeast.  For  changes 
which  lactose  undergoes  in  lactic  acid  fermentation  see  page  330.  The 
crystalline  form  of  lactose  is  shown  in  Fig.  109. 

Casein,  the  principal  protein  constituent  of  milk,  belongs  to  the 
group  of  phosphoproteins  and  contains  0.7  per  cent  of  phosphorus.1 
It  has  acidic  properties  and  combines  with  bases  to  produce  salts.2 
It  is  probably  present  in  milk  in  the  form  of  neutral  calcium  caseinate 
(Casein  Ca4).3  It  is  not  coagulable  upon  boiling  and  is  precipitated 
from  its  neutral  solution  by  certain  metallic  salts  as  well  as  upon  satu- 
ration with  sodium  chloride  or  magnesium  sulphate.  Its  acid  solu- 
tion is  precipitated  by  mineral  acid. 

Lactalbumin  and  lacto-globulin,  the  protein  constituents  of  milk, 
next  in  importance  to  casein,  closely  resemble  serum  albumin  and 
serum  globulin  in  their  general  properties. 

Butter  (milk  fat)  consists  in  large  part  of  olein  and  palmitin. 
Stearin,  butyrin,  caproin  and  traces  of  other  fats  are  also  present. 
An  important  growth-promoting  substance  (vitamine)  called  "Fat 
Soluble  A"  is  also  present  in  butter  fat.4  When  butter  becomes 
rancid  through  the  cleavage  of  certain  of  its  constituent  fats  by  bacteria 
the  odors  of  caproic  and  butyric  acids  are  in  evidence. 

The  pigment  of  the  fat  of  cow's  milk  is  made  up  of  carotin  and 
xanthophylls .  The  principal  pigment  is  carotin,  an  unsaturated 
hydrocarbon  pigment  which  is  widely  distributed  in  plants.5  The 
pigment  of  the  fat  of  human  milk  is  made  up  of  carotin  and  xantho- 
phylls in  about  equal  proportions.  Carotin  is  also  probably  the 
pigment  of  human  fat.  The  pigment  of  body  fat,  blood  serum,  corpus 
luteum  and  skin  secretions  of  the  cow  is  principally  carotin. 

Colostrum  is  the  name  given  to  the  product  of  the  mammary  gland 
secreted  for  a  short  time  before  parturition  and  during  the  early  period 
of  lactation  (see  Fig.  104,  page  331).  It  is  yellowish  in  color,  contains 
more  solid  matter  than  ordinary  milk,  and  has  a  higher  specific  gravity 
(1.040-1.080).  The  most  striking  difference  between  colostrum  and 
ordinary  milk  is  the  high  percentage  of  lactalbumin  and  lacto-globulin 
in  the  former.  This  abnormality  in  the  protein  content  is  responsible 
for  the  coagulation  of  colostrum  upon  boiling. 

Such   enzymes   as   lipase,   amylase,  galactase,  catalase,  oxidases, 

1  Bosworth  and  Van  Slyke:  Jour.  Biol.  Chem.,  19,  67,  1914. 

2  Van  Slyke  and  Bosworth:  Jour  Biol.  Chem.,  14,  207-227,  1914. 
»  Van  Slyke  and  Bosworth:  Jour.  Biol  Chem.,  20,  135,  1915, 

4  See  Experiment  i,  page  580. 

6  Palmer  and  Eckles:  Jour.  Biol.  Chem.,  17,  191,  1914. 


MILK  337 

peroxidases,  and  reductases  have  been  identified  in  milk,  but  not  all  of 
them  in  milk  of  the  same  species  of  animal. 

Among  the  principal  preservatives  used  in  connection  with  milk  are 
formaldehyde,  hydrogen  peroxide,  boric  acid,  borates,  salicylic  acid, 
and  salicylates.  The  use  of  milk  preservatives  is  illegal  in  most  states. 

EXPERIMENTS  ON  MILK 

1.  Reaction. — Test  the  reaction  of  fresh  cow's  milk  to  litmus,  phenolphthalein 
and  Congo  red. 

2.  Biuret  Test. — Make  the  biuret  test  according  to  directions  given  on 
page  100. 

3.  Microscopical  Examination. — Examine  fresh  whole  milk,   skimmed  or 
centrifugated  milk,  and  colostrum  under  the  microscope.    Compare  the  micro- 
scopical appearance  with  Fig.  104,  page  331. 

4.  Specific  Gravity. — Determine  the  specific  gravity  of  both  whole  and 
skimmed  milk  (see  page  342).    Which  possesses  the  higher  specific  gravity? 
Explain  why  this  is  so. 

5.  Film  Formation. — Place  10  c.c.  of  milk  in  a  small  beaker  and  boil  a  few 
minutes.    Note  the  formation  of  a  film.    Remove  the  film  and  heat  again.    Does 
the  film  now  form?    Of  what  substance  is  this  film  composed?    The  biuret  test 
was  positive ;  why  do  we  not  get  a  coagulation  here  when  we  heat  to  boiling? 

6.  Coagulation  Test.— Place  about  5  c.c.  of  milk  hi  a  test-tube,  acidify  slightly 
with  dilute  acetic  acid  and  heat  to  boiling.    Do  you  get  any  coagulation?    Why? 

7.  Action  of  Hot  Alkali. — To  a  little  milk  in  a  test-tube  add  a  few  drops  of 
potassium  hydroxide  and  heat.    A  yellow  color  develops  and  gradually  deepens 
into  a  brown.    To  what  is  the  formation  of  this  color  due?     (See  Moore's  Test, 
Chapter  II.) 

8.  Test  for  Chlorides. — To  about  5  c.c.  of  milk  hi  a  test-tube  add  a  few  drops 
of  very  dilute  nitric  acid  to  form  a  precipitate.    Filter  off  this  precipitate  and  test 
the  filtrate  for  chlorides.    Does  milk  contain  any  chlorides? 

9.  Guaiac  Test. — To  about  5  c.c.  of  water  hi  a  test-tube  add  3  drops  of 
milk  and  enough  alcoholic  solution  of  guaiac  (strength  about  i :  60) l  to  cause 
turbidity.    Thoroughly  mi*  the  fluids  by  shaking  and  observe  any  change  which 
may  gradually  take  place  hi  the  color  of  the  mixture.    If  no  blue  color  appears 
in  a  short  time,  heat  the  tube  gently  below  6o°C.  and  observe  whether  the 
color  reaction  is  hastened.    In  case  a  blue  color  does  not  appear  hi  the  course 
of  a  few  minutes,  add  hydrogen  peroxide  or  old  turpentine,  drop  by  drop,  until 
the  color  is  observed. 

Fresh  milk  will  frequently  give  this  blue  color  when  treated  with  an 
alcoholic  solution  of  guaiac  without  the  addition  of  hydrogen  peroxide 
or  old  turpentine.  Those  milks  which  respond  positively,  fail  to  do  so 
after  boiling  15-20  seconds.  What  substances  beside  milk  respond  to 
this  test?  See  discussion  on  page  261. 

10.  Differentiation  of  Human  and  Cow's  Milk  (Modification  of  Bauer's  Test).1 
— Introduce  2  c.c.  of  fresh  human  milk  into  a  50  c.c.  test-tube  and  2  c.c.  of  fresh 

1  Buckmaster  advises  the  use  of  an  alcoholic  solution  of  guaiaconic  acid  instead  of  an 
alcoholic  solution  of  guaiac  resin.     Guaiaconic  acid  is  a  constituent  of  guaiac  resin. 
*  Bauer:  M onatssch.  f.  KinderheiL,  n,  474,  1912-13. 
22 


338  PHYSIOLOGICAL  CHEMISTRY 

cow's  milk  into  another  similar  tube.  Add  to  the  contents  of  each  tube  i  drop  of 
a  0.25  per  cent  aqueous  solution  of  nile-blue  sulphate  (Griibler).  Shake  the 
tubes  gently  and  permit  them  to  stand  undisturbed  for  10-30  minutes.  The 
milk  assumes  a  bluish  cast  in  each  case.  At  the  end  of  the  lo-minute  interval 
add  10  c.c.  of  ether  to  the  contents  of  each  tube  and  shake  very  thoroughly  for  one 
minute.  The  ether  extracts  the  pigment  from  the  human  milk,  leaving  the  milk 
white.  In  the  case  of  cow's  milk  the  ether  does  not  extract  the  dye  and  the  milk 
remains  bluish  in  color. 

11.  Tests  to  Differentiate  between  Raw  Milk  and  Heated  Milk.— 

(a)  Tricresol  Peroxidase  Reaction  (Kastle) . — The  peroxidase  reaction  of 
milk  is  founded  upon  the  fact  that  small  amounts  of  raw  milk  will  in- 
duce the  oxidation  of  various  leuco  compounds  by  hydrogen  peroxide. 
This  reaction  has  been  used  in  a  practical  way  as  the  most  convenient 
means  of  differ  en  tia  ting  between  raw  milk  and  heated  milk.  Many 
substances  have  been  employed  for  this  purpose,  e.g.,  guaiac,  para- 
phenylenediamine,  ortol,  amidol,  etc.  Kastle  has  found  that  a  dilute 
solution  of  "tricresol"1  acts  as  a  sensitizing  agent  in  the  peroxidase 
reaction  and  offers  the  following  test  which  is  based  upon  this  fact. 

Procedure. — To  2-5  c.c.  of  raw  milk  in  a  test-tube  add  0.1-0.3  c.c.  of  M/io 
hydrogen  peroxide  and  i  c.c.  of  a  i  per  cent  solution  of  "tricresol."  A  slight 
though  unmistakable  yellow  color  will  be  observed  to  develop  throughout  the 
solution.  Repeat  the  test  using  milk  which  has  been  boiled  or  heated  to 
8o°C.  for  10-20  minutes  and  cooled,  and  note  that  no  yellow  color  is  produced. 

The  color  reaction  in  the  case  of  the  raw  milk  probably  results  from 
the  oxidation  of  the  cresols  by  the  hydrogen  peroxide.  The  first 
product  of  this  oxidation2  then  oxidizes  the  leuco  compound,  when  such 
is  present,  and  causes  the  color  observed. 

(6)  Benzidine  Peroxidase  Reaction  (Wilkinson  and  Peters}.3 — To  10  c.c.  of  the 
milk  to  be  tested  add  2  c.c.  of  a  4  per  cent  alcoholic  solution  of  benzidine,  suffi- 
cient acetic  acid  to  coagulate  the  milk  (usually  2-3  drops)  and  finally  2  c.c.  of  a 
3  per  cent  solution  of  hydrogen  peroxide.  Raw  milk  yields  an  immediate  blue 
color.  In  adding  the  peroxide  it  is  best  to  permit  it  to  flow  slowly  down  the 
wall  of  the  vessel  containing  the  mixture  instead  of  allowing  it  to  mix  with  the 
milk.  Milk  which  has  been  heated  to  78°C.  or  above  remains  unchanged. 

The  reduction  of  the  CO2  content  of  milk  through  heating  has  also  been  sug- 
gested as  a  means  of  differentiating  between  raw  and  heated  milk.4 

12.  Saturation  with  Magnesium  Sulphate. — Place  about  5  c.c.  of  milk  in  a 
test-tube  and  saturate  with  solid  magnesium  sulphate.     What  is  this  precipitate? 

13.  Influence  of  Gastric  Rennin  on  Milk. — Prepare  a  series  of  five  tubes  as 
follows : 

1  "Trikresol"  is  the  trade  name  of  an  antiseptic  which  contains  the  three  cresols  in  ap- 
proximately equal  proportions. 

2  Probably  some  organic  peroxide  or  quinoid  compound. 

3  Wilkinson  and  Peters:  Z.  Nahr-Genussm.,  16,  No.  3,  p.  172. 

4  Van  Slyke  and  Keeler:  Jour.  Biol.  Chem.,  42,  41,  1920. 


MILK  339 

(a)  5  c.c.  of  fresh  milk  +  0.2  per  cent  HC1  (add  drop  by  drop  until  a  precipitate 
forms). 

(b)  5  c.c.  of  fresh  milk  +  5  drops  of  rennin  solution.1 

(c)  5  c.c.  of  fresh  milk  -f  10  drops  of  0.5  per  cent  Na2CO3. 

(d)  5  c.c.  of  fresh  milk  -f  10  drops  of  ammonium  oxalate. 

(e)  5  c.c.  of  fresh  milk  +  5  drops  of  0.2  per  cent  HC1. 

Now  to  each  of  the  tubes  (c),  (d)  and  (e)  add  5  drops  of  rennin  solution. 
Place  the  whole  series  of  five  tubes  at  4O°C.  and  after  10-15  minutes  note  what 
is  occurring  hi  the  different  tubes.  Give  a  reason  for  each  particular  result. 

14.  Preparation  of  Casein. — Fill  a  large  beaker  one-third  full  of  skimmed 
(or  centrifugated)  milk  and  dilute  it  with  an  equal  volume  of  water.    Add  dilute 
hydrochloric  acid  until  a  flocculent  precipitate  forms.    Stir  after  each  acidifica- 
tion and  do  not  add  an  excess  of  the  acid  as  the  precipitate  would  dissolve. 
Allow  the  precipitate  to  settle,  decant  the  supernatant  fluid,  and  reserve  it  for 
use  hi  later  (15-18)  experiments.    Filter  off  the  precipitate  of  casern  and  re- 
move the  excess  of  moisture  by  pressing  it  between  filter  papers.    Transfer  the 
casein  to  a  small  beaker,  add  enough  95  per  cent  alcohol  to  cover  it  and  stir  for 
a  few  moments.    Filter,  and  press  the  precipitate  between  filter  papers  to  re- 
move the  alcohol.    Transfer  the  casein  again  to  a  small  dry  beaker,  cover  the 
precipitate  with  ether  and  heat  on  a  water-bath  for  ten  minutes,  stirring  con- 
tinuously.   Filter  (reserve  the  filtrate) ,  and  press  the  precipitate  as  dry  as  possible 
between  filter  papers.    Open  the  papers  and  allow  the  ether  to  evaporate  spon- 
taneously.   Grind  the  precipitate  to  a  powder  hi  a  mortar.    Upon  the  casein 
prepared  hi  this  way  make  the  following  tests : 

(a)  Solubility.— Try  the  solubility  in  water,  sodium  chloride,  dilute  acid  and 
alkali. 

(b)  Mfflon's  Reaction.— Make  the  test  according  to  the  directions  given  on 
page  97. 

(c)  Biuret  Test.— Make  the  test  according  to  directions  given  on  page  99. 

(d)  Glyoxylic  Acid  Reaction  (Hopkins-Cole).— Make  the  test  according  to 
the  directions  given  on  page  98. 

(e)  Unoxidized  Sulphur.— Test  for  unoxidized  sulphur  according  to  the  di- 
rections given  on  page  107.    The  sulphur  content  of  casein  is  rather  low,  e.g., 
about  0.065  Per  cent' 

(f)  Fusion  Test  for  Phosphorus.— Test  for  phosphorus  by  fusion  according  to 
directions  given  on  page  128.    Casein  contains  0.7  per  cent  of  phosphorus. 

15.  Coagulable  Proteins  of  Milk.— Place  the  filtrate  from  the  original  casein 
precipitate  in  a  casserole  and  heat,  on  a  wire  gauze,  over  a  free  flame.    As  the 
solution  concentrates,  a  coagulum  consisting  of  lactalbumin  and  lactoglobulin 
will  form.    Continue  to  concentrate  the  solution  until  the  volume  is  about  one- 
half  that  of  the  original  solution.    Filter  off  the  coagulable  proteins  (reserve  the 
filtrate)  and  test  them  as  follows : 

(a)  Millon's  Reaction.— Make  the  test  according  to  the  directions  given  on 
page  98. 

(b)  Biuret  Test. — Make  the  test  according  to  the  directions  given  on  page  100. 

(c)  Glyoxylic  Acid  Reaction  (Hopkins-Cole).— Make  the  test  according  to 
the  directions  given  on  page  98. 

1  Any  commercial  rennin  or  rennet  preparation  or  an  extract  of  the  gastric  mucosa 
of  the  pig  may  be  employed. 


340  PHYSIOLOGICAL  CHEMISTRY 

16.  Detection  of  Calcium  Phosphate. — Evaporate  the  filtrate  from  the 
coagulable  proteins,  on  a  water-bath,  until  crystals  begin  to  form.  It  may  be 
necessary  to  concentrate  to  15  c.c.  before  any  crystallization  will  be  observed. 
Cool  the  solution,  filter  off  the  crystals  (reserve  the  filtrate),  and  test  them  as 
follows : 

(a)  Microscopical  Examination. — Examine  the  crystals  and  compare  them 
with  those  in  Fig.  no. 

(b)  Dissolve  the  crystals  in  nitric  acid.    Test  part  of  the  acid  solution  for 
phosphates.    Render  the   remainder   of   the   solution   slightly   alkaline   with 

ammonia,  then  acidify  with  acetic  acid  and  add  am- 
monium oxalate.  Examine  the  crystals  under  the 
microscope  and  compare  them  with  those  in  Fig. 
140,  page  476. 

17.  Detection  of  Lactose. — Concentrate  the  fil- 
trate from  the  calcium  phosphate  until  it  is  of  a 
syrup-like  consistency.  Allow  it  to  stand  over  night 
and  observe  the  formation  of  crystals  of  lactose. 
Make  ^  following  experiments.  ' 

(a)  Microscopical  Examination. — Examine  the 
crystals  and  compare  them  with  those  in  Fig.  109,  page  335. 

(b)  Fehling's  Test. — Try  Filing's  test  upon  the  mother  liquor. 

(c)  Phenylhydrazine  Test.— Apply  the  phenylhydrazine  test  to  some  of  the 
mother  liquor  according  to  the  directions  given  on  page  22. 

18.  Milk  Fat. — (a)  Evaporate  the  ether  filtrate  from  the  casein  (Experiment 
13)  and  observe  the  fatty  residue.    The  milk  fat  was  carried  down  with  the 
precipitate  of  casein  and  was  removed  when  the  latter  was  treated  with  ether. 
If  centrifugated  milk  was  used  in  the  preparation  of  the  caseinogen  the  amount 
of  fat  in  the  ether  filtrate  may  be  very  small.    To  secure  a  larger  yield  of  fat 
proceed  according  to  directions  given  under  (b)  below. 

(b)  To  25  c.c.  of  whole  milk  in  an  evaporating  dish  add  a  little  sand  or  filter 
paper  and  evaporate  the  fluid  to  dryness  on  a  water-bath.  Grind  or  break  up 
the  residue  after  cooling  and  extract  with  ether  in  a  flask.  Filter  and  remove 
the  ether  from  the  filtrate  by  evaporation.  How  can  you  identify  fats  in  the 
ethereal  residue? 

19.  Saponification  of  Butter. — Dissolve  a  small  amount  of  butter  in  alcohol 
made  strongly  alkaline  with  potassium  hydroxide.    Place  the  alcoholic-potash 
solution  in  a  casserole,  add  about  100  c.c.  of  water  and  boil  for  10-15  minutes  or 
until  the  odor  of  alcohol  cannot  be  detected.    Place  the  casserole  in  a  hood  and 
neutralize  the  solution  with  sulphuric  acid.    Note  the  odor  of  volatile  fatty  acids, 
particularly  butyric  acid.    Under  certain  conditions  the  odor  of  ethyl  butyrate 
may  also  be  detected. 

20.  Detection  of  Preservatives. — (a)  Formaldehyde.— In  these 
tests  two  controls  should  be  run,  one  with  pure  milk  and  one  with 
milk  to  which  a  very  small  amount  of  formaldehyde  has  been  added. 

I.  Leach's  Hydrochloric  Acid  Test.— Mix  10  c.c.  of  milk  and  10  c.c.  of  con- 
centrated hydrochloric  acid  containing  about  0.002  gram  of  ferric  chloride  in  a 
small  porcelain  evaporating  dish  or  casserole  and  gradually  raise  the  temperature 


MILK 


341 


of  the  mixture,  on  a  water-bath,  nearly  to  the  boiling-point,  with  occasional 
stirring.  If  formaldehyde  is  present  a  violet  color  is  produced,  while  a  brown 
color  develops  in  the  absence  of  formaldehyde.  In  case  of  doubt  the  mixture, 
after  having  been  heated  nearly  to  the  boiling-point  for  about  one  minute, 
should  be  diluted  with  50-75  c.c.  of  water,  and  the  color  of  the  diluted  fluid 
carefully  noted,  since  the  violet  color  if  present  will  quickly  disappear.  For- 
maldehyde may  be  detected  by  this  test  when  present  in  the  proportion  i :  250,000. 

(b)  Salicylic  Acid  and  Salicylates.—Remont's  Method.1— Acidify  20  c.c.  of  milk 
with  sulphuric  acid,  shake  well  to  break  up  the  curd,  add  25  c.c.  of  ether,  mix  thor- 
oughly, and  allow  the  mixture  to  stand.    By  means  of  a  pipette  remove  5  c.c.  of  the 
ethereal  extract,  evaporate  it  to  dryness,  boil  the  residue  with  10  c.c.  of  40  per  cent 
alcohol,  and  cool  the  alcoholic  solution.     Make  the  volume  10  c.c.,  filter  through 
a  dry  paper  if  necessary  to  remove  fat,  and  to  5  c.c.  of  the  filtrate,  which  represents 
2  c.c.  of  milk,  add  2  c.c.  of  a  2  per  cent  solution  of  ferric  chloride.    The  production 
of  a  purple  or  violet  color  indicates  the  presence  of  salicylic  acid. 

This  test  may  form  the  basis  of  a  quantitative  method  by  diluting  the  final 
solution  to  50  c.c.  and  comparing  this  with  standard  solutions  of  salicylic  acid. 
The  colorimetric  comparisons  may  be  made  in  a  Duboscq  colorimeter. 

(c)  Hydrogen  Peroxide. — Add  2-3  drops  of  a  2  percent  aqueous  solution  of 
para-phenylenediamine  hydrochloride  to  10-15  c.c.  of  milk.    If  hydrogen  peroxide 
is  present  a  blue  color  will  be  produced  immediately  upon  shaking  the  mixture  or 
after  allowing  it  to  stand  for  a  few  minutes.    It  is  claimed  that  hydrogen  peroxide 
may  be  detected  by  this  test  when  present  in  the  proportion  i  :  40,000. 

(d)  Boric  Acid  and  Borates. — To  the  ash,  obtained  according  to  the  directions 
given  in  Experiment  4,  page  345,  add  2  drops  of  dilute  hydrochloric  acid  and  i 
c.c.  of  water.     Place  a  strip  of  turmeric  paper  in  the  dish  and  after  allowing  it 
to  soak  for  about  one  minute  remove  it  and  allow  it  to  dry  in  the  air.     The 
presence  of  boric  acid  is  indicated  by  the  production  of  a  deep  red  color  which 
changes  to  green  or  blue  upon  treatment  with  a  dilute  alkali.    This  test  is  sup- 
posed to  show  boric  acid  when  present  in  the  proportion  i  :  8000. 

Quantitative  Analysis  of  Milk 

1 .  Collection  of  Human  Milk  for  Analysis.— There  are  two  methods 
of  obtaining  samples  of  breast  milk  for  analysis.2 

First  Method. — Express  all  the  milk  from  one  breast  and  mfc  thoroughly. 
Second  Method. — Draw  one  ounce  of  milk  before  nursing  and  one  ounce  after 
nursing.  Mix  the  two  samples  throughly.  The  best  time  for  obtaining  samples 
is  9-10  o'clock  in  the  morning. 

2.  Specific  Gravity. — This  may  be  determined  conveniently  by 
means  of  a  Soxhlet,  Veith,  or  Quevenne  lactometer.     A  lactometer 
reading   of    32°  denotes  a  specific  gravity  of  1.032.     The  determina- 
tion should  be  made   at   about   6o°F.   and  the  lactometer  reading 
corrected  by  adding  or  subtracting  0.1°  for  every  degree  F.  above  or 
below  that  temperature. 

1  For  other  tests  see  Sherman's  Organic  Analysis,  Second  Edition,  p:  378. 

2Talbot:  Jour.  Am.  Med.  Ass'n,  73,  662,  1919. 


342 


PHYSIOLOGICAL   CHEMISTRY 


>C.C;: 


3.  Fat.  —  (a)  Babcock's  Centrifugal  Method.1  —  Principle.  —  The 
principle  of  this  method  is  the  destruction  of  organic  matter  other 
than  fat  by  sulphuric  acid  and  the  centrifugation  of  the  acid  solution 
in  the  special  tube  shown  in  Fig.  1  1  1  and  the  subsequent  reading  of 
the  percentage  of  fat  by  means  of  the  tube's  graduated  neck.  The 
method  is  one  of  the  most  satisfactory  in  common  use 
and  is  accurate  to  within  0.5  per  cent. 

Procedure.  —  By  means  of  a  special  narrow  pipette  intro- 
duce milk  into  the  tube  up  to  the  5  c.c.  mark.  Now  add 
sufficient  sulphuric  acid  (sp.  gr.  1.83-1.834)  to  fill  the  body 
of  the  tube  and  rotate  the  tube  to  secure  a  homogeneous 
acid-milk  solution.  Fill  the  neck  of  the  tube  with  an  acid- 
alcohol  mixture.2  Centrifuge  the  tube  and  contents  for  one 
to  two  minutes  and  read  off  the  percentage  of  fat  by  means 
of  the  graduated  neck  of  the  tube.  If  the  top  of  the  fat  column 
is  not  at  zero  it  may  be  brought  there  by  the  addition  of 
water  and  a  moment's  recentrifugation. 

In  case  very  rich  milk  (over  5  per  cent  fat)  is  under  ex- 
animation,  it  may  be  diluted  with  an  equal  volume  of  water 
before  examination  and  the  fat  percentage  multiplied  by  2.  In 
the  examination  of  cream  it  is  customary  to  dilute  the  sample 
with  four  volumes  of  water  and  multiply  the  resultant  fat 
value  by  5. 

(b)  Quantitative  Determination  of  Fat  in  Milk  by  the 
Meigs3  Method  with  Modification  and  Improved  Apparatus 
by  Croll.4—  The  method  as  stated  by  Dr.  Meigs  is:  Approxi- 
mately 10  c.c.  of  milk  is  carefully  weighed  and  transferred  to 
an  ordinary  100  c.c.  glass-stoppered  graduated  cylinder. 
Twenty  c.c.  each  of  distilled  water  and  ether  (0.720)  are 
added,  the  ground-glass  stopper  tightly  inserted  in  the  bottle, 
and  the  whole  shaken  vigorously  for  five  minutes.  Then  the 
bottle  is  carefully  unstoppered,  20  c.c.  95  per  cent  alcohol 
added,  the  stopper  reinserted  and  again  shaken  for  five 
minutes.  The  bottle  is  now  placed  on  a  table  and  the  con- 
tents will  separate  into  two  distinct  strata,  the  upper  of  which  contains  prac- 
tically all  the  fat.  This  stratum  is  carefully  removed  by  a  small  pipette  and 
transferred  to  a  carefully  weighed  glass  evaporating  dish.  The  thin  ether 
layer  remaining  is  washed  by  the  addition  of  5  c.c.  of  ether.  This  is  removed 
by  pipetting  off.  This  washing  is  repeated  four  times.  On  each  addition  the 

1  A  modification  of  this  method  for  use  with  sweetened  dairy  products,  e.g.,  ice  cream, 
and  entailing  the  use  of  a  different  type  of  centrifuge  tube  has  been  proposed  by  Halverson 
(Jour.  Ind.  and  Eng.  Chem.,  5,  403,  1913;.     A  more  recent  modification  involving  the 
use  of  mixtures  of  glacial  acetic,  sulphuric  and  nitric  acids  instead  of  sulphuric  acid  alone 
has  been  proposed  by  Francis  and  Morgan  (Jour.  Ind.  and  Eng.  Chem.,  9,  861,  1917). 
These  authors  use  the  regulation  Babcock  tube,  and  the  method  is  applicable  to  the  analysis 
of  ice  cream,  and  evaporated,  malted  and  dried  milk. 

2  This  mixture  consists  of  equal  volumes  of  amyl  alcohol  and  concentrated  hydrochloric 
acid. 

3  Original  paper  by  Dr.  Arthur  V.  Meigs  in  Philadelphia  Medical  Times,  July  i,  1882. 

4  Croll:  Biochem.  Bull.,  2,  509,  1913. 


FIG.     in. — BAB- 
COCK    TUBE. 


MILK 


343 


sides  of  the  bottle  should  carefully  be  washed  down  by  the  fresh  ether. 
Finally,  the  pipette  is  rinsed  with  a  little  ether.  The  evaporating  dish  with 
contents  is  now  placed  on  a  safety  water-bath  and  the  ether  evaporated. 
The  drying  is  continued  in  a  hot-air  oven  at  a  temperature  below  ioo°C.  and 
finally  completed  in  a  desiccator  to  constant  weight 

CrolTs  modification  consists  of  subsequent  repeated  extraction  of  the  end- 
product  of  evaporation  with  absolute  ether.    The  combined  extracts  are  filtered 
and  the  small  filter  paper  is  washed  repeatedly 
with  absolute  ether.      The  combined  extracts 
and    washings   are   evaporated  and  dried  as 
before  and  then  weighed. 

The  piece  of  apparatus  shown  hi  Fig.  112, 
above  was  also  devised  by  Croll  to  do  away 
with  the  use  of  the  pipette.1  On  closing  the 
top  with  a  finger  and  blowing  into  the  mouth- 
piece, the  upper  stratum  is  forced  out  into  the 
dish.  The  bottle  is  washed  by  simply  pouring 
the  ether  into  the  tube.  This  lessens  the 
possibility  of  accidental  loss. 

The  accuracy  of  the  method  compared  with 
that  of  the  Soxhlet  method,  using  the  paper- 
coil  modification  and  extracting  until  fresh 
portions  of  absolute  ether  gave  no  further 
trace  of  extr  active  material,  is  shown  by  the 
average  diffe  rence  on  twelvesamples  of  human 
milk  being  only  0.017  per  cent  less  than  by  the 
Soxhlet  and  on  seven  samples  cow's  milk  being 
only  0.019  per  cent  less.  The  extreme  differ- 
ences in  case  of  the  human  milk  were — 0.004 
per  cent  and  0.044  Per  cent  ^d  m  case  °f 
the  cow's  milk — 0.006  per  cent  and  — 0.068 
per  cent. 

(c)  Adams'  Paper-coil  Method. — Introduce 
about  5  c.c.  of  milk  into  a  small  beaker,  quickly 
ascertain  the  weight  to  centigrams,  stand  a 
fat-free  coil2  in  the  beaker  and  incline  the  vessel 
and  rotate  the  coil  in  order  to  hasten  the  absorp- 
tion of  the  milk.  Immediately  upon  the  com- 
plete absorption  of  the  milk  remove  the  coil  and  again  quickly  ascertain  the 
weight  of  the  beaker.  The  difference  in  the  weights  of  the  beaker  at  the  two 
weighings  represents  the  quantity  of  milk  absorbed  by  the  coil.  Dry  the  coil 
carefully  at  a  temperature  below  ioo°C.  and  extract  it  with  ether  for  3-5  hours 
in  a  Soxhlet  apparatus  (Fig.  113).  Using  a  safety  water-bath,  heat  the  flask 
containing  the  fat  to  constant  weight  at  a  temperature  below  ioo°C. 

Calculation. — Divide  the  weight  of  fat,  in  grams,  by  the  weight  of  milk,  in 
grams.  The  quotient  multiplied  by  100  is  the  percentage  of  fat  contained  in  the 
milk  examined. 

1  If  desired  a  cork  with  two  tubes  may  be  substituted  for  this  somewhat  complicated 
apparatus. 

2  Very  satisfactory  coils  are  manufactured  by  Schleicher  and  Schull. 


FIG.  112. — CROLL'S  FAT 
APPARATUS 


344 


PHYSIOLOGICAL   CHEMISTRY 


(d)  N  ephelometric  Method  of  Bloor.1 — This  method  is  exactly  similar  in  principle 
and  procedure  to  the  method  given  for  the  determination  of  fat  in  blood.     (See 
page  300.)     One  c.c.  of  milk  is  ordinarily  taken. 

(e)  Approximate  Determination  by  Peter's  Lactoscope. — Milk  is  opaque  mainly 

because  of  the  suspended  fat  globules  and  there- 
fore by  means  of  the  estimation  of  this  opacity 
we  may  obtain  data  as  to  the  approximate  con- 
tent of  fat.  Feser's  lactoscope  (Fig.  114)  may 
be  used  for  this  purpose.  Proceed  as  follows: 
By  means  of  the  graduated  pipette  accompany- 
N  ing  the  instrument  introduce  4  c.c.  of  milk  into 
the  lactoscope.  Add  water  gradually,  shaking 
after  each  addition,  and  note  the  point  at  which 
the  black  lines  upon  the  inner  white  glass 
cylinder  are  distinctly  visible.  Observe  the  point 
on  the  graduated  scale  of  the  lactoscope  which  is 
level  with  the  surface  of  the  diluted  milk.  This 
reading  represents  the  percentage  of  fat  present 
in  the  undiluted  milk.  Pure 
milk  should  contain  at  least  3 
per  cent  of  fat. 

4.  Total  Solids.2— Intro- 
duce 2-5  grams  of  milk  into  a 
weighed  flat-bottomed  plati- 
num dish3  and  quickly  ascer- 
tain the  weight  to  milligrams. 
Expel  the  major  portion  of 
the  water  by  heating  the  open 
dish  on  a  water-bath  and 
continue  the  heating  in  an 
air-bath  or  water  oven  at 
97°-ioo°C.  until  th,e  weight 
is  constant.  (If  platinum 
dishes  are  employed  this 
residue  may  be  used  hi  the 

determination  of  ash  according  to  the  method  described  below.) 

Calculation.4 — Divide  the  weight  of  the  residue,  in  grams,  by  the  weight  of 

milk  used,  in  grams.    The  quotient  is  the  percentage  of  solids  contained  in  the 

milk  examined. 


ID — r 


FIG.    113. — SOXHLET   APPARATUS. 


>II4<_FESER,S 
LACTOSCOPE. 


1  Bloor:  /.  Am.  Chem.  Soc.,  36,  1300,  1914. 

4  ShackelPs  method  for  the  vacuum  desiccation  of  frozen  preparations  may  be  used 
where  great  accuracy  is  desired  (see  American  Journal  of  Physiology,  24,  325,  1909). 

3  Lead  foil  dishes,  costing  only  about  one  dollar  per  gross,  make  a  very  satisfactory 
substitute  for  the  platinum  dishes. 

4  The  percentage  of  total  solids  may  be  calculated  from  the  specific  gravity  and  percentage 
of  fat  by  means  of  the  following  formula  which  has  been  proposed  by  Richmond: 

8=0.25  L+i. 2  F+o.14 
S  =  total  solids. 
L«=  lactometer  reading. 
F«=fat  content. 


MILK  345 

5.  Ash. — Heat  the  dry  solids  from  2-5  grams  of  milk,  obtained  according  to 
the  method  just  given,  over  a  very  low  flame1  until  a  white  or  light  gray  ash  is 
obtained.    Cool  the  dish  in  a  desiccator  and  weigh.     (This  ash  may  be  used  hi 
testing  for  borates  according  to  directions  on  page  341.) 

6.  Proteins:  Nephelometric    Determination    of    Proteins,     Casein, 
Globulin,  and  Albumin  in  Milk.     Method  of  Kober.2 — Principle. — The 
proteins  are  precipitated  with  sulphosalicylic  acid  and  the  precipitate 
estimated  nephelometrically  (see  discussion  of  nephelometric  methods, 
page  294). 

Procedure. — Five  c.c.  of  milk  are  carefully  measured  into  a  250  c.c.  flask 
and  after  adding  200  c.c.  of  distilled  water  and  10  c.c.  of  decinormal  sodium 
hydroxide  solution,  water  is  added  to  the  mark  and  the  mixture  shaken.  Ten 
c.c.  are  put  with  exactly  2  c.c.  of  ether  in  a  centrifuge  tube  which  is  then  tightly 
stoppered  with  a  cork  and  vigorously  shaken.  Allow  to  separate  and  withdraw 
5  c.c.  of  the  aqueous  layer  without  contamination  with  ether.  Dilute  to  50  c.c. 
Take  10  c.c.  of  this  solution  and  add  10  c.c.  of  3  per  cent  sulphosalicylic  acid.  A 
suspension  of  casein  is  obtained  which  can  be  matched  accurately  with  the 
following  standard :  i  volume  (5  c.c.)  of  a  o.oi  per  cent  casein  solution3  to  which 
is  added  2  volumes  (10  c.c.)  of  3  per  cent  sulphosalicylic  acid. 

The  protein  obtained  with  this  reagent  is  not  all  casein,  and  hi  order  to  obtain 
the  exact  amount  of  casein  the  casein  is  precipitated  according  to  the  "official 
method'1  or  the  method  of  Hart  given  below  and  the  amount  of  precipitate  ob- 
tained hi  an  aliquot  portion  of  the  filtrate,  by  adding  4  volumes  of  the  reagent, 
is  determined  nephelometrically.  This  fraction,  for  want  of  a  better  name  called 
the  "globulin  and  albumin  fraction,"  is  subtracted  from  the  gross  casein,  to 
give  the  amount  of  casein  precipitated  by  the  "official  method." 

The  ether  used  in  extracting  the  fat  increases  the  volume  of  the  solution  and 
hence  a  factor  allowing  for  this  must  be  used.  For  10  c.c.  of  diluted  milk  and 
2  c.c.  of  ether  the  factor  is  0.910. 

7.  Proteins.— Introduce  a  known  weight  of  milk  (5-10  grams)  into  a  500  c.c. 
Kjeldahl  digestion  flask  and  add  20  c.c.  of  concentrated  sulphuric  acid  and  about 
0.2  gram  of  copper  sulphate.    Expel  the  major  portion  of  the  water  by  heating 
over  a  low  flame  and  finally  use  a  full  flame  and  allow  the  mixture  to  boil  one  to 
two  hours.    Complete  the  determination  according  to  the  directions  given  under 
Kjeldahl  Method,  page  504. 

Calculation.  —Multiply  the  total  nitrogen  content  by  the  factor  6.37 4  to  obtain 
the  protein  content  of  the  milk  examined. 

1  Great  care  should  be  used  in  this  ignition,  the  dish  at  no  time  being  heated  above  a 
faint  redness,  as  chlorides  may  volatilize. 

2  Kober:  /.  Am.  Chem.  Soc.,  35,  1585,  1913. 

3  Standard  Casein  Solution. — Dissolve  with  stirring  o.i  gram  of  casein  or  its  equivalent 
in  i  c.c.  of  o.i  N  NaOH,  add  95  c.c.  of  distilled  water,  add  2  c.c.  of  toluene,  shake  thoroughly 
and  make  up  to  100  c.c.     This  is  the  stock  solution  which  keeps  three  or  four  days  or  longer. 
The  standard  solution  is  made  up  fresh  every  day  by  making  10  c.c.  of  the  stock  solution 
up  to  100  c.c.  with  water.     The  standard  is  controlled  by  total  nitrogen  estimations  using 
the  factor  6.38  for  casein. 

4  The  usual  factor  employed  for  the  calculation  of  protein  from  the  nitrogen  content  is 
6.25  and  is  based  on  the  assumption  that  proteins  contain  on  the  average  16  per  cent  of 
nitrogen.    This  special  factor  of  6.37  is  used  to  calculate  the  protein  content  from  the  total 
nitrogen,  since  the  principal  protein  constituents  of  milk,  i.e.,  casein  and  lactalbumin, 
contain  about  15.7  per  cent  of  nitrogen. 


346  PHYSIOLOGICAL    CHEMISTRY 

8.  Hart's  Casein  Method.1  —  Introduce  10.5  c.c.  of  milk  into  a  200  c.c.  Erlen- 
meyer  flask  and  add  75  c.c.  of  distilled  water  and  1-1.5  c-c-  of  10  per  cent  acetic 
acid.2    Mix  the  contents  by  giving  the  flask  a  vigorous  rotary  motion.    The 
precipitated  casein  is  now  filtered  off  upon  a  9-11  cm.  filter  paper.3    Wash  out 
the  adsorbed  and  loosely  combined  acetic  acid  by  means  of  cold  water.    Con- 
tinue the  washing  of  both  the  casein  on  the  filter  and  that  adhering  to  the  flask, 
until  the  wash  water  has  reached  a  volume  of  at  least  250  c.c. 

Now  return  the  precipitate  and  paper  to  the  original  Erlenmeyer  flask,  add 
75-80  c.c.  of  neutral  (carbon  dioxide-free)  water,  10  c.c.  of  N/io  potassium  hy- 
droxide and  a  few  drops  of  phenolphthalein.  Stopper  the  flask  and  shake  it 
vigorously,  by  hand  or  machine,  until  the  casein  has  been  brought  into  solution.4 
Rinse  the  stopper  with  neutral  (carbon  dioxide-free)  water  and  titrate  the  alka- 
line casein  solution  at  once  with  N/io  hydrochloric  acid  until  there  is  a  dis- 
appearance of  all  red  color.6 

Calculation.  —  Subtract  the  corrected5  acid  reading  from  the  10  c.c.  of  alkali 
used.  The  difference  is  the  percentage  of  casein  in  the  milk.  For  example,  if 
it  takes  6.7  c.c.  of  N/io  hydrochloric  acid  to  titrate  the  alkaline  solution  to  the 
end  point  and  the  check  test  was  equivalent  to  20  c.c.  N/io  acid  the  casein  value 
would  be  obtained  as  follows  : 

10  —  (6.7+0.2)  =3.1  per  cent  casern 

9.  Casein.  —  Mix  about  20  grams  of  milk  with  40  c.c.  of  a  saturated  solution 
of  magnesium  sulphate  and  add  the  salt  in  substance  until  no  more  will  dissolve. 
The  precipitate  consists  of  casein  admixed  with  a  little  fat  and  lacto-globulin. 
Filter  off  the  precipitate,  wash  it  thoroughly  with  a  saturated  solution  of  magnesium 
sulphate,6  transfer  the  filter  paper  and  precipitate  to  a  Kjeldahl  digestion  flask,  and 
determine  the  nitrogen  content  according  to  the  directions  given  in  a  previous 
experiment  (6). 

Calculation.  —  Multiply  the  total  nitrogen  by  the  factor  6.37  to  obtain  the  casein 
content. 

10.  Lactalbumin.  —  To  the  filtrate  and  washings  from  the  determination  of 
casein,  in  Experiment  8,  add  Almen's7  reagent  until  no  more  precipitate  forms. 
Filter  off  the  precipitate  and  determine  the  nitrogen  content  according  to  the  direc- 
tions given  under  Proteins,  page  345. 

Calculation.  —  Multiply  the  total  nitrogen  by  the  factor  6.37  to  obtain  the  lactal- 
bumin  content. 

11.  Lactose.  —  To  about  350  c.c.  of  water  in  a  beaker  add  20  grams  of  milk, 
thoroughly,  acidify  the  fluid  with  about  2  c.c.  of  10  per  cent  acetic  acid  and 


1Hart:  Jour.  Biol.  Chem.,  6,  445,  1909. 

2  In  general  1.5  c.c.  of  acetic  acid  gives  a  clear  solution  which  filters  nicely  but  occasion- 
ally, when  the  milk  has  a  low  casein  value  it  is  advisable  to  use  less  acetic  acid. 

3  The  process  of  nitration  may  be  retarded  through  the  packing  of  the  casein  mass 
upon  the  filter  paper.     In  this  case  conduct  a  fine  stream  of  cold  water  against^the  upper 
point  of  contact  of  filter  paper  and  casein.     By  this  means  the  casein  precipitate  is  loosened 
and  gathers  in  the  apex  of  the  filter.     This  procedure  is  very  essential.     It  is  not  necessary 
to  remove  the  casein  which  adheres  to  the  interior  of  the  flask. 

4  Solution  is  indicated  by  the  disappearance  of  the  white  casein  particles  which  would 
otherwise  settle  to  the  bottom  of  the  flask. 

5  A  check  test  should  be  run  parallel  with  the  entire  determination.     Even  with  special 
precautions  as  to  neutrality,  it  is  generally  found  that  an  acid  check  of  0.2-0.3  will  be 
obtained.     This  check  titration  should  be  added  to  the  volume  of  acid  used  in  titration. 

6  Preserve  the  filtrate  and  washings  for  the  determination  of  lactalbumin  (Expt.  10). 

7  Almen's  reagent  may  be  prepared  by  dissolving  5  grams  of  tannic  acid  in  240  c.c.  of 
50  per  cent  alcohol  and  adding  10  c.c.  of  25  per  cent  acetic  acid. 


MILK  347 

stir  the  acidified  mixture  continuously  until  a  flocculent  precipitate  forms.  At 
this  point  the  reaction  should  be  distinctly  acid  to  litmus.  Heat  the  solution  to 
boiling  for  one-half  hour,  filter,  rinse  the  beaker  thoroughly,  and  wash  the  pre- 
cipitated proteins  and  the  adherent  fat  with  hot  water.  Combine  the  filtrate 
and  wash  water  and  concentrate  the  mixture  to  about  150  c.c.  Cool  the  solution 
and  dilute  it  to  200  c.c.  in  a  volumetric  flask.  Titrate  this  sugar  solution  accord- 
ing to  directions  given  under  Fehling's  Method,  page  541,  or  Benedict's  Method, 
page  538. 

Myers1  recommends  the  following  procedure  for  the  determination  of  lactose 
in  milk.  One  part  of  milk  is  mixed  with  an  equal  volume  of  phosphotungstic 
acid  solution  (70.0  grams  acid  and  200  c.c.  cone.  HC1  in  i  liter  of  water)  and  2-3 
parts  of  water.  Mix  well,  filter  until  clear,  and  titrate  the  clear  filtrate  against 
Benedict's  solution  (25  c.c.  reduced  by  67  mg.  of  lactose). 

The  milk  ^ay  also  be  clarified  for  the  lactose  determination  by  means  of 
aluminum  nydroxide2  or  dialyzed  iron.3  The  dialyzed  iron  procedure  is  as 
follows :  Dilute  10  gm.  of  milk  to  25  c.c.  and  add  about  3  c.c.  of  10  per  cent  col- 
loidal iron  solution  adding  the  last  portion  drop  by  drop  to  determine  the  exact 
amount  necessary.  Filter  and  wash  with  water  to  make  the  clear  filtrate  100  c.c. 
Titrate  using  Benedict's  method  (see  page  538). 

The  preparation  of  aluminum  hydroxide  cream  and  its  use  in  protein  re- 
moval are  described  under  Nitrogen  Partition,  p.  506,  Chapter  XXVII. 

Calculation. — Make  the  calculation  according  to  directions  given  under 
Fehling's  Method,  page  541,  bearing  in  mind  that  100  c.c.  of  Fehling's  solution 
is  completely  reduced  by  0.0676  gram  of  lactose.4 

1  Myers:  Munch,  med.  Woch.,  59,  1494,  1912. 
1  Welker  and  Marsh:  /.  Am.  Chem.  Soc.,  35,  823,  1913. 
'Hill:  Jour.  Biol.  Chem.,  20,  175,  1915. 

4  In  case  Benedict's  method  is  used  it  should  be  remembered  that  25  c.c.  of  the  reagent 
is  reduced  by  0.067  gram  of  lactose. 


CHAPTER  XIX 


EPITHELIAL  AND  CONNECTIVE  TISSUES 
TEETH 

Epithelial  Tissue  (Keratin).— The  albuminoid  keratin  constitutes 
the  major  portion  of  hair,  horn,  hoof,  feathers,  nails,  and  the  epidermal 
layer  of  the  skin.  There  is  a  group  of  keratins  the  members  of  which 
possess  very  similar  properties.  The  keratins  as  a  group  are  insoluble 
in  the  usual  protein  solvents  and  are  not  acted  upon  by  the  gastric 
or  pancreatic  juices.  They  all  respond  to  the  xanthoproteic  and  Millon 
reactions  and  are  characterized  by  containing  large  amounts  of  sulphur. 
Keratin  from  any  of  its  sources  may  be  prepared  in  a  pure  form  by 
treatment,  in  sequence,  with  artificial  gastric  juice,  artificial  pancreatic 
juice,  boiling  alcohol,  and  boiling  ether,  from  twenty-four  to  forty- 
eight  hours  being  devoted  to  each  process. 

The  percentage  composition  of  some  typical  keratins  is  given  in  the 
following  table: 


Source 

Percentage  composition 

S           N 

c 

H 

0 

Nai 

[5!   

2.80. 

17-51 

51.00 

6.94 

21.75 

Hor 

CO 

ri 

ns                               

3  .  20 

50.86 

6.94 

Indian                                       

4.82 

15.40 

44-06 

6.53 

29.19 

4.96 

14.64 

42.99 

5.9i 

31-50 

4.84 

14.90 

43.85 

6-37 

30.04 

Caucasian  (adults)  

5.22 

15.79 

44.49 

6.44 

28.66 

Caucasian  (children) 

4-93 

14.58 

43-23 

6.46 

30.80 

The  composition  of  human  hair  is  influenced  by  its  color  and  by  the 
race,  sex,  age  and  purity  of  breeding  of  the  individual.3    It  may  be  dif- 

1  Mulder:  Versuch  einer  allgem.  physiol.  Chem.,  Braunschweig,  1844-51. 
*Horbaczewski:  Ladenburg's  Hand-worterbuch  d.  Chem.,  3. 
»  Rutherford  and  Hawk:  Jour.  Biol.  Chem.,  3,  459,  1907. 

348 


EPITHELIAL  AND   CONNECTIVE   TISSUES  349 

ferentiated  from  all  other  animal  hair  or  wool  by  its  high  content  of 
cystine.     Human  hair  may  yield  nearly  12  per  cent  of  this  ammo-acid.1 

EXPERIMENTS  ON  EPITHELIAL  TISSUE 
Keratin 

Horn  shavings  or  nail  parings  may  be  used  in  the  experiments  which 
follow: 

1.  Solubility.— Test  the  solubility  of  keratin  in  water,  dilute  and  concentrated 
acid  and  alkali. 

2.  Millon's  Reaction. 

3.  Xanthoproteic  Reaction. 

5.  Glyoxylic  Acid  Reaction  (Hopkins-Cole). 

6.  Test  for  Unoxidized  Sulphur. 

CONNECTIVE  TISSUE 
I.  WHITE  FIBROUS  TISSUE 

The  principal  solid  constituent  of  white  fibrous  connective  tissue 
is  the  albuminoid  collagen.  This  body  is  also  found  in  smaller  per- 
centage in  cartilage,  bone,  and  ligament,  but  the  collagen  from  the 
various  sources  is  not  identical  in  composition.  In  common  with  the 
keratins,  collagen  is  insoluble  in  the  usual  protein  solvents.  It  differs 
from  keratin  in  containing  less  sulphur.  One  of  the  chief  character- 
istics of  collagen  is,  according  to  Hofmeister,  the  property  of  being 
hydrolyzed  by  boiling  acid  or  water  with  the  formation  of  gelatin. 
Emmett  and  Gies2  claim  that  under  these  conditions  there  is  an  intra- 
molecular rearrangement  of  collagen  and  the  resultant  gelatin  is  conse- 
quently not  the  product  of  hydrolysis.  The  liberation  of  ammonia  from 
the  collagen  during  the  process  apparently  confirms  this  view.  Collagen 
gives  Millon's  reaction  as  well  as  the  xanthoproteic  and  biuret  tests. 

The  form  of  white  fibrous  tissue  most  satisfactory  for  general  ex- 
periments is  the  tendo  Achillis  of  the  ox.  According  to  Buerger  and 
Gies3  the  fresh  tissue  has  the  following  composition: 

Water 62.87% 

Solids 37.13 

Inorganic  matter 0.47 

Organic  matter. 36.66 

Fatty  substance  (ether-soluble) i  .04 

Coagulable  protein 0.22 

Mucoid .» . . . .1 . 28 

Elastin i .  63 

Collagen 31-59 

Extractives,  etc 0.90 

1  Buchtala:  Zeit.  physiol.  Chem.,  85,  246,  1913. 

8  Emmett  and  Gies:  Jour.  Biol.  chem.,  3,  xxxiii  (Proceedings),  1907. 

1  Buerger  and  Gies:  Am.  Jour.  Physiol.,  6,  219,  1901. 


350  PHYSIOLOGICAL   CHEMISTRY 

The  mucoid  just  mentioned  is  called  tendomucoid1  and  is  a  glyco- 
protein.  It  possesses  properties  similar  to  those  of  other  connective- 
tissue  mucoids,  e.g.,  osseomucoid  and  chondromucoid. 

Gelatin,  the  body  which  results  from  the  hydrolysis  of  collagen 
(see  statement  of  Emmett  and  Gies,p.  349),  is  sometimes  classed  as  an 
albuminoid  (see  Chapter  V).  It  responds  to  nearly  all  the  protein 
tests.  It  differs  from  the  keratins  and  collagen  in  being  easily  digested 
and  absorbed.  Gelatin  is  not  a  satisfactory  substitute  for  the  protein 
constituents  of  a  normal  diet,  however,  since  a  certain  portion  of  its 
nitrogen  is  not  available  for  the  uses  of  the  organism.  Gelatin  from 
cartilage  differs  from  gelatin  from  other  sources  in  containing  a  lower 
percentage  of  nitrogen.  Tyrosine  and  tryptophane  are  not  numbered 
among  the  decomposition  products  of  gelatin,  hence  it  does  not  respond 
to  Millon's  reaction  or  the  glyoxylic  acid  reaction.  Cystine  is  also 
absent. 

EXPERIMENTS  ON  WHITE  FIBROUS  TISSUE 

The  Undo  Achillis  of  the  ox  may  be  taken  as  a  satisfactory  type  of 
the  white  fibrous  connective  tissue. 

1.  Preparation  of  Tendomucoid.— Dissect  away  the  fascia  from  about  the 
tendon  and  cut  the  clean  tendon  into  small  pieces.    Wash  the  pieces  in  running 
water,  subjecting  them  to  pressure  in  order  to  remove  as  much  as  possible  of 
the  soluble  protein  and  inorganic  salts.    This  washing  is  very  important.    Trans- 
fer the  washed  pieces  of  tendon  to  a  flask  and  add  300  c.c.  of  half -saturated  lime 
water.2    Shake  the  flask  at  intervals  for  twenty-four  hours.    Filter  off  the  pieces 
of  tendon  and  precipitate  the  mucoid  with  dilute  hydrochloric  acid.    Allow  the 
mucoid  precipitate  to  settle,  decant  the  supernatant  fluid  and  filter  the  remainder. 
Test  the  mucoid  as  follows : 

(a)  Solubility. — Try  the  solubility  in  water,  sodium  chloride,  dilute  and  con- 
centrated acid  and  alkali. 

(b)  Biuret  Test. — First  dissolve  the  mucoid  in  potassium  hydroxide  solution 
and  then  add  a  dilute  solution  of  copper  sulphate. 

(c)  Test  for  Unoxidized  Sulphur. 

(d)  Hydrolysis  of  Tendomucoid. — Place  the  remainder  of  the  mucoid  in  a 
small  beaker,  (add  about  30  c.c.  of  water  and  2  c.c.  of  dilute  hydrochloric  acid 
and  boil  until  the  solution  becomes  dark  brown.    Cool  the  solution,  neutralize 
it  with  concentrated  potassium  hydroxide,  and  test  by  Fehling's  test.    With  a 
reduction  of  Fehling's  solution  and  a  positive  biuret  test  what  do  you  conclude 
regarding  the  nature  of  tendomucoid? 

2.  Collagen. — This   substance  is  present  in  the  tendon  to  the  extent  of 
about  32  per  cent.    Therefore  in  making  the  following  tests  upon  the  pieces  of 


1  Cutter  and  Gies:  Am.  Jour.  PhysioL,  6,  155,  1901. 

2  Made  by  mixing  equal  volumes  of  saturated  lime  w 


water  and  water  from  the  faucet. 


EPITHELIAL  AND   CONNECTIVE   TISSUES  351 

tendon  from  which  the  mucoid,  soluble  protein,  and  inorganic  salts  were  removed 
in  the  last  experiment,  we  may  consider  the  tests  as  being  made  upon  collagen. 

(a)  Solubility. — Cut  the  collagen  into  very  fine  pieces  and  try  its  solubility 
in  water  and  dilute  and  concentrated  acid  and  alkali. 

(b)  Millon's  Reaction. 

(c)  Biuret  Test. 

(d)  Xanthoproteic  Reaction. 

(e)  Glyoxylic  Acid  Reaction  (Hopkins-Cole). 

(f)  Test  for  Unoxidized  Sulphur. — Take  a  large  piece  of  collagen  in  a  test- 
tube  and  add  about  5  c.c.  of  potassium  hydroxide  solution.    Heat  until  the  col- 
lagen is  partly  decomposed,  then  add  1-2  drops  of  lead  acetate  and  again  heat  to 
boiling. 

(g)  Formation  of  Gelatin  from  Collagen. — Transfer  the  remainder  of  the 
pieces  of  collagen  to  a  casserole,  fill  the  vessel  about  two-thirds  full  of  water 
and  boil  for  several  hours,  adding  water  at  Intervals  as  needed.    By  this  means 
the  collagen  is  transformed  and  a  body  known  as  gelatin  is  produced  (see  page 
350). 

3.  Gelatin. — On  the  gelatin  formed  from  the  transformation  of  collagen  in 
the  above  experiment  (g),  or  on  gelatin  furnished  by  the  instructor  make  the 
following  tests : 

(a)  Solubility. — Try  the  solubility  in  the  ordinary  solvents  (see  page  22) 
and  in  hot  water. 

(b)  Millon's  Reaction. 

(c)  Glyoxylic  Acid  Reaction  (Hopkins-Cole). — Conduct  this  test  according 
to  the  modification  given  on  page  106. 

(d)  Test  for  Unoxidized  Sulphur. 

Make  the  following  tests  upon  a  solution  of  gelatin  in  hot  water : 

(a)  Precipitation  by  Mineral  Acids. — Is  it  precipitated  by  strong  mineral  acids 
such  as  concentrated  hydrochloric  acid? 

(b)  Salting-out  Experiment. — Saturate  a  little  of  the  solution  with  solid 
ammonium   sulphate.    Is   the   gelatin   precipitated?    Repeat  the  experiment 
with  sodium  chloride.    What  is  the  result? 

(c)  Precipitation  by  Metallic  Salts. — Is  it  precipitated  by  metallic  salts  such 
as  copper  sulphate,  mercuric  chloride,  and  lead  acetate? 

(d)  Coagulation  Test. — Does  it  coagulate  upon  boiling? 

(e)  Precipitation  by  Alkaloidal  Reagents. — Is  it  precipitated  by  such  reagents 
as  picric  acid,  tannic  acid,  and  trichloracetic  acid? 

(f)  Biuret  Test.— Does  it  respond  to  the  biuret  test? 

(g)  Precipitation  by  Alcohol. — Fill  a  test-tube  one-half  full  of  95  per  cent 
alcohol  and  pour  in  a  small  amount  of  concentrated  gelatin  solution.    Do  you 
get  a  precipitate?    How  would  you  prepare  pure  gelatin  from  the  tendo  Achillis 
of  the  ox? 


II.  YELLOW  ELASTIC  TISSUE  (ELASTIN) 

The  ligamentum  nuchce  of  the  ox  may  be  taken  as  a  satisfactory  type 
of  the  yellow  elastic  connective  tissue.  The  principal  solid  con- 
stituent of  this  tissue  is  elastin,  a  member  of  the  albuminoid  group. 


352  PHYSIOLOGICAL  CHEMISTRY 

In  common  with  the  keratins  and  collagen,  elastin  is  an  insoluble  body 
and  gives  the  protein  color  reactions.  It  differs  from  keratin  prin- 
cipally in  the  fact  that  it  may  be  digested  by  enzymes  and  that  it 
contains  a  very  small  amount  of  sulphur. 

It  has  been  demonstrated  that  elastin  has  the  property  of  absorb- 
ing pepsin  from  the  gastric  juice  and  thus  protecting  it  so  the  enzyme 
can  function  later  in  the  intestine1  (see  Chapter  on  Gastric  Digestion). 

Yellow  elastic  tissue  also  contains  mucoid  and  collagen  but  these  are 
present  in  much  smaller  amount  than  in  white  fibrous  tissue,  as  may  be 
seen  from  the  following  percentage  composition  of  the  fresh  ligamentum 
nuchce  of  the  ox  as  determined  by  Vandegrift  and  Gies.2 

Water 57-57% 

Solids 42 . 43 

Inorganic  matter o. 47 

Organic  matter . .  '41 . 96 

Fatty  substance  (ether-soluble) 1.12 

Coagulable  protein 0.62 

Mucoid 0.53 

Elastin 31.67 

Collagen 7 . 23 

Extractives,  etc o .  80 


EXPERIMENTS  ON  ELASTIN 

1.  Preparation  of  Elastin  (Richards  and  Gies).3— Cut  the  ligament  into  fine 
strips,  run  it  through  a  meat  chopper  and  wash  the  finely  divided  material  in  cold, 
running  water  for  24-48  hours.    Add  an  excess  of  half-saturated  lime  water, 
(see  note  at  the  bottom  of  page  350)  and  allow  the  hashed  ligament  to  extract 
for  48-72  hours.    Decant  the  lime  water,  remove  all  traces  of  alkali  by  washing 
in  water  and  then  boil  in  water  with  repeated  renewals  until  only  traces  of  protein 
material  can  be  detected  in  the  wash  water.    Decant  the  fluid  and  boil  the  liga- 
ment in  10  per  cent  acetic  acid  for  a  few  hours.    Treat  the  pieces  with  5  per  cent 
hydrochloric  acid  at  room  temperature  for  a  similar  period,  extract  again  in 
hot  acetic  acid  and  in  cold  hydrochloric  acid.    Wash  out  traces  of  acid  by  means 
of  water  and  then  thoroughly  dehydrate  by  boiling  alcohol  and  boiling  ether 
in  turn.    Dry  in  an  air-bath  and  grind  to  a  powder  in  a  mortar. 

2.  Solubility.— Try  the  solubility  of  the  finely  divided  elastin,  prepared  by 
yourself  or  furnished  by  the  instructor,  in  the  ordinary  solvents  (see  page  22). 
How  does  its  solubility  compare  with  that  of  collagen? 

3.  Millon's  Reaction. 

4.  Xanthoproteic  Reaction. 

5.  BiuretTest. 

6.  Glyoxylic  Acid  Reaction  (Hopkins-Cole).— Conduct  this  test  according  to 
the  modification  given  on  page  106. 

7.  Test  for  Unoxidized  Sulphur. 

1  Abderhalden  and  Meyer:  Zeit.  physiol.  Chem.,  74,  67,  1911. 

2  Vandegrift  and  Gies:  Am.  Jour.  Physiol.,  5,  287,  1901. 
8  Richards  and  Gies:  Am.  Jour.  Physiol.,  7,  93,  1902. 


EPITHELIAL  AND   CONNECTIVE  TISSUES      f  353 

III.  CARTILAGE 

The  principal  solid  constituents  of  the  matrix 'of  cartilaginous  tissue 
are  chondromucoid,   chondroitin-sulphuric  acid,   chondroalbumoid    and 
collagen.     Chondromucoid   differs   from    the   mucoids   isolated   from 
other  connective  tissues  in  the  large  amount  of  chondroitin-sulphuric 
acid    obtained    upon    decomposition.     Besides    being    an    important 
constituent  of  all  forms  of  cartilage,  chondroitin-sulphuric  acid  has 
been  found  in  bone,  ligament,  the  mucosa  of  the  pig's  stomach,  the 
kidney  of  the  ox,  the  inner  coats  of  large  arteries  and  in  human  urine. 
It  may  be  decomposed  through  the  action  of  acid  and  yields  a  nitro- 
genous body  known  as  chondroitin  and  later  this  body  yields  chondrosin. 
Chondrosin  is  also  a  nitrogenous  body  and  has  the  power  of  reducing 
Fehling's  solution  more  strongly  than  dextrose.    Levene  and  La  Forge1 
claim  the  reducing  action  of  chondrosin  to  be  due  to  an  hexosamine 
isomeric  with  glucosamine.     Sulphuric  acid  is  a  by-product  in  the  forma- 
tion of  chondroitin,  and  acetic  acid  is  a  by-product  in  the  formation  of 

chondrosin. 

Chondroalbumoid  is  similar  in  some  respects  to  elastin  and  keratin. 
It  differs  from  keratin  in  being  soluble  in  gastric  juice  and  in  containing 
considerably  less  sulphur  than  any  member  of  the  keratin  group.  It 
gives  the  usual  protein  color  reactions. 

EXPERIMENTS  ON  CARTILAGE 

1.  Preparation  of  the  Cartilage.— Boil  the  trachea  of  an  ox  in  water  until 
the  cartilage  rings  may  be  completely  freed  from  the  surrounding  tissue.    Use 
the  cartilage  so  obtained  in  the  following  experiments : 

2.  Solubility.— Cut  one  of  the  rings  into  very  small  pieces  and  try  the  solubility 
of  the  cartilage  in  water  and  dilute  and  concentrated  acid  and  alkali. 

3.  Mfflon's  Reaction. 

4.  Xanthoproteic  Reaction. 

5.  Glyoxylic  Acid  Reaction  (Hopkins-Cole). -Conduct  this  test  according  to 
the  modification  given  on  page  106. 

6.  Test  for  Unoxidized  Sulphur. 

7  Preparation  of  Cartilage  Gelatin.-Cut  the  remaining  cartilage  rings 
into  small  pieces,  place  them  in  a  casserole  with  water  and  boil  for  several  hours. 
Filter  while  the  solution  is  still  hot.  Observe  that  the  filtrate  soon  becomes  more 
or  less  solid.  What  is  the  reason  for  this?  Bring  a  portion  of  the  material  into 
solution  by  heat  and  try  the  following  tests : 

(a)  Biuret  Test. 

(b)  Test  for  Unoxidized  Sulphur. 

(c)  To  about  5  c.c.  of  the  solution  in  a  test-tube  add  a  few  drops  of  banum 
chloride.    Do  you  get  a  precipitate,  and  if  so  to  what  is  the  precipitate  due? 

i  Levene  and  La  Forge:  Proc.  Soc.  ep.  Biol.  and  Med.,  n,  124,  1914- 

23 


354 


PHYSIOLOGICAL  CHEMISTRY 


(d)  To  about  5  c.c.  of  the  solution  in  a  test-tube  add  a  few  drops  of  dilute 
hydrochloric  acid  and  boil  for  a  few  moments.    Now  add  a  little  barium  chloride 
to  this  solution.    Is  the  precipitate  any  larger  than  that  obtained  in  the  preceding 
experiment?    Why? 

(e)  To  the  remainder  of  the  solution  add  a  little  dilute  hydrochloric  acid  and 
boil  for  a  few  moments.     Cool  the  solution,  neutralize  with  solid  potassium 
hydroxide,  and  try  Fehling's  test.    Explain  the  result. 


IV.  OSSEOUS  TISSUE 

Of  the  solids  of  bone  about  equal  parts  are  organic  and  inorganic 
matter.  The  organic  portion,  called  ossein,  may  be  obtained  by  re- 
moving the  inorganic  salts  through  the  medium  of  dilute  acid.  Ossein 
is  practically  the  same  body  which  is  termed  collagen  in  the  other 
connective  tissues,  and  in  common  with  collagen  yields  gelatin  upon 
being  boiled  with  dilute  mineral  acid. 

In  common  with  the  other  connective  tissues  bone  contains  a 
mucoid  and  an  albuminoid.  Because  of  their  origin  these  bodies  are 
called  osseomucoid  and  osseoalbumoid.  Osseomucoid,  when  boiled  with 
hydrochloric  acid,  yields  sulphuric  acid  and  a  substance  capable  of 
reducing  Fehling's  solution.  The  composition  of  osseomucoid  is  very 
similar  to  that  of  tendomucoid  and  chondromucoid  (see  page  112). 

The  inorganic  basis  of  the  dry,  fat-free  bone  is  a  chemical  substance, 
not  a  mixture.  This  fact  is  indicated  by  the  uniform  composition  of 
the  bones  of  fasting  animals  as  well  as  by  the  definite  relationship  exist- 
ing between  the  elements  present.  Bones  of  normal  and  fasting  animals 
of  the  same  species  present  no  profound  differences  in  percentage  com- 
position. The  percentage  composition  of  the  dry,  fat-free  femurs  of  two 
dogs1  after  the  animals  had  fasted  for  104  and  14  days  respectively  was 
as  follows: 


Dog  No. 

Length  of  fast 

Ash 

N 

CaO 

MgO 

P206 

i. 

104  days 

61.50 

4-6 

33-3 

0.8 

12.80 

2. 

14  days 

61.65 

4.1 

33-i 

0.9 

12.90 

The  marked  uniformity  in  composition  notwithstanding  the  wide 
variation  in  the  fasting  periods  is  significant.  The  tensile  strength  of 
the  femur  of  the  dog  has  been  found  to  be  at  least  25,000  pounds  to  the 
square  inch1  whereas  that  of  oak  is  10,000  and  that  of  cast  iron  20,000 
pounds  to  the  square  inch. 

1  Johnston  and  Hawk:  Unpublished  data.     For  data  on  a  n  7-day  fast  by  dog  No.  i,  see 
Howe,  Mattill  and  Hawk:  Jour.  BioL  Chem.,  n,  103,  1912. 


EPITHELIAL  AND  CONNECTIVE  TISSUES  355 

EXPERIMENT  ON  OSSEOUS  TISSUE 

The  percentage  composition  of  normal  human  bone  and  of  bone  from 
a  case  of  osteomalacia  is  given  in  the  following  table  i1 


Constituent 

Kind  of  bone 

Normal 

Osteomalacia 

Calcium  (CaO)  

28.85 
0.14 

19-55 
0.14 

iS-44 
o.57 

12.01 

0.55 

Magnesium  (MgO) 

Phosphorus  (P2O6)  

Sulphur  (S)  

Qualitative  Analysis  of  Bone  Ash. — Take  i  gram  of  bone  ash  in  a  small 
beaker  and  add  a  little  dilute  nitric  acid.  What  does  the  effervescence  indicate? 
Stir  thoroughly  and  when  the  major  portion  of  the  ash  is  dissolved  add  an  equal 
volume  of  water  and  filter.  To  the  acid  filtrate  add-ammonium  hydroxide  to 
alkaline  reaction.  A  heavy  white  precipitate  of  phosphates  results.  (What 
phosphates  are  precipitated  here  by  the  ammonia?)  Filter  and  test  the  filtrate 
for  chlorides,  sulphates,  phosphates,  and  calcium.  Add  dilute  acetic  acid  to 
the  precipitate  on  the  paper  and  test  a  little  of  this  filtrate  for  calcium  and  phos- 
phates. Heat  the  remainder  of  the  filtrate  to  boiling  and  add  (NH4)2CO3  and 
NH4C1  slowly  to  this  hot  solution  as  long  as  a  precipitate  forms.  Filter  off  the 
precipitate  of  CaCo3  and  wash  with  hot  water  until  free  from  alkali.2  To  the 
filtrate  add  a  solution  of  Na2HPO4,  make  strongly  alkaline  with  NH4OH,  and 
note  the  formation  of  a  white  precipitate  of  ammonium  magnesium  phosphate 
(NH4MgPO4).  Examine  the  crystals  under  the  microscope  and  compare  with 
those  shown  hi  Fig.  134,  page  426.  To  the  precipitate  on  the  filter  paper,  which 
was  insoluble  in  acetic  acid  add  a  little  dilute  hydrochloric  acid  and  test  this 
last  filtrate  for  phosphates  and  iron. 

Reference  to  the  following  scheme  may  facilitate  the  analysis. 

1  McCrudden:  Jour.  Biol.  Chem.,  7,  199,  1910. 

2  Magnesium  is  not  precipitated  here  because  of  presence  of  NH4C1. 


356  PHYSIOLOGICAL  CHEMISTRY 

BONE  ASH. 

Add  dilute  nitric  acid,  stir  thoroughly  and  after  the  major  portion  of  the  ash  has  been 
brought  into  solution  add  a  little  distilled  water  and  filter. 


Residue  I.  Filtrate  I. 

(discard)  Add  ammonium  hydroxide  to 

alkaline  reaction  and  filter. 
I 


Residue 

Treat  on  paper  v 

H.                                         Filtrate  H. 
rith  acetic  acid.                       Test  for: 
i.  Chlorides. 

Residue  ffl. 

Treat  on  paper  with  hydro- 
chloric acid. 

Filtrate  IV. 

2.  Sulphates. 
Filtrate  m.                         3-  Phosphates. 
Test  for:                            *  Calcium, 
i.  Phosphates. 
2.  Calcium. 
3.  Magnesium 

Test  for: 

1.  Iron. 

2.  Phosphates. 


V.  ADIPOSE  TISSUE 


Adipose  tissue  consists  almost  entirely  of  a  mixture  of  fats.  For 
discussion  and  experiments  see  chapter  on  Fats,  page  179. 

VI.  TEETH 

TEETH  are  composed  of  enamel,  dentine  and  cement.  The  cement 
and  dentine  possess  practically  the  same  chemical  composition  as  bone. 
The  enamel  is  the  product  of  an  epithelial  tissue.  It  is  the  hardest 
substance  in  the  body  and  contains  the  smallest  amount  of  water 
(3-10  per  cent) l  According  to  Bertz2  the  enamel  and  dentine  of  human 
teeth  have  the  following  percentage  composition: 

Dentine  Enamel 

38.18  CaO  50.22 

1.51  MgO  0.73 

30.24  P2O5  40.69 

29.15  Organic  substance  6.82 

It  will  be  seen  that  calcium  phosphate  is  the  predominant  constituent 
of  each. 

In  dental  caries  there  may  be  a  pronounced  loss  of  inorganic  matter 
and  a  corresponding  gain  in  water  and  organic  substance.     These 
analyses  by  Klihns1  illustrate  this  change  in  percentage  composition 
Sound  Teeth  Dental  Caries 


4.27                                            H2O 

10.91 

52.90                                      Ca3(PO4)2 

14-47 

'12.93                                         CaC03 

7.92 

i.  08                                      Mg3(P04)2 

o-35 

28.39                               Organic  Substance 

66.38 

1  Aron:  Oppenheimer's  Handbuch,  Zweiter  band.  2.  teil,  page  208. 
2  Bertz:  Thesis,  Wiirzburg  1899,  p.  36. 
3Kiihns:  D.  Monatsschr.  Zahnheilk,  13,  361  and  450. 

CHAPTER   XX 
MUSCULAR  TISSUE 

THE  muscular  tissues  are  divided  physiologically  into  the  voluntary 
(striated)  and  the  involuntary  (non-striated  or  smooth).  In  the 
chemical  examination  of  muscular  tissue  the  voluntary  form  is  gener- 
ally employed.  Muscle  contains  about  25  per  cent  of  solid  matter, 
of  which  about  four-fifths  is  protein  material  and  the  remaining  one- 
fifth  extractives  and  inorganic  salts. 

The  proteins  are  the  most  important  of  the  constituents  of  muscular 
tissue.  In  the  living  muscle  we  find  two  proteins,  myosinogen  and 
para-myosinogen.  These  may  be  shown  to  be  present  in  muscle  plasma 
expressed  from  fresh  muscles.  In  common  with  the  plasma  of  the 
blood  this  muscle  plasma  has  the  power  of  coagulating,  and  the  clot 
formed  in  this  process  is  called  myosin.  According  to  Halliburton1 
and  others  in  the  onset  of  rigor  mortis  we  have  an  indication  of  the  for- 
mation of  this  myosin  clot  within  the  body.  The  relation  between  the 
proteins  of  living  and  dead  muscle  is  represented  graphically  by  Halli- 
burton as  follows: 

Proteins  of  the  living  muscle. 


I  I 

Para-myosinogen  (25%).  Myosinogen    (75%). 

Soluble  myosin. 


Myosin. 
(The  protein  of  the  muscle  clot.) 

Of  the  total  protein  content  of  living  muscle  about  75  per  cent  is 
made  up  by  the  myosinogen  and  the  remaining  25  per  cent  is  para- 
myosinogen.  These  proteins  may  be  separated  by  subjecting  the 
muscle  plasma  to  fractional  coagulation  in  the  usual  way.  Under 
these  conditions  the  para-myosinogen  is  found  to  coagulate  at  47°C. 
and  the  myosinogen  to  coagulate  at  56°C.  It  is  also  claimed  by  some 
investigators  that  it  is  possible  to  separate  these  two  proteins  by  the 
fractional  ammonium  sulphate  method,  but  the  possibility  of  making 

1  Halliburton:  Biochemistry  of  Muscle  and  Nerve,  1904,  p.  4. 

357 


PHYSIOLOGICAL  CHEMISTRY 

an  accurate  separation  by  this  method  is  somewhat  doubtful.  It  is 
well  established  that  para-myosinogen  is  a  globulin  since  it  responds  to 
certain  of  the  protein  precipitation  tests  and  is  insoluble  in  water. 
Myosinogen,  on  the  contrary,  is  not  a  typical  globulin  since  it  is 
soluble  in  water.  It  has  been  called  a  pseudo-globulin.  Myosin  pos- 
sesses the  globulin  characteristics.  It  is  insoluble  in  water  but  soluble 
in  the  other  protein  solvents  and  is  precipitated  from  its  solution  upon 
saturation  with  sodium  chloride. 

Our  ideas  concerning  the  cause  of  rigor  mortis  have  undergone  an  im- 
portant revision  in  recent  years.  A  very  attractive  theory  has  been 
advanced  by  Meigs1  and  experimental  confirmation  has  been  accorded 
it  by  von  Fiirth  and  Lenk.2  According  to  this  theory,  rigor  has  no 
connection  with  the  coagulation  of  the  muscle  proteins  and  may  even 
be  hindered  or  prevented  by  such  coagulation.  The  cause  of  rigor, 
from  this  new  viewpoint,  lies  in  the  imbibition  of  water  by  the  muscle 
colloids.  It  is  well  known  that  colloids  possess  the  property  of  absorb- 
ing whatever  fluid  may  be  in  contact  with  them.  Moreover,  the 
capacity  of  the  colloid  for  water  is  increased  if  the  fluid  is  slightly  acid 
in  reaction.  Therefore  the  postmortem  production  of  lactic  acid 
facilitates  the  imbibition  of  muscle  fluid  by  the  muscle  colloids. 
Under  such  conditions,  the  fibers  swell,  become  rigid  and  the  condition 
known  as  rigor  mortis  results.  The  disappearance  of  rigor  is  believed 
to  be  due  to  the  coagulation  of  the  muscle  protein  through  the  agency 
of  the  accumulated  lactic  acid.  This  change  is  accompanied  by  a  re- 
lease of  the  imbibed  water  by  the  colloids,  inasmuch  as  the  capacity 
of  a  colloid  for  retaining  fluid  is  lowered  by  coagulation. 

There  is  a  difference  of  opinion  as  to  whether  true  rigor  ever  occurs 
in  connection  with  non-striated  (smooth)3  muscle. 

Under  the  name  extractives  we  class  a  number  of  muscle  constituents 
which  occur  in  traces  in  the  tissue  and  may  be  extracted  by  water, 
alcohol,  or  ether.  There  are  two  classes  of  these  extractives,  the  non- 
nitrogenous  extractives  and  the  nitrogenous  extractives.  Grouped  under 
the  non-nitrogenous  bodies  we  have  glycogen,  dextrin,  sugars,  lactic 
acid,  inositol,  C6H6(OH)6,  and  fat.  In  the  class  of  nitrogenous  extract- 
ives we  have  creatine,  creatinine,  xanthine,  hypoxanthine,  uric  acid, 
urea,  carnine,  guanine,  phosphocarnic  acid,  inosinic  acid,  carnosine, 
taurine,  carnitine,  novaine,  ignotine,  neosine,  oblitine,  carnomuscarine, 
and  methylguanidine  (see  formulas  on  pp.  126  and  364).  Not  all  of 
these  extractives  are  present  in  the  muscles  of  all  species  of  animals. 

1  Meigs:  American  Journal  of  Physiology,  26,  191,  1910. 

2  von  Ftirth  and  Lenk:  Wiener  'klinische  Wochenschrift,  24,  1079,  1911. 

3  Saxl:  BeHrage  zur  chemischen  Physiologic  und  Pathologie,  9,  i,  1907. 


MUSCULAR   TISSUE  359 

Other  extractives  besides  those  enumerated  above  have  been  described 
and  there  are  undoubtedly  still  others  whose  presence  remains  undeter- 
mined. A  detailed  consideration  would,  however,  be  unprofitable  in 
this  place. 

Glycogen  is  an  important  constituent  of  muscle.  The  content 
of  this  polysaccharide  in  muscle  varies  and  is  markedly  decreased  by 
intense  muscular  activity.  It  is  transformed  into  sugar  and  used  as 
fuel.  The  liver  is  the  organ  which  stores  the  reserve  supply  of  glycogen 
and  transforms  it  into  glucose  which  is  passed  into  the  blood  stream 
and  so  carried  to  the  working  muscle  where  it  is  synthesized  into  gly- 
cogen. The  glycogen  thus  formed  is  then  changed  into  glucose  as  the 
working  muscle  may  need  it. 

Glycogen  is  a  polysaccharide  and  has  the  same  percentage  com- 
position as  starch  and  dextrin.  It  resembles  starch  in  forming  an  opal- 
escent solution  and  resembles  dextrin  in  being  very  soluble,  in  giving 
reddish  color  with  iodine  and  in  being  dextro-rotatory.  Glycogen  may 
be  prepared  from  muscle  by  extracting  with  boiling  water  and  then 
precipitating  the  glycogen  from  the  aqueous  solution  by  alcohol;  dilute 
or  concentrated  potassium  hydroxide  may  also  be  used  to  extract  the 
glycogen.  Glycogen  may  be  prepared  in  the  form  of  a  white,  tasteless, 
amorphous  powder.  It  is  completely  precipitated  from  its  solution 
by  saturation  with  solid  ammonium  sulphate,  but  is  not  precipitated  by 
saturation  with  sodium  chloride.  It  may  also  be  precipitated  by 
alcohol,  tannic  acid,  or  ammoniacal  basic  lead  acetate.  It  has  the 
power  of  holding  cupric  hydroxide  in  solution  in  alkaline  fluids  but 
cannot  reduce  it.  It  may  be  hydrolyzed  with  the  formation  of  glucose 
by  dilute  mineral  acids  and  is  readily  digested  by  amylolytic  enzymes. 

Mendel  and  Leavenworth  have  drawn  the  conclusion,  from  the  ex- 
amination of  embryo  pigs,  that  embryonic  structures  do  not  contain 
exceptionally  large  amounts  of  glycogen.  The  distribution  of  the 
glycogen  was  not  observed  to  differ  from  that  in  the  adult  animal  ex- 
cept that  the  liver  of  the  embryo  does  not  assume  its  glycogen-stor- 
ing  function  early.  They  further  draw  the  conclusion  that  the  meta- 
bolic transformations  of  glycogen  in  the  embryo  and  the  adult  are 
entirely  analogous. 

The  lactic  acid  occurring  in  the  muscular  tissue  of  vertebrates  is 
paralactic  or  sarcolactic  acid,1 

H     OH 

I       I 
H—  C—  C—  COOH. 

I       I 
H     H 

is  dextro-rotatory,  whereas  fermentation  lactic  acid  (<f-Mactic  acid)  is  optically 


inactive. 


360  PHYSIOLOGICAL  CHEMISTRY 

The  reaction  of  an  inactive  living  muscle  is  alkaline,  but  upon  the  death 
of  the  muscle,  or  after  the  continued  activity  of  a  living  muscle,  the 
reaction  becomes  acid,  due  to  the  formation  of  lactic  acid.  There  is  a 
difference  of  opinion  regarding  the  origin  of  this  lactic  acid.  Some 
investigators  claim  it  to  arise  from  the  carbohydrates  of  the  muscle, 
while  others  ascribe  to  it  a  protein  origin.  The  strongest  evidence 
favors  a  carbohydrate  source.1 


FIG.  115. — CREATINE. 

Among  the  nitrogenous  extractives  of  muscle,  those  which  are  of  the 
most  interest  in  this  connection  are  creatine  and  the  purine  bases, 
xanthine  and  hypoxanthine.  Creatine  is  found  in  varying  amounts  in 
the  muscles  of  different  species,  the  muscles  of  birds  having  shown 
the  largest  amount.  It  has  also  been  found  in  the  blood,  the  brain,  in 
transudates  and  in  the  thyroid  gland.  Creatine  may  be  crystallized 
and  forms  colorless  rhombic  prisms  (Fig.  115)  which  are  soluble  in 
warm  water  and  practically  insoluble  in  alcohol  and  ether.  Upon 
boiling  a  solution  of  creatine  with  dilute  hydrochloric  acid  it  is  dehydro- 
lyzed  and  its  anhydride  creatinine  is  formed.  The  theory  that  the 
creatine  of  ingested  meat  is  transformed  into  creatinine  and  excreted 
in  the  urine  has  been  proven  untenable  through  the  researches  of  Folin, 
Klercker,  and  Wolf  and  Shaffer.  It  is  now  known  that  under  normal 
conditions  the  ingestion  of  creatine  in  no  way  influences  the  excretion 
of  creatinine.  In  the  case  of  Eck  fistula  dogs,  however,  London  and 
Bolyarski2  found  ingested  creatine  to  increase  the  output  of  creatinine 
in  the  urine.  This  finding  is  of  importance  as  throwing  light  upon  the 

lLevene  and  Meyer:  Jour.  BioL  Chem.,  n,  361,  1912. 
•London  and  Bolyarski:  Zeit.  phys.  chem.,  62,  465,  1909. 


MUSCULAR  TISSUE  361 

r61e  of  the  liver  in  creatine  and  creatinine  metabolism.  In  this  con- 
nection it  is  important  to  note  that  there  is  no  normal  excretion  of 
endogenous  (see  page  395)  creatine,  a  statement  proven  by  the  fact  that 
if  no  creatine  be  ingested  none  will  be  excreted.  Folin1  has  shown  that 
the  main  bulk  of  ingested  creatine  is  retained  in  the  body,  unless  the  diet 
contains  a  large  amount  of  protein  material.  In  fasting  the  urine 
contains  considerable  creatine,  i.e.,  120  mg.  or  more  per  day.  Under 
certain  pathological  conditions,  e.g.,  fevers,  the  urine  may  contain 
endogenous  creatine  which  is  probably  derived  from  the  catabolism 
of  muscular  tissue,  as  Benedict,  Mellanby,  and  Shaffer  have  suggested. 
Benedict  and  Osterberg2  believe  we  may  have  a  high  creatine  elimina- 
tion which  has  no  relation  to  the  catabolism  of  muscle. 

McCrudden3  reports  creatine  in  the  urine  in  cases  of  infantilism, 
achondroplasia  and  cretinism  the  amount  present  being  increased 
when  the  carbohydrate  ingestion  was  increased. 

It  has  been  stated  that  creatine  does  not  occur  in  non-striated 
muscle.  It  has,  however,  been  found  in  the  ribn-striated  muscles  of 
the  lamprey  the  lowest  form  of  vertebrates.4 

Amberg  and  Morrill,5  Sedgwick,6  Rose7  and  Folin8  have  shown  that 
creatine  is  a  normal  constituent  of  the  urine  of  infants  and  children 
(10-15  mg-  Per  day).  Folin  explains  this  phenomenon  on  the  basis  of 
the  relatively  high  protein  intake,  whereas  Rose  believes  it  is  due  to  a 
peculiar  carbohydrate  metabolism. 

Besides  being  a  normal  constituent  of  muscle,  xan thine  has  been 
found  in  the  brain,  spleen,  pancreas,  thy'mus,  kidneys,  testicles,  liver, 
and  in  the  urine.  It  may  be  obtained  in  crystalline  form  (Fig.  116, 
p.  362),  but  ordinarily  it  is  amorphous.  Xanthine  is  easily  soluble  in 
alkalis,  less  soluble  in  water  and  dilute  acids,  and  entirely  insoluble  in 
alcohol  and  ether. 

Hypoxanthine  occurs  ordinarily  in  those  tissues  and  fluids  which 
contain  xanthine.  It  has  been  found,  unaccompanied  by  xanthine,  in 
bone  marVow  and  in  milk.  Unlike  xanthine  it  may  be  easily  crystallized 
in  the  form  of  small,  colorless  needles.  It  is  readily  soluble  in  alkalis, 
acids,  and  boiling  water,  less  soluble  in  cold  water  and  practically  in- 
soluble in  alcohol  and  ether. 
^  The  predominating  inorganic  salt  of  muscle  is  potassium  phosphate 

1  Folin:  Hammarsten  Festschrift,  p.  15. 

2  Benedict  and  Osterberg:  Jour.  Biol.  Chem.,  18,  195,  1914. 

3  Me  Crudden:  Jour.  Expt.  Med.,  15,  457,  1912. 

4  Mellanby:  Jour,  of  PhysioL,  36,  472,  1908.     Wilson:  Jour.  Biol.  Chem.,  18,  17,  1914. 
6  Amberg  and  Morrill:  Jour.  Biol.  Chem.,  3,  311,  1907. 

6  Sedgwick:  Jour.  Am.  Med.  Ass'n,  55,  1178,  1910. 

7  Rose:  Jour.  Biol.  Chem.,  10,  265,  1911. 

8  Folin:  Ibid.,  n,  253,  1912. 


362 


PHYSIOLOGICAL   CHEMISTRY 


Besides  this  salt  we  have  present  chlorides  and  salts  of  sodium,  calcium, 
magnesium,  and  iron.     Sulphates  are  present  in  traces. 

Mendel  and  Saiki  have  made  some  interesting  observations  upon  the 
chemical  composition  of  non-striated  or  smooth  (involuntary)  mammalian 
muscle,  such  as  the  urinary  bladder  and  the  muscular  coat  of  the  stom- 
ach of  the  pig.  Hypoxanthine  was  found  to  be  the  predominant  purine 
base  present.  Creatine  and  paralactic  acid  were  also  isolated.  These 
investigators  were  unable  to  demonstrate,  definitely,  the  presence  of 
glycogen  in  the  non-striated  muscles  studied,  but  state  that  "the 
tissues  possess  the  property  of  transforming  glycogen  in  the  char- 


FIG.  116. — XANTHINE. 
After  the  drawings  of  Horbaczewski,  as  represented  in  Neubauer  and  Vogel. 


(Ogden.) 


acteristic  enzymatic  way."  The  most  important  part  of  their  in- 
vestigation consists  in  a  rather  complete  analysis  of  the  inorganic 
constituents  of  these  muscles.  A  notable  difference  in  the  relative 
distribution  of  the  various  inorganic  constituents  was  observed,  a 
difference  which,  according  to  the  authors,  "can  be  accounted  for  in 
part  only  by  an  admixture  of  lymph."  The  comparative  composition 
of  the  inorganic  portion  of  striated  and  non-striated  muscle  and  of  blood 
serum  for  comparison  is  shown  in  the  following  table: 


Per  100  parts  of  fresh  muscle 

K20 

Na20 

Fe208 

CaO 

MgO 

Cl 

P206 

H20 

Non-striated  muscle  (Mendel  and  Saiki) 
Skeletal  muscle  (Katz) 

0.081 
0.306 
0.027 

0.328 

0.210 
0.425 

O.OII 

0.008 

0.044 

O.OII 
0.012 

0.007 
0.047 
0.004 

0.171 
0.048 
0.363 

0.184 
0.487 

0.020 

80.6 
72.9 
91.8 

Blood  serum  (Abderhalden)  

An  interesting  comparative  study  of  the  ash  of  the  smooth  muscle  of 


MUSCULAR   TISSUE 


363 


the  stomach  of  the  frog  and  the  striated  muscle  from  the  same  animal 
was  very  recently  reported  by  Meigs  and  Ryan.1  Their  data  indicate 
"that  smooth  muscle  contains  somewhat  less  potassium  and  phos- 
phorus and  somewhat  more  sodium  and  chlorine  than  the  striated 
muscle  of  the  same  animal,  but  that  the  differences  in  these  respects 
between  the  two  tissues  are  not  by  any  means  so  marked  as  has  some- 
times been  supposed."  Their  average  figures  for  each  type  of  muscle 
follow : 


Muscle 

Per  100  parts  of  fresh  muscle 

K 

Na 

Fe 

Ca 

Mg 

P 

Cl 

s 

Solids 

HaO 

Striated 

0.350 
0.325 

0.054 
0.073 

. 

O.OIO 

o  .  0007 

0.028 
0.004 

0.030 
0.013 

0.155 
0.137 

0.066 

0.120 

0.141 
o.  161 

20.13 
17.70 

79-87 
82.30 

Smooth                

The  preparation  from  which  the  above  data  for  smooth  muscle 
were  obtained  were  shown  by  histological  examination  to  consist  in 
large  part  of  smooth  muscle  fibers. 

Muscular  tissue  is  said  to  contain  a  reddish  pigment  called  myo- 
hematin,  which  is  a  derivative  of  hemoglobin. 

The  so-called  "fatigue  substances"  of  muscle  are  carbon  dioxide, 
paralactic  acid,  and  potassium  dihydrogen  phosphate. 

The  ordinary  commercial  "meat  extract"  is  composed  principally 
of  the  water-soluble  constituents  of  muscle  and  contains  practically 
nothing  of  nutritive  value.  The  protein  material  to  which  meat  owes 
its  value  as  an  article  of  diet  is  ordinarily  practically  all  removed  in 
the  preparation  of  the  extract.  Occasionally  some  preparations  are 
found  to  contain  proteose,  which  is  formed  from  the  meat  proteins  in 
the  process  of  preparation. 

Lusk2  has  shown  that  Liebig's  extract  is  without  influence  upon  the 
metabolism  (energy)  in  spite  of  the  glandular  activity  it  is  known  to 
induce. 

The  structural  formulas  of  some  of  the  nitrogenous  extractives  of 
muscle  are  as  follows: 


NH2 
HN=C 


HN 

I 
HN=C 


CO 

i 


N(CH3).CH2.COOH. 

CREATINE,  CiHtNsOj. 

M ethyl-guanidine  acetic  acid. 

1  Meigs  and  Ryan:  Journal  of  Biological  Chemistry,  n,  401,  1912 
'Lusk:  Jour.  Biol.  Chem.,  13,  155,  1912. 


N(CH3).CH2 

CREATININE,  CiHT 
Creatine  anhydride. 


364 


PHYSIOLOGICAL   CHEMISTRY 


NH2 
C  =  0 
NH2 

UREA,  CONjH4 


CH2.NH2 
CH2.S02OH 


o 


TAURINE,  CaHrNSOj. 
Amino-ethyl  sulphonic  acid. 

CO 


(CH3)3.N 

CH2— CH.OH— CH2 

CARNITINE,  CvHisNOj. 
y-trimethyloxybutyrobetaine. 

OH 
(CH3)3N 

CH2.CH2.CH2.CH(OH)2 

NOVAINE,  CTHnNOj. 

Tri-methyl  di-hydroxybutyl  ammonium  hydroxide. 


Carnosine, 

Neosine,  C6H17NO2. 

Ignotine,  C9Hi4N4O3. 

Phosphocarnic  acid,  Ci0Hi7N3O5  or  CioHi5N3O5. 

Inosinic  acid,  (HO)2.PO.O.CH2(CHOH)3.CH:(C5H3N40). 

Purine  Bodies.1 — 

HN— CO  HN— CO 


HC     C— NH 


OC     C— NH 


CH 


N— C— N 

HYPOXANTHINE,  C&HiNiO. 
6-oxypurine. 

HN— CO 


H2N.C      C— NH 

\CH 

N— C— N 

GUANINE,  CcHiNiO. 
2-amino-6-oxypurine. 


CH 


HN—  C—  N 

XANTHINE, 
2-6-dioxypurine. 


=  C.NH2 


HC     C— NH 

i    > 

.  N— C— N 

ADENINE,  CsHsNj. 
6-aminopurine. 


i  *.*. 

>CH 


EXPERIMENTS  ON  MUSCULAR  TISSUE 

I.  Experiments  on  "Living"  Muscle 

i.  Preparation  of  Muscle  Plasma  (Halliburton). — Wash  out  the  blood  vessels 
of  a  freshly  killed  rabbit  with  0.9  per  cent  sodium  chloride.    This  can  best  be 

1  For  discussion  of  the  purine  bodies  which  are  found  as  muscle  extractive  see  Chapter 
VI  on  Nucleic  Acids. 


MUSCULAR  TISSUE  365 

done  by  opening  the  abdomen  and  inserting  a  cannula  into  the  aorta.  Now 
remove  the  skin  from  the  lower  limbs,  cut  away  the  muscles  and  divide  them 
into  very  small  pieces  by  means  of  a  meat  chopper.  Transfer  the  pieces  of 
muscle  to  a  mortar  and  grind  them  with  clean  sand  and  a  little  ice  cold  5  per 
cent  magnesium  sulphate.  Place  in  an  ice-box  over  night.  Filter  off  the  salted 
muscle  plasma  and  make  the  following  tests : 

(a)  Reaction. — Test  the  reaction  to  litmus,  phenolphthalein,  and  Congo  red. 
What  is  the  reaction  of  this  fresh  muscle  plasma? 

(b)  Fractional  Coagulation. — Place  a  little  muscle  plasma  in  a  test-tube  and 
arrange  the  apparatus  for  fractional  coagulation  as  explained  on  page  104.    Raise 
the  temperature  very  carefully  from  3O°C.  and  note  any  changes  which  may  occur 
and  the  exact  temperature  at  which  such  changes  take  place.    When  the  first 
protein  (para-myosinogen)  coagulates  filter  it  off  and  then  heat  the  clear  filtrate 
as  before,  being  careful  to  note  the  exact  temperature  at  which  the  next  coagula- 
tion (myosinogen)  occurs.    There  will  probably  be  a  preliminary  opalescence  in 
each  case  before  the  real  coagulation  occurs.    Therefore  do  not  mistake  the 
real  coagulation-point  and  filter  ^t  the  wrong  time.    What  are  the  coagulation 
temperatures  of  these  two  proteins?    Which  protein  was  present  in  greater 
amount? 

(c)  Formation  of  the  Myosin  Clot. — Dilute  a  portion  of  the  plasma  with  3 
or  4  times  its  volume  of  water  and  place  it  on  a  water-bath  or  in  an  incubator 
at  35°C.  for  several  hours.    A  typical  myosin  clot  should  form.    Note  the  muscle 
serum  surrounding  the  clot.    Now  test  the  reaction.    Has  the  reaction  changed, 
and  if  so  to  what  is  the  change  due?    Make  a  test  for  lactic  acid.    What  do  you 
conclude? 

2.  Preparation  of  Muscle  Plasma  (v.  Furth). — Remove  the  blood-free  muscles 
of  a  rabbit  as  explained  above.     Finely  divide  by  means  of  a  meat  chopper  and 
grind  in  a  mortar  with  a  little  clean  sand  and  some  0.9  per  cent,  sodium  chloride. 
Wrap  portions  of  the  muscle  in  muslin  and  press  thoroughly  by  means  of  a  tincture 
press  or  lemon  squeezer.     Filter  and  make  the  tests  according  to  the  directions 
given  in  the  last  experiment. 

3.  "Fuchsin-frog"  Experiment. — Inject  a  saturated  aqueous   solution  of 
Fuchsin  "  S  "  into  the  lymph  spaces  of  a  frog  two  or  three  times  daily  for  one  or 
two  days,  in  this  way  thoroughly  saturating  the  tissues  with  the  dye.    Pith  the 
animal  (insert  a  heavy  wire  or  blunt  needle  through  the  occipito  atlantoid  mem- 
brane), remove  the  skin  from  both  hind  legs  and  expose  the  sciatic  nerve  in  one  of 
them.   Insert  a  small  wire  hook  through  the  jaws  of  the  frog  and  suspend  the  ani- 
mal from  an  ordinary  clamp  or  iron  ring.    Pass  electrodes  under  the  exposed 
sciatic  nerve,  and  after  tying  the  other  leg  to  prevent  any  muscular  movement, 
stimulate  the  exposed  nerve  by  means  of  make  and  break  shocks  from  an  in- 
duction coil.    The  stimulated  leg  responds  by  pronounced  muscular  contrac- 
tions, whereas  the  tied  leg  remains  inactive.    Continue  the  stimulation  until 
the  muscles  are  fatigued.    The  muscular  activity  has  caused  the  production  of 
lactic  acid  and  this  hi  turn  has  reacted  with  the  injected  fuchsin  to  cause  a  pink 
or  red  color  to  develop.    The  muscles  of  the  inactive  leg  still  remain  unchanged 
in  color. 

The  normal  color  of  the  Fuchsin  "  S  "  when  injected  was  red,  but  upon  being 
absorbed  it  became  colorless  through  the  action  of  the  alkalinity  of  the  blood. 
Upon  stimulating  the  muscles,  however,  as  above  explained,  lactic  acid  was 


366  PHYSIOLOGICAL  CHEMISTRY 

formed  and  this  acid  reacted  with  the  fuchsin  and  again  produced  the  original 
color  of  the  dye. 

11.  Experiments  on  "Dead"  Muscle 

1.  Preparation  of  Myosin. — Take  25  grams  of  finely  divided  lean  beef  which 
has  been  carefully  washed  to  remove  blood  and  lymph  constituents  and  place 
it  in  a  beaker  with  10  per  cent  sodium  chloride.     Stir  occasionally  for  several 
hours.    Strain  off  the  meat  pieces  by  means  of  cheese  cloth,  filter  the  solution 
and  saturate  it  with  sodium  chloride  hi  substance.    Filter  off  the  precipitate  of 
myosin  and  make  the  tests  as  given  below.    This  filtration  will  proceed  very 
slowly.    Myosin  collects  as  a  film  on  the  sides  of  the  filter  paper  and  may  be 
removed  and  tested  before  the  entire  volume  of  fluid  has  been  filtered.    If  this 
precipitate  remains  for  any  length  of  time  on  the  paper  in  contact  with  the  air 
it  will  become  transformed  into  the  protean  myosan.    Test  the  myosin  precipi- 
tate as  follows : 

(a)  Solubility. — Try  its  solubility  in  water  sodium  chloride,  dilute  acid  and 
alkali.    Is  myosin  an  albumin  or  a  globulin? 

(b)  Xanthoproteic  Reaction. — See  page  98. 

(c)  Coagulation  Test. — Suspend  a  little  of  the  myosin  in  water  in  a  test- 
tube  and  heat  to  boiling  for  a  few  minutes.    Now  remove  the  suspended  ma- 
terial and  try  its  solubility  in  10  per  cent  sodium  chloride.    What  property  does 
this  experiment  show  myosin  to  possess? 

Test  the  filtrate  from  the  original  myosin  precipitate  as  follows : 

(a)  Biuret  Test.— What  does  this  show? 

(b)  Place  a  little  of  the  solution  in  a  test-tube  and  heat  to  boiling.    At  the 
boiling-point  add  a  drop  of  dilute  acetic  acid  and  filter.    Test  this  filtrate  for 
proteose  with  picric  acid.    Is  any  proteose  present?    Saturate  another  portion 
of  the  filtrate  with  ammonium  sulphate  and  test  for  peptone  in  the  usual  way 
(see  page  119).    Do  you  find  any  peptone? 

From  your  experiments  on  "living"  and  "dead"  muscle  what  are 
your  ideas  regarding  the  proteins  of  muscle? 

2.  Preparation  of  Glycogen. — Grind  a  few  oysters  or  scallops1  in  a  mortar 
with  sand.    Transfer  to  an  evaporating  dish,  add  water,  and  boil  for  20  minutes. 
Note  the  opalescence  of  the  solution.    At  the  boiling-point  faintly  acidify  with 
acetic  acid.    Why  is  this  acid  added?    Filter,  and  divide  the  filtrate  into  two 
parts.    Test  one  part  of  the  filtrate  as  follows : 

(a)  Iodine  Test. — To  5  c.c.  of  the  solution  in  a  test-tube  add  5-10  drops  of 
iodine  solution  and  2-3  drops  of  10  per  cent  sodium  chloride.  What  do  you 
observe?  Is  this  similar  to  the  iodine  test  upon  any  other  body  with  which  we 
have  had  to  deal? 

If  difficulty  is  experienced  in  securing  a  satisfactory  iodine  test  proceed  as 
follows :  Make  equal  volumes  of  glycogen  solution  acid  in  reaction  with  hydro- 
chloric acid..  Boil  one  solution  to  hydrolyze  the  glycogen.  Add  equal  volumes 

1  Glycogen  may  also  be  prepared  from  the  liver  of  an  animal  which  has  been  fed  a  high 
carbohydrate  diet  for  1-2  days  previously.  The  best  yield  of  glycogen  can,  however,  gen- 
erally be  obtained  from  scallops.  To  secure  best  yield  of  glycogen  the  liver,  scallops  or 
oysters  should  be  fresh.  Canned  oysters  or  scallops  may  be  used  if  fresh  ones  are  not 
available.  If  permitted  to  stand  some  glycogen  will  be  converted  into  glucose. 


MUSCULAR   TISSUE  367 

of  iodine  solution  to  each  and  note  the  more  pronounced   iodine    reaction 
in  the  unhydrolyzed  solution. 

(b)  Reduction  Test. — Does  the  solution  reduce  Fehling's  solution? 

(c)  Hydrolysis  of  Glycogen. — Add  10  drops  of  concentrated  hydrochloric  acid 
to  10  c.c.  of  the  solution  and  boil  for  10  minutes.    Cool  the  solution,  neutralize 
with  solid  potassium  hydroxide  and  test  with  Fehling's  solution.    Does  it  still 
fail  to  reduce  Fehling's  solution?    If  you  find  a  reduction  how  can  you  prove  the 
identity  of  the  reducing  substance? 

(d)  Influence  of  Saliva. — Place  5  c.c.  of  the  solution  hi  a  test-tube,  add  5 
drops  of  saliva  and  place  on  the  bath-water  at  4O°C.  for  10  minutes.    Does  this 
now  reduce  Fehling's  solution? 

To  the  second  part  of  the  glycogen  filtrate  add  3-4  volumes  of  95  per  cent 
alcohol.  Allow  the  glycogen  precipitate  to  settle,  decant  the  supernatant  fluid, 
and  filter  the  remainder.  Heat  the  glycogen  on  a  water-bath  to  remove  the 
alcohol,  then  subject  it  to  the  following  tests : 

(a)  Solubility. — Try  its  solubility  in  water  and  10  per  cent  sodium  chloride 
solution. 

(b)  Iodine  Test. — Place  a  small  amount  of  the  glycogen  in  a  depression  of  a 
test-tablet  and  add  2-3  drops  of  dilute  iodine  solution  and  a  trace  of  a  sodium 
chloride  solution.    The  same  wine-red  color  is  observed  as  in  the  iodine  test 
upon  the  glycogen  solution. 

3.  Testing  for  Inorganic  Constituents. — (a)  Examination  of  Ash  of  Muscle. — 
Incinerate  a  small  amount  of  muscular  tissue,  dissolve  the  ash  in  dilute  hydro- 
chloric acid.  Test  for  potassium,  phosphates,  magnesium,  calcium  and  chlorides. 

(b)  Demonstration  of  Phosphates  and  Magnesium  in  Muscle  (Hiirthle's 
Experiment). — Tease  a  very  small  piece  of  frog's  muscle  on  a  microscopical 
slide.  Expose  the  slide  to  ammonia  vapor  for  a  few  moments,  then  adjust  a 
cover-glass,  and  examine  the  muscle  fibers  under  the  microscope.  Note  the 
large  number  of  crystals  of  ammonium  magnesium  phosphate,  distributed  every- 

NH4-O 

\ 
Mg-0-P=O 

\/ 
0 

where  throughout  the  muscle  fiber,  thus  demonstrating  the  abundance  of  phos- 
phates and  magnesium  hi  the  muscle  (Fig.  134,  page  426). 

Separation  of  Extractives  from  Muscles 

i.  Creatine. — Dissolve  about  10  grams  of  a  commercial  extract  of  meat  hi 
200  c.c.  of  warm  water.  (Test  for  Protein  by  Biuret  and  Coagulation  Tests,  see 
Chapter  V.)  Precipitate  the  inorganic  constituents  by  neutral  lead  acetate, 
being  careful  not  to  add  an  excess  of  the  reagent.  Write  the  equations  for  the 
reactions  taking  place  here.  Allow  the  precipitate  to  settle,  then  filter  and  remove 
the  excess  of  lead  in  the  warm  filtrate  by  hydrogen  sulphide.  Filter  while  the  solu- 
tion is  yet  warm,  evaporate  the  clear  filtrate  to  a  syrup,  and  allow  it  to  stand  at 
least  48  hours  in  a  cool  place.  Crystals  of  creatine  should  form  at  this  point. 
Examine  under  the  microscope  (Fig.  115,  page  360).  Treat  the  syrup  with  200 


368  PHYSIOLOGICAL  CHEMISTRY 

c.c.  of  88  per  cent  alcohol,  stir  well  with  a  glass  rod  to  bring  all  soluble  material 
into  solution,  and  then  filter.  The  purine  bases  have  been  dissolved  and  are  in 
the  filtrate,  whereas  the  creatine  crystals  were  insoluble  hi  the  88  per  cent  alcohol 
and, remain  on  the  filter  paper.  Wash  the  crystals  with  88  per  cent  alcohol, 
then  remove  them  and  bring  them  into  solution  in  a  little  hot  water.  Decolorize 
the  solution  by  annual  charcoal  and  concentrate  it  to  a  small  volume.  Allow 
the  solution  to  cool  and  note  the  separation  of  colorless  crystals  of  creatine.1 
Make  the  following  tests  on  the  crystals : 

(a)  Microscopical  Examination. — Examine  some  crystals  under  the  micro- 
scope and  compare  the  form  with  those  reproduced  in  Fig.  115,  page  360. 

(b)  Transformation  of  Creatine  into  Creatinine. — Dissolve  the  crystals  in 
about  30  c.c.  of  hot  water.    To  one-half  of  the  solution  in  a  flask  add  an  equal 
volume  of  normal  hydrochloric  acid  and  heat  on  a  boiling  water-bath  for  five 
hours  with  reflux  condenser.    The  creatine  has  been  changed  into  creatinine. 
Apply  tests  for  creatinine  as  given  hi  Chapter  XXIII  to  the  original  solution  as 
well  as  to  the  acidified  solution. 

Diacetyl  Reaction. — To  5  c.c.  of  a  dilute  creatine  solution  add  an  equal  vol- 
ume of  saturated  sodium  carbonate  solution  and  a  few  drops  of  a  solution  of 
diacetyl.  A  pink  color  should  develop.  This  test  has  been  made  the  basis  of  a 
method  for  the  quantitative  determination  of  creatine.2 

2.  Hypoxanthine. — Evaporate  the  alcoholic  filtrate  from  the  creatine  to  re- 
move the  alcohol.    Make  the  solution  ammoniacal  and  add  ammoniacal  silver 
nitrate  until  precipitation  ceases.    The  precipitate  consists  principally  of  hypo- 
xanthine  silver  and  xanthine  silver.    Collect  these  silver  salts  on  a  filter  paper 
and  wash  them  with  water.    Place  the  precipitate  and  paper  in  an  evaporating 
dish  and  boil  for  one  minute  with  nitric  acid  having  a  specific  gravity  of  i.i. 
Filter  while  hot  through  a  double  paper,  wash  with  the  same  strength  of  nitric 
acid  and  allow  the  solution  to  cool.    By  this  treatment  with  nitric  acid  hypo- 
xanthine  silver  nitrate  and  xanthine  silver  nitrate  have  been  formed.     The 
former  is  insoluble  hi  the  cold  solution  and  separates  on  standing.    After  stand- 
ing several  hours  filter  off  the  hypoxanthine  silver  nitrate  and  wash  with  water  until 
the  wash  water  is  only  slightly  acid  in  reaction.    Examine  the  crystals  of  hypo- 
xanthine silver  nitrate  under  the  microscope  and  compare  them  with  those  hi 
Fig.  117.    Now  wash  the  crystals  from  the  paper  into  a  beaker  with  a  little 
water  and  warm  the  liquid.    Remove  the  silver  by  hydrogen  sulphide  and  filter. 
By  this  means  hypoxanthine  nitrate  has  been  formed  and  is  present  in  the  filtrate. 
(For  crystalline  form  of  hypoxanthine  nitrate  see  Fig.  40,  p.  135.)     Concentrate 
on  a  water-bath  to  drive  off  hydrogen  sulphide,  and  render  the  solution  slightly 
alkaline  with  ammonia.    Warm  for  a  time,  to  remove  the  free  ammonia,  filter, 
concentrate  the  filtrate  to  a  small  volume  and  allow  it  to  stand  in  a  cool  place. 
Hypoxanthine   should   crystallize   hi   small   colorless  needles.    Examine    the 
crystals  under  the  microscope. 

3.  Xanthine. — To  the  filtrate  from  the  above  experiment  containing  the  xan- 
thine silver  nitrate  add  ammonia  hi  excess.     (The  crystalline  form  of  xan- 
thine silver  nitrate  is  shown  in  Fig.   118.)    A  brownish-red  precipitate  of 
xanthine  silver  forms.    Filter  off  precipitate,  suspend  in  water  and  treat  with 

1  For  an  improved  method  of  preparing  pure  creatine  from  creatinine  see  chapter  on 
Physiological  Constituents  of  the  Urine. 
*  Walpole:  Jour.  PhysioL,  42,  301,  1911. 


MUSCULAR   TISSUE 


369 


hydrogen  sulphide  (do  not  use  an  excess  of  hydrogen  sulphide)  then  warm 
the  mixture  for  a  few  moments  and  filter  while  hot.     Concentrate  the  filtrate 


FIG.  117. — HYPOXANTHINE  SILVER  NITRATE. 
(Drawn  from  a  student  preparation  by  Dr.  E.  F.  Hirsch.) 

to  a  small  volume  and  put  away  in  a  cool  place  for  crystallization  (Fig.  116, 
page  362).    To  obtain  xanthine  in  crystalline  form  special  precautions  are 


FIG.  1 1 8. — XANTHINE  SILVER  NITRATE. 

generally  necessary.    Evaporate  the  solution  to  dryness  and  test  according  to 
directions  given  in  Chapter  VI  on  Nucleic  Acids. 


CHAPTER  XXI 
NERVOUS  TISSUE 

IN  common  with  the  other  solid  tissues  of  the  body,  nervous  tissue 
contains  a  large  amount  of  water.  The  percentage  of  water  present 
depends  upon  the  particular  form  of  nervous  tissue  but  in  all  forms  it  is 
invariably  greater  in  the  gray  matter  than  in  the  white.  Embryonic 
nervous  tissues  also  contain  a  larger  percentage  of  water  than  the  tissues 
of  adult  life.  The  gray  matter  of  the  brain  of  the  foetus,  for  instance, 
contains  about  92  per  cent  of  water,  whereas  the  gray  matter  of  the 
brain  of  the  adult  contains  but  83-84  per  cent  of  the  fluid. 

Among  the  solid  constituents  of  nervous  tissue  are  proteins,  choles- 
terol, cerebrosides  (cerebrin,  etc.),  lecithin,  kephalin,  protagon  (?),  para- 
nucleoprotagon,  nuclein,  neurokeratin,  collagen,  extractives,  and  inorganic 
salts.  The  proteins  are  present  in  the  greatest  amount  and  comprise 
about  50  per  cent  of  the  total  solids.  Three  distinct  proteins,  two 
globulins,  and  a  nucleoprotein,  have  been  isolated  from  the  nervous 
tissue.  The  globulins  coagulate  at  47°C.  and  70-7 5°C.,  respectively, 
while  the  nucleoprotein  coagulates  at  56-6o°C.  This  nucleoprotein 
contains  about  0.5  per  cent  of  phosphorus  (Halliburton,  Levene). 
Nervous  tissue  is  composed  of  a  relatively  large  quantity  of  a  variety 
of  compounds  which  collectively  may  be  grouped  under  the  term 
"lipoid" — substances  resembling  the  fats  in  some  of  their  physical 
properties  and  reactions  but  distinct  in  their  composition.  We  will 
class  cholesterol,  the  cerebrosides  and  the  phosphorized  fats  as  lipoids. 

The  consideration  of  lipoids  (or  lipins1}  is  assuming  added  impor- 
tance. These  substances  constitute  one  of  the  two  great  groups  of 
tissue  colloids,  the  proteins  being  the  remaining  group.  So  far  as  struc- 
ture and  chemical  properties  are  concerned  the  various  classes  of  lipoids 
are  entirely  unlike. 

The  group  of  phosphorized  fats  are  very  important  constituents  of 
nervous  tissue.  The  best  known  members  of  this  group  are  lecithin 
protagon  (?)  and  kephalin.  Lecithin  occurs  in  larger  amount  than 
the  other  members  of  the  group,  has  been  more  thoroughly  studied 
than  the  .others  and  is  apparently  of  greater  importance.  Upon  de- 
composition lecithin  yields  fatty  acids,  glycero-phosphoric  acid,  and 

1  Rosenbloom  and  Gies:  Biochemical  Bulletin,  i,  51,  1911.     The  term  lipoid  was  intro- 
duced by  Overton  (Studien  iiber  die  Narkose,  Jena,  1901,  Gustav  Fischer). 

370 


NERVOUS   TISSUE  371 

choline.  Each  lecithin  molecule  contains  two  fatty  acid  radicals 
which  may  be  those  of  the  same  or  different  fatty  acids.  Thus  we  have 
different  lecithins  depending  upon  the  particular  fatty  acids  radicals 
which  are  present  in  the  molecule.  The  formula  of  a  typical  lecithin 
would  be  the  following. 

CH2— OOC.C17H35 
CH— OOC.Ci7H35 
CH20— PO— O.C2H4 


OH  HO 

This  lecithin  would  be  called  distearyl-lecithin  or  cholyl-distearyl- 
glycero-phosphoric  acid.  Upon  decomposition  the  molecule  splits  ac- 
cording to  the  following  reaction: 

C44H9oNPO9  +  3H20  -*  2Ci8H3602  +  C3H9P06  +  C5H15N02. 

Lecithin.  Stearic  acid.        Glycero-phosphoric  acid.        Choline. 

The  lecithins  are  not  confined  to  the  nervous  tissues  but  are  found  in 
nearly  all  animal  and  Vegetable  tissues.  Lecithin  is  a  primary  con- 
stituent of  the  cell.  It  is  soluble  in  chloroform,  ether,  alcohol,  benzene, 
and  carbon  disulphide.  The  chloroform  or  alcohol-ether  solution 
may  be  precipitated  by  acetone.  Lecithin  may  be  caused  to  crystal- 
lize in  the  form  of  small  plates  by  cooling  the  alcoholic  solution  to  a 
low  temperature.  It  has  the  power  of  combining  with  acids  and  bases, 
and  the  hydrochloric  acid  combination  has  the  power  of  forming  a 
double  salt  with  platinic  chloride. 

Choline,  as  was  indicated  above,  is  one  of  the  decomposition 
products  of  lecithin.  It  is  trimethyl-hydroxy  ethyl- ammonium  hydroxide 
and  has  the  following  formula: 

CH2.CH2(OH) 

N-(CH3)3 

OH 

Researches  have  shown  that  great  importance  is  to  be  attached  to  the 
detection  of  choline  in  the  cerebro-spinal  fluid  and  the  blood  in  certain 
cases  of  degenerative  disease  of  the  nervous  system.  In  this  connec- 
tion tests  for  choline  (see  page  374)  are  of  interest  and  value. 

Protagon,  another  nitrogenous  phosphorized  substance,  is  a  body 
over  which  there  has  been  much  discussion.  Upon  decomposition  it 


372  PHYSIOLOGICAL  CHEMISTRY 

is  said  by  some  investigators  to  yield  cerebrin  and  the  decomposition 
products  of  lecithin.  It  has  been  shown  by  Posner  and  Gies1  as  well 
as  by  Rosenheim  and  Tebb2  that  protagon  is  a  mixture  and  has  no 
existence  as  a  chemical  individual.  Koch3  reported  data  obtained 
from  purified  preparations  which  indicate  that  protagon  contains  at 
least  three  substances:  a  "phosphatide  containing  cholin,  a  cerebro- 
side  containing  sugar,  a  complex  combination  of  a  cholin-free  phos- 
phatide with  a  cerebroside  to  which  an  ethereal  sulphuric  acid  group 
is  attached."  On  the  basis  of  his  data,  he  believed  the  term  pro- 
tagon to  have  no  chemical  significance.  He  proposed  the  term  sul- 
phatide.  Koch's  preparation  analyzed  as  follows  (per  cent) : 

Choline  Sugar  Nitrogen        Phosphorus        Sulphur 

i.o  12.0  2.3  1.7  i. 9 

He  suggested  the  following  structure: 

O 

II 

Phosphatide — 0 — S — 0 — Cerebroside 

grouping  grouping 

O 

Kephalin  is  the  third  member  of  the  group  of  phosphorized  fats. 
It  is  precipitated  from  its  acetone-ether  extract  by  alcohol.  It  contains 
about  4  per  cent  of  phosphorus  and  has  been  given  the  formula  C42Hy9- 
NPOis.  Kephalin  may  be  a  stage  in  lecithin  metabolism. 

The  cerebrosides  are  substances  containing  nitrogen  but  no  phos- 
phorus, and  are  important  constituents  of  the  white  matter  of  nervous 
tissue.  Certain  ones  have  also  been  found  in  the  spleen,  pus,  and  in  egg 
yolk.  They  may  be  extracted  from  the  tissue  by  boiling  alcohol  and  are 
insoluble  in  cold  alcohol,  cold  and  hot  ether,  and  in  water  and  dilute 
alkalis.  The  cerebroside  termed  cerebrin  is  a  mixture  containing  phre- 
nosin  (pseudo-cerebrin  or  cerebron),  a  body  yielding  the  carbohydrate 
galactose  on  decomposition. 

Cholesterol,  one  of  the  primary  cell  constituents,  is  present  in  fairly 
large  amount  in  nervous  tissue.  It  occurs  in  two  forms,  i.e.,  free  and 
combined  as  an  ester.  It  is  claimed4  that  99  per  cent  of  the  choles- 
terol of  brain  tissue  (boy)  it  in  the  free  state.  It  is  a  mon-atomic 
alcohol  containing  at  least  one  double  bond  and  possesses  the  formula 
C27H46OH  or  C27H43OH.  There  is  still  some  uncertainty  as  to  the 
exact  structure  of  cholesterol.  It  may  possess  a  terpene  structure.  It 

1  Posner  and  Gies:  Journal  of  Biological  Chemistry,  i,  59,  1905-06. 

2  Rosenheim  and  Tebb:  Journal  of  Physiology,  36  and  37,  1907-08. 

8  Koch:  Journal  Biological  Chemistry,  n,  March,  1912,  Proceedings. 
4Lapworth:  Jour.  Path.  Bad.,  1911,  p.  256. 


NERVOUS   TISSUE  373 

was  formerly  called  a  " non-saponifiable  fat"  but  since  it  is  not  changed 
in  any  way  by  boiling  alkalis  it  is  not  a  fat.  It  is  soluble  in  ether, 
chloroform,  benzene,  and  hot  alcohol.  It  crystallizes  in  the  form  of 
thin,  colorless,  transparent  plates  (Fig.  63,  page  213).  Cholesterol 
is  present  in  bile,  and  occurs  abundantly  in  one  form  of  biliary  calculus. 
It  is  also  present  in  blood  and  its  quantitative  determination  is  of 
clinical  importance  (see  Chapter  XVI).  It  has  been  found  in  feces, 
wool  fat,  egg  yolk,  and  milk,  frequently  in  the  form  of  its  esters  of 
higher  fatty  acids.  It  is  generally  believed  that  the  cholesterol  present 
in  the  animal  body  has  its  origin  in  the  vegetable  kingdom.  Some 
evidence  has  been  submitted1  indicating  a  synthesis  of  cholesterol 
under  certain  conditions  in  the  animal  body.  However,  it  is  probable 
that  cholesterol  is  not  readily  synthesized  in  the  body.2 

Paranucleoprotagon  is  a  phosphorized  substance  originally  isolated 
from  brain  tissue  by  Ulpiani  and  Lelli  and  recently  reinvestigated  by 
Steel  and  Gies.  It  is  said  to  possess  lecithoprot^in  characteristics. 

Nervous  tissue  yields  about  i  per  cent  of  ash  which  is  made  up  in 
great  part  of  alkaline  phosphates  and  chlorides. 

EXPERIMENTS  ON  THE  LIPOIDS  OF  NERVOUS  TISSUE 3 

1.  Preparation  of  Lecithin.4 — Treat  the  finely  divided  brain  of  a  sheep  with 
ether  and  allow  it  to  stand  in  the  cold  for  48-72  hours.    The  cold  ether  will  ex- 
tract lecithin  and  cholesterol.    Filter  and  add  acetone  to  the  filtrate  to  pre- 
cipitate the  lecithin.    Filter  off  the  lecithin  and  test  it  as  follows : 

(a)  Microscopical  Examination. — Suspend  a  small  portion  in  a   drop   of 
water  on  a  slide  and  examine  under  the  microscope. 

(b)  Osmic  Acid  Test.5— Treat  a  small  portion  with  osmic  acid.    What 
happens? 

(c)  Acrolein  Test. — Make  the  acrolein  test  according  to  directions  on  page 
184. 

(d)  Test  for  Phosphorus.— See  page  128,  Chapter  VI. 

2.  Preparation  of  Cholesterol. — Place  a  small  amount  of  finely  divided  brain 
tissue  under  ether  and  stir  occasionally  for  one  hour.    Filter,  evaporate  the 
filtrate  to  dryness  on  a  water-bath,  and  test  the  cholesterol  according  to  direc- 
tions given  below.     (If  it  is  desired,  the  ether  extract  from  the  so-called  protagon, 

1  Klein:  Biochem.  Zeit.,  30,  465,  1910. 

2  Gardner  and  Lander:  Proc.  Royal  Soc.^  London  (B),  87,  229,  1913. 
^Preparation  oj  So-called  Protagon. — Divide  the  brain  of  a  sheep  into  small  pieces, 

treat  with  85  per  cent  alcohol  and  warm  on  a  water-bath  45°C.  for  two  hours.  Filter  hot 
into  a  bottle  or  strong  flask  and  cool  to  o°C.  for  one-half  hour,  by  means  of  a  freezing  mix- 
ture. By  this  procedure  both  protagon  and  cholesterol  are  caused  to  precipitate.  Filter 
the  cold  solution  rapidly  and  treat  the  precipitate  on  the  paper  with  ice  cold  ether  to  dis- 
solve out  the  cholesterol.  The  protagon  may  now  be  redissolved  in  warm  85  per  cent 
alcohol  from  which  solution  it  will  precipitate  upon  cooling. 

4  For  the  preparation  of  lecithin  in  purer  form  see  MacLeon:  Jour.  Path.  Bact.,  18,  490, 
1914. 

6  Osmic  acid  serves  to  detect  fats  which  contain  un^atur ated  fatty  acid  jradicals,  e.g., 
oleic  add,  in  their  molecule. 


374  PHYSIOLOGICAL  CHEMISTRY 

or  the  ether-acetone  filtrate  from  the  lecithin  may  be  used  for  the  isolation  of 
cholesterol.  In  these  cases  it  is  simply  necessary  to  evaporate  the  solution  to 
dryness  on  a  water-bath.)  Upon  the  cholesterol  prepared  by  either  of  the  above 
methods  make  the  following  tests : 

(a)  Microscopical  Examination. — Examine  the  crystals  under  the  microscope 
and  compare  them  with  those  in  Fig.  63,  page  213. 

(b)  H2SO4  Test  (Salkowski). — Dissolve  a  few  crystals  of  cholesterol  in  a 
little  chloroform  and  add  an  equal  volume  of  concentrated  sulphuric  acid.    A 
play  of  colors  from  bluish-red  to  cherry-red  and  purple  is  noted  in  the  chloro- 
form, while  the  acid  assumes  a  marked  green  fluorescence. 

(c)  Acetic  Anhydride-H2SO4  Test  (Liebermann-Burchard). — Dissolve  a  few 
crystals  of  cholesterol  in  2  c.c.  of  chloroform  in  a  dry  test-tube.    Now  add  10 
drops  of  acetic  anhydride  and  1-3  drops  of  concentrated  sulphuric  acid.    The 
solution  becomes  red,  then  blue,  and  finally  bluish-green  in  color. 

(d}  Iodine-sulphuric  Acid  Test. — Place  a  few  crystals  of  cholesterol  in  one  of 
the  depressions  of  a  test-tablet  and  treat  with  a  drop  of  concentrated  sulphuric  acid 
and  a  drop  of  a  very  dilute  solution  of  iodine.  A  play  of  colors,  consisting  of  violet, 
blue,  green,  and  red,  results. 

(e)  Schiff's  Reaction. — To  a  little  cholesterol  in  an  evaporating  dish  add  a  few 
drops  of  a  reagent  made  by  adding  i  volume  of  10  per  cent  ferric  chloride  to  3  vol- 
umes of  concentrated  sulphuric  acid.  Evaporate  to  dryness  over  a  low  flame  and 
observe  the  reddish-violet  residue  which  changes  to  a  bluish-violet. 

(/)  Phosphorus. — Test  for  phosphorus  according  to  directions  given  in  Chapter 
VI,  page  128.  Is  phosphorus  present? 

3.  Preparation  of  Cerebrin. — Treat  100  grams  of  finely  divided  brain  tissue, 
in  a  flask,  with  200  c.c.  of  95  per  cent  alcohol  and  boil  on  a  water-bath  for  one- 
half  hour,  keeping  the  volume  constant  by  adding  fresh  alcohol  as  needed  or  by 
the  use  of  a  reflux  condenser.  Filter  the  solution  hot  and  stand  the  cloudy 
filtrate  away  for  24  hours.  (If  the  filtrate  is  not  cloudy  concentrate  it  upon  the 
water-bath  until  it  is  so.)  Filter  off  the  cerebrin  (cerebrin,  lecithin,  kephalin, 
cholesterol)  and  test  it  as  follows : 

(a)  Microscopical  Examination. — Suspend  a  small  portion  in  a  drop  of  water 
on  a  slide  and  examine  under  the  microscope. 

(b)  Solubility. — Try  the  solubility  of  cerebrin  in  water,  10  per  cent  sodium 
chloride  and  in  dilute  acid  and  alkali,  and  in  hot  and  cold  alcohol  and  hot  and 
cold  ether. 

(c)  Phosphorus. — Test  for  phosphorus  according  to  directions  in  Chapter 
VI,  page  128.    How  does  the  result  compare  with  that  on  lecithin? 

(d)  Place  a  little  cerebrin  on  platinum  foil  and  warm.    Note  the  odor. 

(e)  Hydrolysis  of  Cerebrin. — Place  the  remaining  cerebrin  hi  a  small  evapo- 
rating dish,  add  equal  volumes  of  water  and  dilute  hydrochloric  acid,  and  boil 
for  one  hour.    Cool,   neutralize  with  solid  potassium  hydroxide,  filter,  and 
test  with  Fehling's  solution.    Is  there  any  reduction,  and  if  so  how  do  you 
explain  it? 

(4.  Tests  for  Choline. — (a)  Rosenheim's  Periodide  Test. — Prepare  an  alcoholic 
extract  of  the  fluid  under  examination,  and  after  evaporation  apply  Rosenheim's 
iodo-potassium  iodide  solution1  to  a  little  of  the  residue.  In  a  short  time  dark 

1  Prepared  by  dissolving  2  grains  of  iodine  and  6  grams  of  potassium  iodide  in  100  c.c. 
water. 


NERVOUS    TISSUE  375 

brown  plates  and  prisms  of  choline  periodide  begin  to  form  and  may  be  detected  by 
means  of  the  microscope.  Occasionally  they  are  large  enough  to  be  visible  to  the 
naked  eye.  They  somewhat  resemble  crystals  of  hemin  (see  page  268).  If  the 
slide  be  permitted  to  stand,  thus  allowing  the  fluid  to  evaporate,  the  crystals  will 
disappear  and  leave  brown  oily  drops.  They  will  reappear,  however,  upon  the 
addition  of  fresh  iodine  solution,  v.  Stanek  claims  that  this  choline  compound 
has  the  formula  C8Hi4NOI.I8. 

(b)  Rosenheim's  Bismuth  Test. — Extract  the  fluid  under  examination  with 
absolute  alcohol,  evaporate,  and  reextract  the  residue.  Repeat  the  extraction 
several  times.  Dissolve  the  final  residue  in  2-3  c.c.  of  water  and  add  a  drop  of 
Kraut's  reagent.1  Choline  is  indicated  by  the  appearance  of  a  bright  brick-red 
precipitate. 

1  Dissolve  272  grams  of  potassium  iodide  in  water  and  add  80  grams  of  bismuth  sub- 
nitrate  dissolved  in  200  grams  of  nitric  acid  (sp.  gr.  i  .18).  Permit  the  potassium  nitrate  to 
crystallize  out,  then  filter  it  off  and  make  the  filtrate  up  to  i  liter  with  water. 


CHAPTER  XXII 

URINE:    GENERAL    CHARACTERISTICS    OF    NORMAL    AND 
PATHOLOGICAL  URINE 

Volume. — The  volume  of  urine  excreted  by  normal  individuals 
during  any  definite  period  fluctuates  within  very  wide  limits.  The 
average  output  for  twenty-four  hours  is  placed  by  German  writers 
between  1500  and  2000  c.c.  This  value  is  not  strictly  applicable  to  con- 
ditions in  America,  however,  since  it  has  been  found  that  the  average 
normal  excretion  of  the  adult  male  American  falls  within  the  lower 
values  of  1000-1200  c.c.  The  volume-excretion  is  influenced  greatly 
by  the  diet,  particularly  by  the  ingestion  of  fluids. 

Certain  pathological  conditions  cause  the  output  of  urine  for  any 
definite  period  to  depart  very  decidedly  from  the  normal  output. 
Among  the  pathological  conditions  in  which  the  volume  of  urine  is  in- 
creased above  normal  are  the  following:  Diabetes  mellitus,  diabetes 
insipidus,  certain  diseases  of  the  nervous  system,  contracted  kidney, 
amyloid  degeneration  of  the  kidney,  and  in  convalescence  from  acute 
diseases  in  general.  Many  drugs  such  as  calomel,  digitalis,  acetates, 
and  salicylates  also  increase  the  volume  of  the  urine  excreted.  A 
decrease  from  the  normal  is  observed  in  the  following  pathological 
conditions:  Acute  nephritis,  diseases  of  the  heart  and  lungs,  fevers, 
diarrhcea,  and  vomiting. 

Color. — Normal  urine  ordinarily  possesses  a  yellow  tint,  the  depth 
of  the  color  being  dependent  in  part  upon  the  density  of  the  fluid.  The 
color  of  normal  urine  is  due  principally  to  a  pigment  called  urochrome;1 
traces  of  hematoporphyrin,  urobilin,  and  uroerythrin  have  also  been 
detected.  Under  pathological  conditions  the  urine  is  subject  to  pro- 
nounced variations  in  color  and  may  contain  many  varieties  of  pig- 
ments. Under  such  circumstances  the  urine  may  vary  in  color  from  an 
extremely  light  yellow  to  a  very  dark  brown  or  black.  Vogel  has  con- 
structed a  color  chart  which  is  of  some  value  for  purposes  of  comparison. 
The  nature  and  origin  of  the  chief  variations  in  the  urinary  color  are  set 
forth  in  tabular  form  by  Halliburton  as  follows: 

1  Urochrome  is  believed  to  be  identical  with  the  yellow  pigment  (lactochrome)  of  milk 
whey  (Palmer  and  Coolidge:  Jour.  BioL  Chem.,  17,  251,  1914). 

376 


URINE 


377 


Color 

Cause  of  coloration 

Pathological  condition 

Nearly  colorless 

Dilution,   or   diminution   of 

Nervous      conditions  :      hy- 

normal  pigments. 

druria,   diabetes  insipidus, 
granular  kidney. 

Dark  yellow  to  brown-red  . 

Increase  of  normal,  or  oc- 
currence   of    pathological, 
pigments.        Concentrated 
urine. 

Acute  febrile  diseases. 

Milky  

Chyluria. 

Pus  corpuscles     .... 

Purulent     diseases     of     the 

urinary  tract. 

Orange 

Excreted  drugs  

Santonin,  crysophanic  acid. 

Red  or  reddish  

Hematoporphyrin  

Hemorrhages,    or    hemoglo- 

Unchanged  hemoglobin.  . 

binuria. 

Pigments  in  food  (logwood, 
madder,  bilberries,  fuchsin). 

Brown  to  brown  black. 

Hematin  

Small  hemorrhages. 

Methemoglobin  

M  ethemoglobinuria  . 

•  *                      •'••-. 

Melanin 

Melanotic  sarcoma. 

Hydrochinol  and  catech*ol  .  .  . 

Carbolic-acid  poisoning. 

Greenish  yellow,  greenish 

Bile-pigments  

Jaundice. 

brown,  approaching  black. 

Dirty  green1  or  blue.  .    .  . 

A  dark  blue  scum  on  surface, 

Cholera,  typhus;  seen  espe- 

with a  blue  deposit,  due  to 
an  excess  of  indigo-forming 
substances. 

cially    when   the   urine   is 
putrefying. 

Brown-yellow  to  red-brown, 
becoming  blood-red  upon 
adding  alkalis. 

Substances      contained     in 
senna,  rhubarb   and  cheli- 
donium    which    are    intro- 
duced into  the  system. 

Transparency. — Normal  urine  is  ordinarily  perfectly  clear  and 
transparent  when  voided.  On  standing  for  a  variable  time,  however,  a 
cloud  (nubecula)  consisting  principally  of  nucleoprotein  or  mucoid  (see 
page  413)  and  epithelial  cells  forms.  A  turbidity  due  to  the  precipita- 
tion of  phosphates  is  normally  noted  in  urine  passed  after  a  hearty 

1  This  dirty  green  or  blue  color  also  occurs  after  the  use  of  methylene  blue  in  the 
organism. 


378  PHYSIOLOGICAL   CHEMISTRY 

meal.  The  urine  obtained  2-3  hours  after  a  meal  or  later  is  ordinarily 
free  from  turbidity.  Permanently  turbid  urines  ordinarily  arise  from 
pathological  conditions. 

Odor. — The  odor  of  normal  urine  is  of  a  faint,  aromatic  type.  The 
bodies  to  which  this  odor  is  due  are  not  well  known,  but  it  is  claimed  by 
some  investigators  to  be  due,  at  least  in  part,  to  the  presence  of  minute 
amounts  of  certain  volatile  organic  acids.  Dehn  and  Hartman1  have 
recently  succeeded  in  isolating  from  urine  a  neutral  ill-smelling  substance 
which  they  call  urinod.  Its  empirical  formula  is  CeH80.  Urinod  occurs 
in  urine  to  the  extent  of  only  1-2  parts  in  100,000  parts  of  urine. 
When  the  urine  undergoes  decomposition,  e.g.,  in  alkaline  fermentation, 
a  very  unpleasant  ammoniacal  odor  is  evolved.  All  urines  are  subject 
to  such  decomposition  if  allowed  to  stand  for  a  sufficiently  long  time. 
Under  normal  conditions  the  urine  very  often  possesses  a  peculiar  odor 
due  to  the  ingestion  of  some  certain  drug  or  vegetable.  For  instance, 
cubebs,  copaiba,  myrtol,  saffron,  tolu,  and  turpentine  each  imparts  a 
somewhat  specific  odor  to  the  urine.  After  the  ingestion  of  asparagus, 
the  urine  also  possesses  a  typical  odor  due  to  the  presence  of  methyl 
mercaptan  (CH3  SH)  which  is  formed  in  the  intestine  and  eliminated 
in  the  urine. 

Frequency  of  Urination. — The  frequency  of  urination  varies  greatly 
in  different  individuals,  but  in  general  is  dependent  upon  the  amount  of 
fluid  in  the  bladder.  In  pathological  conditions  an  inflammatory  affec- 
tion of  the  urinary  tract  or  any  disturbance  of  the  innervation  of  the 
bladder  will  influence  the  frequency.  Affections  of  the  spinal  cord 
which  lead  to  an  increased  irritability  of  the  bladder  or  a  weakening  of 
the  sphincter,  or  any  condition  lowering  the  residual  capacity  of  the 
bladder,  will  result  in  increasing  the  frequency  of  urination. 

Reaction. — The  mixed  24-hour  urinary  excretion  of  a  normal  indi- 
vidual ordinarily  possesses  an  acid  reaction  to  litmus.  This  acidity  in 
normal  cases  is  represented  on  the  average  by  a  hydrogen  ion  concentra- 
tion of  10  X  io~~ 7,  although  it  may  vary  from  0.40  to  150  X  io~ 7.  The 
reaction  of  the  urine  represents  an  equilibrium  between  a  large  number 
of  acid  and  basic  constituents,  both  organic  and  inorganic,  which  it  con- 
tains. Although  organic  acids  and  bases  play  a  part  in  producing  the 
normal  reaction,  this  reaction  is  probably,  in  the  main,  dependent  upon 
the  relative  amounts  of  the  mono-  and  dibasic  sodium  and  potassium 
phosphates  present.  The  monobasic  sodium  phosphate  (NaH2P04) 
is  acid  in  reaction,  while  the  dibasic  phosphate  (Na2HPC>4)  is  alkaline 
in  reaction.  The  excretion  of  acid  or  alkaline  phosphate  by  the  kidneys 
is  one  of  the  factors  in  the  regulation  of  the  neutrality  of  the  blood  and  of 

1  Dehn  and  Hartman:  Jour.  Am.  Chem.  Soc.  36,  2136,  1914, 


URINE 


379 


the  organism  in  general.  The  acidity  of  the  urine  as  determined  by 
titration  runs  in  general  parallel  with  the  hydrogen  ion  concentration 
and  seems  to  be  dependent  upon  the  same  factors,  and  in  more  acid 
urines  mainly  on  the  phosphate  content.  Van  Slyke  and  Palmer1  have 
shown  that  normal  men  excrete  organic  acids  equivalent  to  only  about 
6  c.c.  of  o.i  N  acid  in  twenty-four  hours.  (For  further  discussion  of 
acidity  see  Chapter  VIII  on  Gastric  Analysis.) 

The  mean  acidity  in  cardio-renal  diseases  is  high — about  50  X  io~7 
as  compared  with  10  X  io~7,  the  normal  mean.  In  general  the  acidity 
tends  to  be  increased  in  the  greater  number  of  pathological  disorders. 

The  composition  of  the  food  is  perhaps  the  most  important  factor 
in  determining  the  reaction  of  the  urine  (see  Chapter  XXVIII  on  Met- 
abolism for  influence  of  base-forming  and  acid-forming  foods).  The 
reaction  ordinarily  varies  considerably  according  to  the  time  of  day 
the  urine  is  passed.  For  instance,  for  a  variable  length  of  time  after 
a  meal  the  urine  may  be  neutral  or  even  alkaline  in  reaction  to  litmus, 


FIG.  119. — DEPOSIT  IN  AMMONIACAL  FERMENTATION. 
a,  Acid  ammonium  urate;  b,  ammonium  magnesium  phosphate;  c,  bacteria. 

owing  to  the  claim  of  the  gastric  juice  upon  the  acidic  radicals  to  further 
the  formation  of  hydrochloric  acid  for  use  in  carrying  out  the  digestive 
secretory  function.  This  change  in  reaction  is  known  as  the  alkaline 
tide  and  is  common  to  perfectly  healthy  individuals.  The  urine  may 
also  become  temporarily  alkaline  in  reaction  to  litmus,  as  the  result  of 
ingesting  alkaline  carbonates  or  certain  salts  of  tartaric  and  citric  acids 
which  may  be  transformed  into  carbonates  within  the  organism. 
Normal  urine  upon  standing  for  some  time  becomes  alkaline  in  reaction 
to  litmus,  owing  to  the  inception  of  alkaline  or  ammoniacal  fermentation 
through  the  agency  of  micro-organisms.  This  fermentation  has  no 
especial  diagnostic  value  except  in  cases  where  the  urine  has  undergone 

VVan  Slyke  and  Palmer:  Jour.  Biol.  Chem.,  41,  567,  1920. 


38o 


PHYSIOLOGICAL   CHEMISTRY 


this  change  within  the  organism  and  is  voided  in  the  decomposed  state. 
Ammoniacal  fermentation  is  ordinarily  due  to  cystitis  or  occurs  as  the 
result  of  infection  in  the  process  of  catheterization.  A  microscopical 
examination  of  such  urine  (Fig.  119)  shows  the  presence  of  ammonium 
magnesium  phosphate  crystals,  amorphous  phosphates,  and  not  infre- 
quently ammonium  urate. 

Ingestion  of  acid  fruits  (oranges,  lemons,  peaches,  etc.)  causes 
the  formation  of  alkaline  urine.  This  is  due  to  the  fact  that  the  ash  of 
such  fruits  is  alkaline  and  when  the  fruits  are  combusted  in  the  body 
carbonates  are  formed.  On  the  other  hand,  bread,  cereals,  meats,  etc., 
yield  an  acid  ash  and  an  acid  urine. 

Occasionally  a  urine  which  possesses  a  normal  acidity  when  voided, 
upon  standing  instead  of  undergoing  ammoniacal  fermentation  as  above 
described,  will  become  more  strongly  acid  in  reaction.  Such  a  phe- 
nomenon is  termed  acid  fermentation.  Accompanying  this  increased 
acidity  there  is  ordinarily  a  deepening  of  the  tint  of  the  urinary  color. 


FIG.  120. — DEPOSIT  IN  ACID  FERMENTATION. 
a,  Fungus;  b,  amorphous  sodium  urate;  c,  uric  acid;  d,  calcium  oxalate. 

Such  urines  may  contain  acid  urates,  uric  acidjungi,  and  calcium  oxalate 
(Fig.  120,  above).  On  standing  for  a  sufficiently  long  time  any  urine 
which  exhibits  acid  fermentation  will  ultimately  change  in  reaction, 
due  to  the  inception  of  alkaline  fermentation,  and  will  show  the  micro- 
scopical deposits  characteristic  of  such  a  urine. 

Specific  Gravity. — The  specific  gravity  of  the  urine  of  normal  indi- 
viduals varies  ordinarily  between  1.015  and  1.025.  This  value  is  sub- 
ject to  wide  fluctuations  under  various  conditions.  For  instance, 
following  copious  water-  or  beer-drinking  the  specific  gravity  may  fall 
to  1.003  or  lower,  whereas  in  cases  of  excessive  perspiration  it  may  rise 
as  high  as  1.040  or  even  higher.  Where  a  very  accurate  determina- 
tion of  the  specific  gravity  is  desired,  use  is  commonly  made  of  the 
pyknometer  or  of  the  Westphal  hydrostatic  balance.  These  instruments, 


URINE 


however,  are  not  suited  for  clinical  use.  The  clinical  method  of  deter- 
mining the  specific  gravity  is  by  means  of  a  urinometer  (Fig.  121).  This 
affords  a  very  rapid  method  and  at  the  same  time  is  sufficiently  accurate 
for  clinical  purposes.  The  urinometer  is  always  calibrated  for  use  at  a 
specific  temperature  and  the  observations  made  at  any  other  tem- 
perature must  be  subjected  to  a  certain  correction  to  obtain  the  true 
specific  gravity.  In  making  this  correction  one  unit  of  the  last  order  is 
added  to  the  observed  specific  gravity  for  every  three  degrees  above 
the  normal  temperature  and  subtracted  for  every  three 
degrees  below  the  normal  temperature.  For  instance, 
if  in  using  a  urinometer  calibrated  for  i5°C.  the  specific 
gravity  of  a  urine  having  a  temperature  of  2i°C.  is 
determined  as  1.018  it  is  necessary  to  add  to  the 
observed  specific  gravity  two  units  of  the  third  order 
to  obtain  the  real  specific  gravity  of  the  urine.  There- 
fore the  true  specific  gravity,  at  i5°C.,  of  a  urine 
having  a  specific  gravity  of  1.018  at  2i°C.  is  1.618  + 
0.002  =  i. 020. 

Pathologically,  the  specific  gravity  may  be  sub- 
jected to  very  wide  variations.  This  is  especially 
true  in  diseases  of  the  kidneys.  In  acute  nephritis 
ordinarily  the  urine  is  concentrated  and  of  a  high 
specific  gravity,  whereas  in  chronic  nephritis  the  re- 
verse conditions  are  more  apt  to  prevail.  In  fact, 
under  most  conditions,  whether  physiological  or  patho- 
logical, the  specific  gravity  of  the  urine  is  inversely 
proportional  to  the  volume  excreted.  This  is  not 
true  of  diabetes  mellitus,  however,  where  the  volume 
of  urine  is  large  and  the  specific  gravity  is  also  high, 
owing  to  the  sugar  contained  in  the  urine. 

The  amount  of  solids  eliminated  in  the  excretion 
for  twenty-four  hours  may  be  roughly  calculated  by  ™ETER  AND  CYLIN- 
means  of  Long's  coefficient,  i.e.,  2.6.  The  solid  con- 
tent of  1000  c.c.  of  urine  is  obtained  by  multiplying  the  last  two 
figures  of  the  specific  gravity  observed  at  25°C.  by  2.6.  To  determine 
the  amount  of  solids  excreted  in  twenty-four  hours  if  the  volume  was 
1 1 20  c.c.  and  the  specific  gravity  was  1.018  the  calculation  would  be  as 
follows : 

(a)  18  X  2.6  =  46.8  grams  of  solid  matter  in  1000  c.c.  of  urine. 

/046.8  X  H20 


FIG.  121. — URIN- 


IOOO 


52.4  grams  of  solid  matter  in  1120  c.c.  of  urine. 


The  coefficient  of  Haser  (2.33)  which  has  been  in  use  for  years  prob- 
ably gives  values  that  are  inaccurate  for  conditions  existing  in  America. 


382 


PHYSIOLOGICAL   CHEMISTRY 


This  coefficient  was  calculated  on  the  basis  of  the  specific  gravity  deter- 
mined at  a  temperature  of  i5°C. 

Freezing-point  (Cryoscopy). — The  freezing-point  of  a  solution  de- 
pends upon  the  total  number  of  molecules  of  solid  matter  dissolved  in 

it.  The  determination  of  the  osmotic  pressure 
by  this  method  has  come  to  be  of  some  clinical 
importance,  particularly  as  an  aid  in  the  diag- 
nosis of  kidney  disorders.  In  this  connection 
it  is  best  to  collect  the  urine  from  each  kidney 
separately  and  determine  the  freezing-point  in 
the  individual  samples  so  collected.  By  this 
means  considerable  aid  in  the  diagnosis  of  renal 
diseases  may  be  secured.  The  fluids  most  fre- 
quently examined  cryoscopically  are  the  blood 
(see  page  248)  and  the  urine.  The  freezing- 
point  is  denoted  by  A.  The  value  of  A  for 
normal  urine  varies  ordinarily  between  —1.3° 
and  —  2.3°C.,  the  freezing-point  of  pure  water 
being  taken  as  o°.  A  is  subject  to  very  wide 
fluctuations  under  unusual  conditions.  For 
instance,  following  copious  water-  or  beer- 
drinking  A  may  have  as  high  a  value  as 

—  o.2°C.,  whereas  on  a  diet  containing  much 
salt  and  deficient  in  fluids  the  value  of  A  may 
be  lowered  to  —  3°C.  or  even  lower.     The  freez- 
ing-point of  normal  blood  is  generally  about 

—  o  .56°C.    and   is    not    subject    to  "the   wide 
variations  noted  in  the  urine,  because  of  the 
tendency   of    the    organism    to    maintain    the 
normal  osmotic  pressure  of  the  blood  under  all 
conditions.     Variations   between    —0.51°    and 
— o.62°C.  may  be  due  entirely  to  dietary  con- 
ditions, but  if  any  marked  variation  is  noted 
it  can,  in  most  cases,  be  traced  to  a  disordered 
kidney  function. 

Freezing-point  determinations  may  be  made 
by  means  of  the  Beckmann-Heidenhain  appa- 
ratus (Fig.  122)  or  the  Zikel  pektoscope.  The 
Beckmann-Heidenhain  apparatus  consists  of 
the  following  parts:  A  strong  battery  jar  or  beaker  (C)  furnished 
with  a  metal  cover  which  is  provided  with  a  circular  hole  in  its  center. 
This  strong  glass  vessel  serves  to  hold  the  freezing  mixture  by  means 


FIG.  122. — BECKMANN- 
HEIDENHAIN  FREEZING- 
POINT  APPARATUS.  (Long.) 

D,  a  delicate  thermom- 
eter; C,  the  containing 
jar;  B,  the  outside  or  air 
mantle  tube;  A,  the  tube  in 
which  the  mixture  to  be 
observed  is  placed.  Two 
stirrers  are  shown,  one  for 
the  cooling  mixture  in  the 
jar  and  one  for  the  experi- 
mental mixture. 


URINE  383 

of  which  the  temperature  of  the  fluid  under  examination  is  lowered. 
A  large  glass  tube  (B)  designed  as  an  air-jacket,  and  formed  after  the 
manner  of  a  test-tube  is  introduced  through  the  central  aperture  in  the 
metal  cover  and  into  this  air-jacket  is  lowered  a  smaller  tube  (A)  con- 
taining the  fluid  to  be  tested.  A  very  delicate  thermometer  (D),  gradu- 
ated in  hundredths  of  a  degree  is  introduced  into  the  inner  tube  and 
is  held  in  place  by  means  of  a  cork  so  that  the  mercury  bulb  is  im- 
mersed in  the  fluid  under  examination  but  does  not  come  into  contact 
with  any  glass  surface.  A  small  platinum  wire  stirrer  serves  to  keep 
the  fluid  under  examination  well  mixed  while  a  larger  stirrer  is  used  to 
manipulate  the  freezing  mixture.  (Rock  salt  and  ice  in  the  .proportion 
1:3  form  a  very  satisfactory  freezing  mixture.) 

In  making  a  determination  of  the  freezing-point  of  a  fluid  by  means 
of  the  Beckmann-Heidenhain  apparatus  proceed  as  follows:  Place 
the  freezing  mixture  in  the  battery  jar  and  add  water  (if  necessary)  to 
secure  a  temperature  not  lower  than  3°C.  Introduce  the  fluid  to  be 
tested  into  tube  A,  place  the  thermometer  and  platinum  wire  stirrer  in 
position,  and  insert  the  tube  into  the  air-jacket  which  has  previously 
been  inserted  through  the  metal  cover  of  the  battery  jar.  Manipulate 
the  two  stirrers  in  order  to  insure  an  equalization  of  temperature 
and  observe  the  course  of  the  mercury  column  of  the  thermometer  very 
carefully.  The  mercury  will  gradually  fall  and  this  gradual  lowering 
of  the  temperature  will  be  followed  by  a  sudden  rise.  The  point  at 
which  the  mercury  rests  after  this  sudden  rise  is  the  freezing-point. 
This  rise  is  due  to  the  fact  that  previous  'to  freezing,  a  fluid  is  always 
more  or  less  over-cooled  and  the  thermometer  temporarily  registers  a 
temperature  somewhat  below  the  freezing-point.  As  the  fluid  freezes, 
however,  there  is  a  very  sudden  change  in  the  temperature  of  the  liquid 
and  this  change  is  imparted  to  the  thermometer  and  causes  the  rise  as 
indicated.  It  occasionally  occurs  that  the  fluid  under  examination  is 
very  much  over-cooled  and  does  not  freeze.  Under  such  circumstances 
a  small  piece  of  ice  is  introduced  into  it  by  means  of  the  side  tube  noted 
in  the  figure.  This  so-called  "inoculation"  causes  the  fluid  to  freeze 
instantaneously.  (For  details  of  the  method  of  determining  the 
freezing-point  consult  standard  works  on  physical  or  organic  chemistry.) 

Electrical  Conductivity. — The  electrical  conductivity  of  the  u 
is  dependent  upon  the  number  of  inorganic  molecules  or  ions  present, 
and  in  this  differs  from  the  freezing-point  which  is  dependent  upon  the 
total  number  of  molecules  both  inorganic  and  organic  which  are  in 
solution.  The  conductivity  of  the  urine  has  been  investigated  but 
slightly,  but  from  the  data  secured  it  seems  that  the  value  generally 
falls  below  K  =  0.03.  The  conductivity  of  blood  serum  has  been  de- 


384  PHYSIOLOGICAL  CHEMISTRY 

termined  as  K  =  0.012.  Up  to  the  present  time  the  determination  of 
the  electrical  conductivity  of  any  of  the  fluids  of  the  body  has  been 
put  to  very  slight  clinical  use.  Experience  may  show  the  conductivity 
value  to  be  a  more  important  aid  to  diagnosis  than  it  is  now  considered, 
particularly  if  it  is  taken  in  connection  with  the  determination  of  the 
freezing-point.  By  a  combination  of  these  two  methods  the  portion 
of  the  osmotic  pressure  due  respectively  to  electrolytes  and  non- 
electrolytes  may  be  determined.  For  a  discussion  of  electrical  con- 
ductivity, the  method  by  which  it  is  determined,  and  the  principles 
involved  consult  standard  works  on  physical  or  electro-chemistry. 

Collection  and  Preservation  of  the  Urine  Sample. — If  any  depend- 
able data  are  desired  regarding  the  quantitative  composition  of  the  urine 
the  examination  of  the  mixed  excretion  for  twenty-four  hours  is  ab- 
solutely necessary.  In  collecting  the  urine  the  bladder  may  be  emptied 
at  a  given  hour,  say  8  A.  M.,  the  urine  discarded  and  all  the  urine  from 
that  hour  up  to  and  including  that  passed  the  next  day  at  8  A.  M., 
saved,  thoroughly  mixed,  and  a  sample  taken  for  analysis.  Until 
recently  it  was  believed  that  powdered  thymol  (para-isopropylmetacresol) 

CH3 


'OH 

CH3— CH— CH3, 

was  a  very  satisfactory  preservative  since  the  excess  might  be  removed 
by  nitration,  if  desired,  and  it  was  believed  that  the  small  amount  which 
went  into  solution  would  have  no  appreciable  influence  upon  the  deter- 
mination of  any  of  the  urinary  constituents.  It  appears  however  that 
thymol  is  not  such  a  satisfactory  urinary  preservative  as  was  believed. 
Evidence  has  been  presented  showing  it  to  be  unsatisfactory  for  the 
preservation  of  urines  which  contain  sugar,  acetone  or  diacetic  acid, 
and  in  which  it  is  desired  to  estimate  the  quantitative  content  of  these 
constituents.  Claim  has  also  been  made  that  thymol  is  not  a  satis- 
factory preservative  for  urines  that  are  to  be  examined  quantitatively  for 
phosphates  or  magnesium.  Thymol  being  a  phenol  will  cause  an  in- 
accuracy when  phenols  are  being  determined  quantitatively.  Urines 
preserved  by  thymol  will  also  give  a  confusing  white  ring  when  sub- 
jected to  the  nitric  acid  test  for  albumin  (see  Chapter  XXIV). 

Toluene  is  a  very  satisfactory  preservative  for  urine.     In  using  this 
preservative  simply  overlay  the  urine  with  the  toluene.     Rosenbloom1 

1  Rosenbloom:  New  York  Medical  Journal,  99,  735,  1914. 


URINE  385 

claims  that  camphor  is  a  very  satisfactory  urine  preservative  which 
does  not  interfere  with  the  tests  for  important  urinary  constituents. 

In  certain  pathological  conditions  it  is  desirable  to  collect  the  urine 
passed  during  the  day  separately  from  that  passed  during  the  night. 
When  this  is  done  the  urine  voided  between  8  A.  M.  and  8  P.  M.  may 
be  taken  as  the  day  sample  and  that  voided  between  8  P.  M.  and  8.  A.  M. 
as  the  night  sample. 

The  qualitative  testing  of  urine  samples  collected  at  random,  except 
in  a  few  specific  instances,  is  of  no  particular  value  so  far  as  giving  us 
any  accurate  knowledge  as  to  the  exact  urinary  characteristics  of  the 
individual  is  concerned.  In  the  great  majority  of  cases  the  qualitative 
as  well  as  the  quantitative  tests  should  be  made  upon  the  mixed 
excretion  for  a  twenty-four-hour  period  as  well  as  upon  a  night  sample 
as  above  described. 


CHAPTER  XXII 


URINE :  PHYSIOLOGICAL  CONSTITUENTS1 
i.  Organic  Physiological  Constituents 


Urea. 
Uric  acid. 
Creatinine. 
Creatine.2 

Ethereal  sulphuric  acids 


Hippuric  acid. 
Oxalic  acid. 


Indoxyl-sulphuric  acid. 
Phenol-  and  ^-cresol-sulphuric  acids. 
Pyrocatechol-sulphuric  acid. 
Skatoxyl-sulphuric  acid. 


Neutral  sulphur  compounds, 


Allan  toin. 


Aromatic  oxyacids, 


Cystine. 

Chondroi tin-sulphuric  acid. 

Thiocyanates. 

Taurine  derivatives. 

Oxyproteic  acid. 

Alloxyproteic  acid. 

Uroferric  acid. 

Para-oxyphenyl-acetic  acid. 

Para-oxyphenyl-propionic  acid. 

Homogentisic  acid. 

Uroleucic  acid. 

Oxymandelic  acid. 

Kynurenic  acid. 
Amino-acids. 
Peptides. 
Benzoic  acid. 
Nucleoprotein. 
Oxaluric  acid. 
Glucose. 

1  It  is  impossible  to  make  any  absolute  classification  of  the  physiological  and  pathologica 
constituents  of  the  urine.     A  substance  may  be  present  in  the  urine  in  small  amount  physio- 
logically and  be  sufficiently  increased  under  certain  conditions  as  to  be  termed  a  patholog- 
ical constituent.     Therefore  it  depends,  in  some  instances  upon  the  quantity  of  a  constituent 
present  whether  it  may  be  correctly  termed  a  physiological  or  a  pathological  constituent. 

2  Normal  constituent  of  urine  of  adults  but  found  in  larger  amount  in  urine  of  infants 
and  children  (see  p.  529). 

386 


URINE 


387 


Pepsin. 
Enzymes Gastric  rennin. 

Amylase. 

Acetic  acid. 
Volatile  fatty  acids. Butyric  acid. 

Formic  acid. 
Paralactic  acid. 
Phenaceturic  acid. 
Urocanic  acid. 

Phosphorized  compounds .... 


Pigments 

Ptomaines  and  leucomaines. 


Glycerophosphoric  acid. 
Phosphocarnic  acid. 
Urochrome. 
Urobilin. 
Uroerythrin. 


Adenine. 
Guanine. 
Xan  thine. 

- 

Epiguanine. 

Purine  Bases I  Episarkine. 

Hypoxanthine. 
Paraxanthine. 
He  teroxan  thine . 
i  -Methylxan  thine. 

2.  Inorganic  Physiological  Constituents 

Ammonia. 

Sulphates. 

Chlorides.      • 

Phosphates. 

Sodium  and  potassium. 

Calcium  and  magnesium. 

Carbonates. 

Iron. 

Fluorides. 

Nitrates. 

Silicates. 

Hydrogen  peroxide. 

Normal  urine  varies  widely  in  composition,  being  influenced  by  diet 
and  other  factors.  The  following  table  represents  the  composition  of  a 
normal  urine.1 

1  Vierordt:  Daten  und  Tabellen.    Jena,  1906,  p.  330. 


388 


PHYSIOLOGICAL   CHEMISTRY 


COMPOSITION  OF  A  NORMAL  URINE1 
Volume  (24  hours)  1500  c.c. 


Constituent 

Absolute 
weight, 
grams 

Approximate 
percentage 

1 

Water  

14.40  .  oo 

06  o 

Solids  

60.0 

A     O 

Urea  

7C.O 

2    33 

Uric  acid  

O.7"? 

O   CX 

Hippuric  acid 

O    7 

o  05 

Oxalic  acid 

O   OI? 

O   OOI 

Aromatic  oxyacids 

o  06 

O   OOd. 

Creatinine                                                             

I    O 

O   O7 

Thiocyanic  acid  (as  KSCN)                            

o  ic 

O   OI 

Indican          .                                                      

O   OI 

O   OOI 

Ammonia                                                                

o  6< 

O   O4. 

Sodium  chloride                                                  

16  <; 

I    I 

Phosphoric  acid  

2.S 

o.  i«; 

Total  sulphuric  acid2  

2-5 

o.  15 

Silicic  acid  

O.4? 

O.O3 

Potassium  (K20)  

2.  S 

0.15 

Sodium  (Na2O)                                                 

^    O 

O    3 

Calcium  (CaO)  

0.25 

0.015 

Magnesium  (MgO)  

0.30 

O.O2 

Iron.                                                           

O.OO1? 

O.OOO4 

1  The  values  in  this  table  were  obtained  from  the  analysis  of  a  single  specimen  of  urine 
and  are  not  to  be  confused  with  normal  averages  which  are  based  on  the  analysis  of  many 
normal  urines. 

2  For  data  as  to  "partition  "  of  sulphur  and  nitrogen,  see  Chapter  XXVIII  on  Metabolism . 


URINE 

NH2 


389 


UREA,     C  =  0. 

I 
NH2 

Urea  is  the  principal  end-product  of  the  metabolism  of  protein 
substances.  It  was  formerly  believed  that  about  90  per  cent  of  the 
total  nitrogen  of  the  urine  was  present  as  urea.  Folin,  however,  has 
shown  that  the  distribution  of  the  nitrogen  of  the  urine  among  urea 
and  the  other  nitrogen-containing  bodies  present  depends  entirely 
upon  the  absolute  amount  of  the  total  nitrogen  excreted.  He  found 
that  a  decrease  in  the  total  nitrogen  excretion  was  always  accom- 
panied by  a  decrease  in  the  percentage  of  the  total  nitrogen  excreted 
as  urea,  and  that  after  so  regulating  the  diet  of  a  normal  person  as  to 


FIG.  123. — UREA. 

cause  the  excretion  of  total  nitrogen  to  be  reduced  to  3-4  grams  in  24 
hours,  only  about  60  per  cent  of  this  nitrogen  appeared  in  the  urine  as  urea. 
His  experiments  also  seem  to  show  urea  to  be  the  only  one  of  the  nitroge- 
nous excretions  which  is  relatively  as  well  as  absolutely  decreased  as  a 
result  of  decreasing  the  amount  of  protein  metabolized.  This  same 
investigator  reports  a  hospital  case  in  which  only  14.7  per  cent  of  the 
total  nitrogen  was  present  as  urea  and  about  40  per  cent  was  present  as 
ammonia.  Morner  had  previously  reported  a  case  in  which  but  4.4 
per  cent  of  the  total  nitrogen  of  the  urine  was  present  as  urea,  and  26.7 
per  cent  was  present  as  ammonia. 

Urea  occurs  most  abundantly  in  the  urine  of  man  and  carnivora 
and  in  somewhat  smaller  amount  in  the  urine  of  herbivora;  the  urine 
of  fishes,  amphibians,  and  certain  birds  also  contains  a  small  amount  of 


39°  PHYSIOLOGICAL  CHEMISTRY 

the  substance.  Urea  is  also  found  in  nearly  all  the  fluids  and  in  many 
of  the  tissues  and  organs  of  mammals.  The  amount  excreted,  under 
normal  conditions,  by  an  adult  man  in  24  hours  is  about  30-35  grams. 
The  excretion  is  greatest  in  amount  after  a  diet  of  meat,  and  least  in 
amount  after  a  diet  consisting  of  non-nitrogenous  foods;  this  is  due  to  the 
fact  that  the  urea  output  is  regulated  by  the  protein  ingestion.  It  is 
true  also  that  a  non-nitrogenous  diet  has  a  tendency  to  decrease  the 
metabolism  of  the  tissue  proteins  and  thus  cause  the  output  of  urea  under 
these  conditions  to  fall  below  the  output  of  urea  observed  during  starva- 
tion. The  output  of  urea  is  also  increased  after  copious  water-  or  beer- 
drinking.  The  increase  is  probably  due  primarily  to  the  washing  out  of 
the  tissues  of  the  urea  previously  formed,  but  which  had  not  been  re- 
moved in  the  normal  processes,  and  secondarily  to  a  stimulation  of 
protein  catabolism. 

Urea  may  be  formed  in  the  organism  from  amino-acids  such  as  leu- 
cine,  glycocoll,  and  aspartic  acid:  it  may  also  be  formed  from  ammonium 
carbonate  (NH^COs  or  ammonium  carbamate,  H4N.O.CO.NH2. 

There  are  differences  of  opinion  regarding  the  transformation  of  the 
substances  just  named  into  urea,  but  there  is  rather  conclusive  evidence 
that  at  least  a  part  of  the  urea  is  formed  in  the  liver;  it  may  be  formed  in 
other  organs  or  tissues  as  well. 

Urea  crystallizes  in  long,  colorless,  four-  or  six-sided,  anhydrous, 
rhombic  prisms  (Fig.  123),  which  melt  at  i32°C.  and  are  soluble  in 
water  or  alcohol  and  insoluble  in  ether  or  chloroform.  If  a  crystal  of 
urea  is  heated  in  a  test-tube,  it  melts  and  decomposes  with  the  liberation 
of  ammonia.  The  residue  contains  cyanuric  acid, 

C.OH 

N    N 

II       I 
HO.C     C.OH 

V 

N 


NH2 

I 
and  biuret,  C  =  0 

NH 


NH 


URINE 


391 


The  biuret  may  be  dissolved  in  water  and  a  reddish-violet  color  obtained 
by  treating  the  aqueous  solution  with  copper  sulphate  and  potassium 
hydroxide  (see  Biuret  Test,  page  99).  Certain  hypochlorites  or  hypo- 
bromites  in  alkaline  solution  have  the  power  of  decomposing  urea  into 
nitrogen,  carbon  dioxide,  and  water.  Sodium  hypobromite  brings 
about  this  decomposition,  as  follows: 

CO(NH2)2+3NaOBr->3NaBr+N2+C02+2H2O. 
This  property  forms  the  basis  for  a  clinical  quantitative  determination 
of  urea  which  was  formerly  in  use,  but  which  has  been  discarded  because 
of  inaccuracies. 

The  soy  bean  and  jack  bean  have  been  shown  to  contain  an  enzyme 
called  urease  which  has  the  power  to  decompose  urea  with  the  liberation 
of  ammonia.1  This  fact  is  made  use  of  in  the  quantitative  determina- 
tion of  urea  (see  Chapter  XXVII). 


FIG.  124. — UREA  NITRATE. 

Urea  has  the  power  of  forming  crystalline  compounds  with  certain 
acids;  urea  nitrate  and  urea  oxalate  are  the  most  important  of  these 
compounds.  Urea  nitrate,  CO(NH2)2.HN08,  crystallizes  in  colorless, 
rhombic  or  six-sided  tiles  (Fig.  124,  above),  which  are  easily  soluble  in 
water.  Urea  oxalate,  [CO(NH2)2]2.H2C204,  crystallizes  in  the  form 
of  rhombic  or  six-sided  prisms  or  plates  (Fig.  126,  page  393):  the 
oxalate  differs  from  the  nitrate  in  being  somewhat  less  soluble  in 
water.  The  formation  of  the  nitrate  and  oxalate  and  the  decomposition 
of  urea  by  the  enzyme  urease  are  the  most  satisfactory  methods  for  the 
detection  of  urea. 

A  decrease  in  the  excretion  of  urea  is  observed  in  many  diseases  in 
which  the  diet  is  much  reduced  and  in  some  disorders  as  a  result  of 
1  Takeuchi:  Jour.  College  of  Agr.,  Tokyo,  1909,  Part  I. 


3Q2  PHYSIOLOGICAL    CHEMISTRY 

alterations  in  metabolism,  e.g.,  myxedema,  and  in  others  as  a  result 
of  changes  in  excretion,  as  in  severe  and  advanced  kidney  disease.  A 
pathological  increase  is  found  in  a  large  proportion  of  diseases  which 
are  associated  with  a  toxic  state.  In  marked  acidosis  it  may  be  con- 
siderably decreased  relative  to  the  total  nitrogen  (see  Ammonia) . 

EXPERIMENTS  ON  UREA 

i.  Isolation  from  the  Urine.1— Place  800  c.c.  of  urine  in  a  precipitating  jar, 
add  250  c.c.  of  baryta  mixture,2  and  stir  thoroughly.  Filter  off  the  precipitate 
of  phosphates,  sulphates,  urates,  and  hippurates  and 
evaporate  the  filtrate  on  a  water-bath  to  a  thick  syrup. 
This  syrup  contains  chlorides,  creatinine,  organic  salts, 
pigments,  and  urea.  Extract  the  syrup  with  warm  95 
per  cent  alcohol  and  filter  again.  The  filtrate  con- 
tains the  urea  contaminated  with  pigment.  Decolor- 
ize the  filtrate  by  boiling  with  animal  charcoal,  filter 
again,  and  stand  the  filtrate  away  in  a  cold  place  for 
crystallization.  Examine  the  crystals  under  the  micro- 
scope and  compare  them  with  those  shown  hi  Fig.  123, 
page  400. 

2.  Solubility. — Test  the  solubility  of  urea,  prepared 
by  yourself  or  furnished  by  the  instructor,  in  water  and 
in  alcohol  and  ether. 

3.  Melting-point. — Determine  the  melting-point  of 
some  pure  urea  furnished  by  the  instructor.     Proceed 
as  follows:  Into  an  ordinary  melting-point  tube,  sealed 
at  one  end,  introduce  powdered  urea.     Fasten  the  tube 
to  the  bulb  of  a  thermometer  as  shown  in  Fig.  125,  and 
suspend  the  bulb  and  its, attached  tube  in  a  small  beaker 
containing  sulphuric  acid.     Gently  raise  the  tempera- 
ture of  the  acid  by  means  of  a  low  flame,  stirring  the 
fluid  continually,  and  note  the  temperature  at  which 
the  urea  begins  to  melt. 

FIG.  ^-MELTING-  4-  Crystalline  Form.— Dissolve  a  crystal  of  pure 
POINT  TUBES  FASTENED  urea  in  a  few  drops  of  95  per  cent  alcohol  and  place 
TO  BULB  or  THERMOM-  !_2  drops  of  the  alcoholic  solution  on  a  microscopic 
slide.  Allow  the  alcohol  to  evaporate  spontaneously, 

examine  the  crystals  under  the  microscope,  and  compare  them  with  those  re- 
produced in  Fig.  123,  page.  389.  Recrystallize  a  little  urea  from  water  in  the 
same  way  and  compare  the  crystals  with  those  obtained  from  the  alcoholic 
solution. 

5.  Formation  of  Biuret. — Place  a  small  amount  of  urea  hi  a  dry  test-tube 
and  heat  carefully  in  a  low  flame.  The  urea  melts  at  i32°C.  and  liberates 
ammonia.  Continue  heating  until  the  fused  mass  begins  to  solidify.  Cool  the 

1  The  method  based  upon  the  precipitation  by  nitric  acid  is  also  satisfactory  (see 
Hoppe-Seyler's  Handbuch  der  Physiol.  undPathol.  Chem.  Anal.,  Eighth  edition,  1909,  p.  145). 

2  Baryta  mixture  consists  of  a  mixture  of  i  volume  of  a  saturated  solution  of  Ba(NOs)2 
and  2  volumes  of  a  saturated  solution  of  Ba(OH)2. 


URIN£  393 

tube,  dissolve  the  residue  in  dilute  potassium  hydroxide  solution,  and  add  very 
dilute  copper  sulphate  solution  (see  page  99).  The  purplish-violet  color  is  due 
to  the  presence  of  biuret  which  has  been  formed  from  the  urea  through  the 
application  of  heat  as  indicated.  This  is  the  reaction  : 

NH2 
/  NH2 

Urea.    C  =  0 

\  c=o 

NH2i  \ 

EM  NH+NH3 


H  C=0 

Urea.  C  =  O 

I  NH2 

NH2  Biuret- 

6.  Urea  Nitrate.  —  Prepare  a  concentrated  solution  of  urea  by  dissolving 
a  little  of  the  substance  in  a  few  drops  of  water.  Place  a  drop  of  this  solution  on  a 
microscopic  slide,  add  a  drop  of  concentrated  nitric  acid,  and  examine  under  the 
microscope.  Compare  the  crystals  with  those  reproduced  in  Fig.  124,  page  391. 


FIG.  126. — UREA  OXALATE. 

7.  Urea  Oxalate. — To  a  drop  of  a  concentrated  solution  of  urea,  prepared  as 
described  in  the  last  experiment  (6),  add  a  drop  of  a  saturated  solution  of  oxalic 
acid.    Examine  under  the  microscope  and  compare  the  crystals  with  those  shown 
in  Fig.  126,  above. 

8.  Decomposition  by  Urease.— To  5  c.c.  of  urea  solution  in  a  test  tube  add 
i  c.c.  of  urease  solution  or  a  little  soy  bean  or  jack  bean  powder.    Allow  the 
tube  to  stand  for  ten  minutes,  heat  the  contents  to  boiling,  holding  moist  red 
and  blue  litmus  papers  at  the  mouth  of  the  tube.    What  do  you  observe? 
Note  the  odor.    Explain. 

9*  Decomposition  by  Sodium  Hypobromite. — Into  a  mixture  of  3  c.c.  of  con- 
centrated sodium  hydroxide  solution  and  2  c.c.  of  bromine  water  in  a  test-tube 


394  PHYSIOLOGICAL  CHEMISTRY 

introduce  a  crystal  of  urea  or  a  small  amount  of  concentrated  solution  of  urea. 
Through  the  influence  of  the  sodium  hypobromite,  NaOBr,  the  urea  is  decom- 
posed and  carbon  dioxide  and  nitrogen  are  liberated.  The  carbon  dioxide  is 
absorbed  by  the  excess  of  sodium  hydroxide,  while  the  nitrogen  is  evolved  and 
causes  the  marked  effervescence  observed.  This  property  forms  the  basis  for 
one  of  the  methods  in  common  use  for  the  quantitative  determination  of  urea. 
Write  the  equation  showing  the  decomposition  of  urea  by  sodium  hypobromite. 
It  is  claimed  that  all  ammonium  compounds  and  all  compounds 
containing  the  amino  (  —  NH2)  group  yield  nitrogen  when  treated  with 
hypobromite  as  in  this  test. 

HN—  CO 

I       I 

URIC  ACID,  OC      C-NH 


HN—  C—  NH 

Uric  acid  is  one  of  the  most  important  of  the  constituents  of  the 
urine.  It  is  generally  stated  that  normally  about  0.7  gram  is  excreted 
in  24  hours,  but  that  this  amount  is  subject  to  wide  variations,  particu- 
larly under  certain  dietary  and  pathological  conditions.  It  has  been 
shown,  however,  that  the  average  daily  excretion  of  uric  acid  for  ten 
men  ranging  in  age  from  19  to  29  years  and  fed  a  normal  mixed  diet 
was  0.597  gram>  a  value  somewhat  lower  than  the  generally  accepted 
average  of  0.7  gram  for  such  a  period.  On  a  purine-free  diet  the  uric 
acid  output  maybe  0.1-0.5  gram  per  day,  whereas  a  high  purine  diet  may 
yield  a  daily  output  of  2  grams.  Uric  acid  is  a  diureide  and  consequently 
upon  oxidation  may  yield  two  molecules  of  urea.  It  acts  as  a  weak  di- 
basic acid  and  forms  two  classes  of  salts,  neutral  and  acid.  The  neutral 
potassium  and  lithium  urates  are  the  most  easily  soluble  of  the  alkali 
salts;  the  ammonium  urate  is  difficultly  soluble.  The  acid-alkali  urates 
are  more  insoluble  and  form  the  major  portion  of  the  sediment  which 
separates  upon  cooling  the  concentrated  urine;  the  alkaline  earth  urates 
are  very  insoluble.  Ordinarily  uric  acid  occurs  in  the  urine  in  the  form 
of  urates  and  upon  acidifying  the  liquid  the  uric  acid  is  liberated  and 
deposits  in  crystalline  form.  This  property  forms  the  basis  of  one  of 
the  older  methods  for  the  quantitative  determination  of  uric  acid 
(Heintz  Method.) 

Uric  acid  is  very  closely  related  to  the  purine  bases  as  may  be  seen 
from  a  comparison  of  its  structural  formula  with  those  of  the  purine 
bases  given  on  page  126.  According  to  the  purine  nomenclature  it  is 
designated  2-6-8-  trioxypurine.  Uric  acid  forms  the  principal  end- 
product  of  the  nitrogenous  metabolism  of  birds  and  scaly  reptiles; 
in  the  human  organism  it  occupies  the  fourth  position  inasmuch  as  here 


URINE 


395 


urea,  ammonia,  and  creatinine  are  the  chief  end-products  of  nitrogen- 
ous metabolism.  It  is  generally  said  that  the  relation  existing  between 
uric  acid  and  urea  in  human  urine  under  normal  conditions  varies  on 
the  average  from  1 140  to  i :  100  and  is  subject  to  wider  variations  under 
pathological  conditions;  and  further  that  because  of  the  high  content  of 
uric  acid  in  the  urine  of  newborn  infants  the  ratio  may  be  increased  to 
i  MO  or  even  higher.  We  now  know  that  this  ratio  of  uric  acid  to  urea 
is  of  little  significance  under  any  conditions. 

In  man,  uric  acid  probably  results  principally  from  the  destruction 
of  nuclein  material.  It  may  arise  from  nuclein  or  other  purine  material 
ingested  as  food  or  from  the  disintegrating  cellular  matter  of  the  organ- 
ism. The  uric  acid  resulting  from  the  first  process  is  said  to  be  of  ex- 
ogenous origin,  whereas  the  product  of  the  second  form  of  activity  is 
said  to  be  of  endogenous  origin.  As  a  result  of  experimentation,  Siven, 
and  Burian  and  Schur,  and  Rockwood  claim  that  the  amount  of  endoge- 
nous uric  acid  formed  in  any  given  period  is  fairly  constant  for  each 
individual  under  normal  conditions,  and  that  it  is  entirely  independent 
of  the  total  amount  of  nitrogen  eliminated.  Folin  has  taken  exception 
to  the  statements  of  these  investigators  and  claims  that,  following  a 
pronounced  decrease  in  the  amount  of  protein  metabolized,  the  absolute 
quantity  of  uric  acid  is  decreased  but  that  this  decrease  is  relatively 
smaller  than  the  decrease  in  the  total  nitrogen  excretion  and  that  the 
per  cent  of  the  uric  acid  nitrogen,  in  terms  of  the  total  nitrogen,  is  there- 
fore decidedly  increased.  According  to  Mares',1  food-stuffs  act  to  in- 
crease the  endogenous  uric  acid  output  6y  stimulating  the  digestive 
glands  to  activity.  That  a  portion  of  the  endogenous  uric  acid  may 
arise  in  this  way  has  recently  been  shown  by  Mendel  and  Stehle.2 

In  birds  the  formation  of  uric  acid  is  analogous  to  the  formation 
of  urea  in  man.  In  these  organisms  it  is  derived  principally  from  the 
protein  material  of  the  tissues  and  the  food  and  is  formed  through  a 
process  of  synthesis  which  occurs  for  the  most  part  in  the  liver;  a 
comparatively  small  fraction  of  the  total  uric  acid  excretion  of  birds 
may  result  from  nuclein  material. 

When  pure,  uric  acid  may  be  obtained  as  a  white,  odorless,  and 
tasteless  powder,  which  is  composed  principally  of  small,  transparent, 
crystalline,  rhombic  plates.  Uric  acid  as  it  separates  from  the  urine 
is  invariably  pigmented,  and  crystallizes  in  a  large  variety  of  character- 
istic forms,  e.g.,  dumb-bells,  wedges,  rhombic  prisms,  irregular  rec- 
tangular or  hexagonal  plates,  whetstones,  prismatic  rosettes,  etc.  Uric 
acid  is  insoluble  in  alcohol  and  ether,  soluble  with  difficulty  in  boiling 

\  JJare^:  Arch  f .d  ges.  Physiol.,  134,  59,  1910. 

*  Mendel  and  Stehle:  Jour.  Biol.  Chem.,  22,  215,  1915. 


3  96  PHYSIOLOGICAL  CHEMISTRY 

water  (i  :  1800)  and  practically  insoluble  in  cold  water  (i  :  39,480,  at 
i8°C.).  It  is  soluble  in  alkalis,  alkali  carbonates,  boiling  glycerol, 
concentrated  sulphuric  acid,  and  in  certain  organic  bases  such  as  ethyl- 
amine  and  piperidine.  It  is  claimed  that  the  uric  acid  is  held  in  solu- 
tion in  the  urine  by  the  urea  and  disodium  hydrogen  phosphate  present. 
Uric  acid  possesses  the  power  of  reducing  cupric  hydroxide  in  alkaline 
solution  and  may  thus  lead  to  an  erroneous  conclusion  in  testing  for 
sugar  in  the  urine  by  means  of  Fehling's  or  Trommer's  test.  A  white 
precipitate  of  cuprous  urate  is  formed  if  only  a  small  amount  of  cupric 
hydroxide  is  present,  but  if  enough  of  the  copper  salt  is  present  the 
characteristic  red  or  brownish-red  precipitate  of  cuprous  oxide  is  ob- 
tained. Uric  acid  does  not  possess  the  power  of  reducing  bismuth  in 
alkaline  solution  and  therefore  does  not  interfere  in  testing  for  sugar  in 
the  urine  by  means  of  Boettger's  or  Nylander's  tests. 

In  addition  to  being  an  important  urinary  constituent  uric  acid 
is  present  in  small  amounts  in  normal  human  blood  as  well  as  in  the 
blood  of  birds.  It  is  also  normally  present  in  the  brain,  heart,  liver, 
lungs,  pancreas,  and  spleen. 

Pathologically,  the  excretion  of  uric  acid  is  subject  to  wide  varia- 
tions, but  the  experimental  findings  are  rather  contradictory.  It  may  be 
stated  with  certainty,  however,  that  in  leukemia,  because  of  the  destruc- 
tion of  nuclein  material,  the  uric  acid  output  is  increased  absolutely  as 
well  as  relatively  to  the  urea  output;  under  these  conditions  the  ratio 
between  the  uric  acid  and  urea  may  be  as  low  as  i :  9,  whereas  the  normal 
ratio,  as  we  have  seen,  is  i :  50  or  higher.  An  actual  output  of  12  grams 
of  uric  acid  per  day  has  been  reported  in  leukemia.  In  the  study  of  the 
influence  of  X-ray  on  metabolism  Edsall  and  others  have  reached  some 
interesting  conclusions.  Edsall  found  that  the  excretion  of  uric  acid  is 
usually  increased  and  that  in  some  conditions,  particularly  in  leukemia, 
it  may  be  greatly  increased.  The  excretion  of  total  nitrogen,  phos- 
phates, and  other  sustances  may  also  be  considerably  increased. 

In  gout  the  kidney  is  said  to  lose  the  power  of  properly  eliminating 
uric  acid  and  it  collects  in  the  blood  in  abnormally  high  concentration. 

Normal  =  2-3  mg.  uric  acid  per  100  grams  of  blood. 
Gout  =  4-10  mg.  uric  acid  per  100  grams  of  blood. 

In  gout  the  uric  acid  content  of  the  urine  is  generally  low  preceding 
an  attack  and«  increases  during  the  attack.  Atophan  has  been  found 
to  increase  the  uric  acid  output  in  gout,  apparently  due  to  increased 
kidney  activity. 

The  uric  acid  conterit  of  the  urine  is  of  importance  in  relation  to  the 
formation  of  urjc  acid  calculi.  The  administration  of  alkali  carbonates 


PLATE  V. 


URIC  ACID  CRYSTALS.    NORMAL  COLOR.     (From  Purdy,  after  Peyer.) 


URINE 


397 


and  citrates,  or  the  feeding  of  base-forming  foods,  by  decreasing  the 
acidity  of  the  urine  increases  its  solvent  power  for  uric  acid  and  de- 
creases the  liability  of  formation  of  this  type  of  calculus.1 


EXPERIMENTS  ON  URIC  ACID 

1.  Isolation  from  the  Urine. — Place  about  200  c.c.  of  filtered  urine  in  a 
beaker,  render  it  acid  with  2-10  c.c.  of  concentrated  hydrochloric  acid,  stir 
thoroughly,  and  stand  the  vessel  hi  a  cold  place  for  24  hours.    Examine  the  pig- 
mented  crystals  of  uric  acid  under  the  microscope  and  compare  them  with  those 
shown  hi  Fig.  142,  page  478,  and  PL  V,  opposite. 

2.  Solubility. — Try  the  solubility  of  pure  uric  acid,  furnished  by  the  in- 
structor, hi  water,  dilute  acid  and  alkali  and  in  alcohol,  ether  and  concentrated 
sulphuric  acid. 

3.  Crystalline  Form  of  Pure  Uric  Acid. — Place  about  100  c.c.  of  water  hi  a 
small  beaker,  render  it  distinctly  alkaline  with  potassium  hydroxide  solution  and 


FIG.  127. — PURE  URIC  ACID. 

add  a  small  amount  of  pure  uric  acid,  stirring  continuously.  Cool  the  solution , 
render  it  distinctly  acid  with  hydrochloric  acid  and  allow  it  to  stand  hi  a  cool 
place  for  crystallization.  Examine  the  crystals  under  the  microscope  and  com- 
pare them  with  those  reproduced  hi  Fig.  127. 

4.  Murexide  Test. — To  a  small  amount  of  pure  uric  acid  in  a  small  evaporating 
dish  add  2-3  drops  of  concentrated  nitric  acid.  Evaporate  to  dryness  carefully 
on  a  water-bath  or  over  a  very  low  flame.  A  red  or  yellow  residue  remains  which 
turns  purplish  red  after  cooling  the  dish  and  adding  a  drop  of  very  dilute  am- 
monium hydroxide.  The  color  is  due  to  the  formation  of  murexide.  If  potas- 
sium hydroxide  is  used  instead  of  ammonium  hydroxide  a  purplish  violet  color 
due  to  the  production  of  the  potassium  salt  is  obtained.  The  color  disappears 
upon  warming ;  with  certain  related  bodies  (purine  bases)  the  color  persists  under 
these  conditions. 

1  Blather  wick:  Arch.  Int.  Med.,  14,  409,  1914. 


398  PHYSIOLOGICAL   CHEMISTRY 

In  this  reaction  the  uric  acid  is  oxidized  to  dialuric  acid  and  alloxan. 
These  two  substances  condense  to  form  alloxan  tin.  This  alloxantin 
reacts  with  ammonium  hydroxide  to  form  purpuric  acid.  The  purple 
color  is  due  to  the  formation  of  ammonium  pur  pur  ate  or  murexide. 

5.  Phosphotungstic  Acid  Reaction  (Folin). — To  20  c.c.  of  saturated  sodium 
carbonate  solution  in  a  small  beaker  add  a  small  amount  of  uric  acid.  ,  Stir 
the  solution  until  the  uric  acid  has  dissolved,  then  add  i  c.c.  of  Folin's  uric 
acid  reagent  (see  Chapter  XXVII).    A  blue  color  results. 

6.  Silver  Reduction  Test  (Schiff). — Dissolve  a  small  amount  of  pure  uric  acid 
in  sodium  carbonate  solution  and  transfer  a  drop  of  the  resulting  mixture  to  a 
strip  of  filter  paper  saturated  with  silver  nitrate  solution.    A  yellowish-brown 
or  black  coloration  due  to  the  formation  of  reduced  silver  is  produced. 

It  is  claimed  that  chlorides  interfere  with  this  test. 

7.  Ganassini's  Test.1 — Dissolve  a  small  amount  of  uric  acid  in  sodium  carbon- 
ate.   Precipitate  the  dissolved  uric  acid  by  means  of  zinc  chloride,  filter  off  the 
precipitate,  and  permit  it  to  stand  in  contact  with  the  air.    A  sky-blue  color  will 
develop,  a  color  change  which  may  be  hastened  by  sunlight.    A  similar  reaction 
may  be  obtained  by  treating  the  original  precipitate  with  K2S208. 

8.  Influence  upon  Fehling's  Solution. — Dilute  i  c.c.  of  Fehling's  solution 
with  4  c.c.  of  water  and  heat  to  boiling.    Now  add  slowly,  a. few  drops  at  a 
time,  1-2  c.c.  of  a  concentrated  solution  of  uric  acid  in  potassium  hydroxide, 
heating  after  each  addition.    From  this  experiment  what  do  you  conclude  re- 
garding the  possibility  of  arriving  at  an  erroneous  decision  when  testing  for  sugar 
in  the  urine  by  means  of  Fehling's  test  ? 

9.  Reduction  of  Nylander's  Reagent. — To  5  c.c.  of  a  solution  of  uric  acid 
in  potassium  hydroxide  add  about  one-half  a  cubic  centimeter  of  Nylander's 
reagent  and  heat  to  boiling  for  a  few  moments.    Do  you  obtain  the  typical  black 
end-reaction  signifying  the  reduction  of  the  bismuth? 

NH CO 

CREATININE,     C  =  NH 

N(CH3).C] 

Creatinine  is  the  anhydride  of  creatine  and  is  a  constituent  of  normal 
human  urine.  The  theory  that  creatinine  is  derived  from  the  creatine 
of  ingested  muscular  tissue  as  well  as  from  the  creatine  of  the  muscular 
tissue  of  the  organism  has  been  proven  to  be  incorrect  by  Folin, 
Klercker,  and  Wolf  and  Shaffer.  Shaffer  believes  that  creatinine  is 
the  result  of  some  special  process  of  normal  metabolism  which  takes 
place  to  a  large  extent,  if  not  entirely,  in  the  muscles,  and  further  that 
the  amount  of  such  creatinine  elimination,  expressed  in  milligrams  per 
kilogram  body  weight,  is  an  index  of  this  special  process.2  He  further 

1  Ganassini:  Boll,  soc.,  1908,  No.  i. 

2  He  proposes  to  designate  as  the  "creatinine  coefficient"  the  excretion  of  creatinine- 
nitrogen  (mg.}  per  kilogram  of  body  weight. 


URINE  399 

states  that  the  muscular  efficiency  of  the  individual  depends  upon  the 
intensity  of  this  process.  Under  normal  conditions  about  1-1.25  grams 
of  creatinine  is  excreted  by  an  adult  man  in  24  hours,1  the  exact  amount 
depending  in  great  part  upon  the  nature  of  the  food  and  decreasing 
markedly  in  starvation.  Very  little  that  is  important  is  known  re- 
garding the  excretion  of  creatinine  under  pathological  conditions.  The 
creatinine  content  of  the  urine  is  said  to  be  increased  in  typhoid  fever, 
typhus,  tetanus,  and  pneumonia,  and  to  be  decreased  in  anaemia,  chloro- 
sis, paralysis,  muscular  atrophy,  advanced  degeneration  of  the  kidneys, 
and  in  leukemia  (myelogeneous,  lymphatic  and  pseudo).  An  increase 


FIG.  128. — CREATININE. 

of  creatinine  was  also  noted  in  diabetes,  an  increase  probably  due  to  the 
creatinine  content  of  the  meat  eaten.  The  greater  part  of  the  data, 
however,  relating  to  the  variation  of  the  creatinine  excretion  under 
pathological  conditions  are  not  of  much  value  since  in  nearly  every 
instance  the  diet  was  not  sufficiently  controlled  to  permit  the  collection 
of  reliable  data.  And  further,  until  the  advent  of  the  Folin  method 
(see  page  526)  there  was  no  \accurate  method  for  the  quantitative 
determination  of  creatinine.  Shaffer  has  called  attention  to  the  fact 
that  a  low  excretion  of  creatinine  is  found  in  the  urine  of  a  remarkably 
large  number  of  pathological  subjects,  representing  a  variety  of  con- 
ditions, and  that  it  is  therefore  evident  that  the  excretion  of  an  ab- 
normally small  amount  of  this  substance  is  by  no  means  peculiar  to  any 
one  disease.  A  considerable  increase  in  the  creatinine  content  of  the 
blood  has  been  observed  in  uremia.2 

1  According  to  Shaffer  the  amount  excreted  by  strictly  normal  individuals  is  between  7 
and  1 1  mg.  of  creatinine-nitrogen  per  kilogram  of  body  weight. 
1  Folin  and  Denis:  Jour.  Biol.  Chem.,  17,  487,  1914. 
Myers  and  Fine:  Jour.  Biol.  Chem.,  20,  391,  1914. 


400  PHYSIOLOGICAL  CHEMISTRY 

.  Creatinine  crystallizes  in  colorless,  glistening  monoclinic  prisms  (Fig. 
128,  page  399)  which  are  soluble  in  about  12  parts  of  cold  water;  they 
are  more  soluble  in  warm  water  and  in  warm  alcohol.  It  forms  salts  only 
with  strong  mineral  acids.  One  of  the  most  important  and  interesting 
of  the  compounds  of  creatinine  is  creatinine-zinc  chloride,  (C4H7N3O)2- 
ZnCt,  which  is  formed,  from  an  alcoholic  solution  of  creatinine  upon 
treatment  with  zinc  chloride  in  acid  solution.  Creatinine  has  the  power 
of  reducing  cupric  hydroxide  in  alkaline  solution  and  in  this  way  may 
interfere  with  the  determination  of  sugar  in  the  urine.  In  the  reduction 
by  creatinine  the  blue  liquid  is  first  changed  to  a  yellow,  and  the  forma- 
tion of  a  brownish-red  precipitate  of  cuprous  oxide  is  brought  about  only 
after  continuous  boiling  with  an  excess  of  the  copper  salt.  Creatinine 
does  not  reduce  alkaline  bismuth  solutions  and  therefore  does  not  inter- 
fere with  Nylander's  and  Boettger's  tests. 

It  has  recently  been  shown  by  Folin  that  the  absolute  quantity  of 
creatinine  eliminated  in  the  urine  on  a  meat-free  diet  is  a  constant 
quantity  different  for  different  individuals,  but  wholly  independent  of 
quantitative  changes  in  the  total  amount  of  nitrogen  eliminated. 
Shaffer  has  very  recently  confirmed  these  findings  and  has  shown  that 
the  output  of  creatinine  under  these  conditions  is  constant  from  hour 
to  hour  as  well  as  from  day  to  day. 

EXPERIMENTS  ON  CREATININE 

i.  Preparation  of  Pure  Creatinine  from  Urine  (Folin-Benedict1). — To  10 
liters2  of  undecomposed  urine  in  a  large  precipitating  jar  add  with  stirring  a  hot 
solution  of  1 80  grams  of  picric  acid  in  450  c.c.  of  boiling  alcohol.  Allow  to  stand 
over  night  and  syphon  off  the  supernatant  fluid.  Pour  the  residue  upon  a  large 
Buchner  funnel,  drain  with  suction,  wash  once  or  twice  with  cold  saturated  picric 
acid  and  suck  dry.  Treat  the  dry  or  nearly  dry  picrate  in  a  large  mortar  or  evap- 
.  orating  dish  with  enough  concentrated  HC1  to  form  a  moderately  thin  paste  (about 
60  c.c.  of  acid  for  each  100  grams  of  picrate)  and  stir  the  mixture  thoroughly  with 
the  pestle  for  3-5  minutes.  Filter  with  suction  on  a  hardened  paper,  and  wash 
the  residue  twice  with  enough  water  to  cover  it,  sucking  as  nearly  dry  as  possible 
each  time.  Transfer  the  filtrate  to  a  large  flask  and  neutralize  with  an  excess  of 
solid  magnesium  oxide  (the  "heavy"  variety  is  best).  Add  this  oxide  in  small 
portions  with  cooling  of  the  flask  under  running  water  between  the  additions. 
Neutralization  of  the  acid  will  be  indicated  by  a  bright  yellow  color  of  the  mix- 
ture, or  litmus  paper  may  be  used  to  test  it.  Filter  with  suction.  Wash  the 
residue  twice  with  water.  Immediately  add  a  few  cubic  centimeters  of  glacial 
acetic  acid  4o  the  filtrate  to  make  it  strongly  acid.  Pay  no  attention  to  any 
precipitate  that  may  form,  but  dilute  the  solution  with  about  4  volumes  of  95  per 

1  Benedict:  Jour.  Biol.  Chem.,  18,  182,  1914. 

Folin:  Ibid.,  17,  463,  1914. 

8  If  it  is  simply  desired  to  demonstrate  the  presence  of  creatinine,  i  liter  may  be  em- 
ployed and  the  various  reagents  reduced  accordingly. 


URINE  401 

cent  alcohol.  After  15  minutes  filter  off  the  slight  precipitate  which  forms. 
Treat  the  final  filtrate  with  30-40  c.c.  of  30  per  cent  zinc  chloride.  Stir  and  let 
stand  over  night  hi  a  cool  place.  Pour  off  the  supernatant  liquid  and  collect  the 
creatinine  zinc  chloride  on  a  Buchner  funnel,  wash  once  with  water,  then  thor- 
oughly with  50  per  cent  alcohol,  finally  with  95  per  cent  alcohol  and  dry.  A 
nearly  white,  light  crystalline  powder  should  be  obtained.  The  yield  should  be 
90-95  per  cent  of  the  original  creatinine  (usually  about  1.5-1.8  grams  of  creatinine 
zinc  chloride  per  liter  of  urine). 

Recrystallize  the  creatinine  -zinc  chloride  by  treating  10  grams  with  100  c.c. 
of  water  and  about  60  c.c.  of  normal  sulphuric  acid,  heating  the  mixture  until  a 
clear  solution  is  obtained.  Add  about  4  grams  of  purified  animal  charcoal,  con- 
tinue boiling  for  about  a  minute,  filter  with  suction  through  a  small  Buchner 
funnel,  pouring  the  filtrate  back  on  the  filter  three  or  four  times  until  it  runs 
through  perfectly  colorless.  Wash  residue  with  hot  water  and  transfer  the  total 
filtrate  to  a  beaker  and  while  hot  treat  with  a  little  strong  zinc  chloride  solution 
(3  c.c.)  and  with  about  7  grams  of  potassium  acetate  dissolved  in  a  little  water. 
After  ten  minutes  dilute  with  an  equal  volume  of  alcohol,  and  allow  to  stand  hi  a 
cold  place  for  some  hours.  Filter  off  the  crystalline  product  and  examine  under 
microscope  (see  Fig.  115).  To  remove  the  small  amount  of  potassium  sulphate 
which  it  contains  stir  up  with  twice  its  weight  of  water,  filter,  wash  with  a  little 
water  and  then  with  alcohol.  The  preparation  should  be  snow  white.  Yield, 
85-90  per  cent. 

Place  the  finely  powdered  recrystallized  creatinine  zinc  chloride  in  a  dry 
flask  and  treat  with  seven  times  its  weight  (by  volume)  of  concentrated  aqueous 
ammonia.  Warm  slightly  and  agitate  gently  until  a  clear  solution  is  obtained, 
care  being  taken  to  drive  off  no  more  ammonia  during  the  warming  than  is 
necessary  to  obtain  a  clear  solution.  Stopper  the  flask,  allow  to  cool,  place  in 
the  ice-box  for  an  hour  or  more.  Pure  creatinine  crystallizes  out.  It  may  be 
recrystallized  from  boiling  alcohol  or  concentrated  ammonia,  but  this  is  usually 
unnecessary.  The  product  is  perfectly  pure  and  can  be  used  as  a  standard  in 
the  quantitative  determination  of  creatine  and  creatinine.  See  chapters  on 
Quantitative  Analysis  of  Urine  and  Blood. 

i.  Preparation  of  Creatine. — Creatine  may  be  prepared  from  creatinine  zinc 
chloride  by  decomposition  with  calcium  hydrate,  the  process  being  one  of  hydroly- 
sis (Benedict). 

One  hundred  grams  of  creatinine  zinc  chloride  are  treated  with  about  700  c.c. 
of  water  in  a  large  casserole  and  the  mixture  heated  to  boiling;  150  grams  of  pure 
powdered  calcium  hydrate  are  then  added,  with  stirring,  and  the  mixture  boiled 
gently  for  20  minutes  (with  occasional  stirring).  The  hot  mixture  is  then  filtered 
with  suction,  .the  residue  being  washed  with  hot  water.  The  filtrate  is  then  treated 
with  hydrogen  sulphide  gas  for  a  few  minutes  and  poured  through  a  folded  filter 
to  remove  the  zinc.  The  filtrate  is  acidified  by  the  addition  of  about  5  c.c.  of  glacial 
acetic  acid  and  boiled  down  rapidly  to  a  volume  of  about  200  c.c.  This  solution 
is  allowed  to  stand  over  night,  preferably  in  a  cool  place.  The  next  day  the  crys- 
tallized creatine  is  filtered  off  with  suction,  washed  with  a  very  little  cold  water, 
and  then  thoroughly  washed  with  alcohol  and  dried.1  This  product  is  then  recrys- 
tallized by  dissolving  in  about  seven  times  its  weight  of  boiling  water  and  allowing 

1  The  filtrate  obtained  at  this  point  should  be  diluted  with  alcohol  and  treated  with  zinc 
chloride  (50  c.c.  of  a  30  per  cent  solution)  for  recovery  of  the  unconverted  creatinine. 
26 


402 


PHYSIOLOGICAL   CHEMISTRY 


the  solution  to  cool  slowly  and  stand  for  some  hours.  This  product  should  be  per- 
fectly pure  creatine.  If  necessary  it  can  be  recrystallized  with  very  little  loss.  The 
crystallized  product  should  be  filtered  off,  washed  with  alcohol  and  ether  and  dried 
in  air  for  about  half  an  hour.  Thus  obtained  the  creatine  contains  water  of  crystal- 
lization which  it  loses  very  readily  upon  exposure  to  air.  To  prepare  creatine  which 
can  be  weighed  with  absolute  exactness  it  is  necessary  to  dehydrate  this  product  by 
heating  for  some  hours  at  about  95°. 

The  yield  in  this  process  is  about  18  grams  of  recrystallized  creatine,  and 
about  55  grams  of  creatinine  zinc  chloride  recovered.  Longer  boiling  with  lime 
does  not  bring  about  a  greater  yield,  as  after  the  20-minute  point  creatine  is  de- 
composed almost  exactly  as  fast  as  it  is  formed. 

Examine  the  crystals  of  creatine  under  the  microscope  and  compare  with  illus- 
tration in  Chapter  XX  on  Muscular  Tissue.  For  other  creatine  tests  see  Chapter 
XX. 


FIG.  129. — CREATININE-ZINC  CHLORIDE.     (Salkowski.) 

3.  Nitro-prusside  Test  (Weyl).— Take  5  c.c.  of  urine  in  a  test-tube,  add  a  few 
drops  of  sodium  nitro-prusside  and  render  the  solution  alkaline  with  potassium 
hydroxide  solution.    A  ruby-red  color  results  which  soon  turns  yellow.    See 
Legal's  test  for  acetone,  page  452. 

4.  Nitro-prusside-acetic  Acid  Test  (Salkowski). — To  the  yellow  solution  ob- 
tained in  Weyl's  test  above  add  an  excess  of  acetic  acid  and  apply  heat.    A  green 
color  results  and  is  in  turn  displaced  by  a  blue  color.    A  precipitate  of  Prussian 
blue  may  form. 

5.  Picric  Acid  Reaction  (Jaffe).— Place  5  c.c.  of  urine  in  a  test-tube,  add  an 
aqueous  solution  of  picric  acid  and  render  the  mixture  alkaline  with  potassium 
hydroxide  solution.    A  red  color  is  produced  which  turns  yellow  if  the  solution  be 
acidified.    Glucose  gives  a  similar  red  color  but  only  upon  the  application  of  heat. 
This  color  reaction  observed  when  creatinine  in  alkaline  solution  is  treated  with 
picric  acid  is  the  basic  principle  of  Folin's  colorimetric  method  for  the  quantitative 
determination  of  creatinine  (see  page  526). 

ETHEREAL  SULPHATES 

The  most  important    of    the    ethereal    sulphates    found    in    the 
urine  are  phenol-sulphuric  acid,  p-cresol-sulphuric  acid,  indoxyl-sulphuric 


URINE  403 

acid,  and  skatoxyl-sulphuric  acid.  Pyrocatechol-sulphuric  acid  also 
occurs  in  traces  in  human  urine.  The  total  output  of  ethereal  sulphuric 
acid  (as  SOs)  varies  ordinarily  from  o.i  gram  to  0.25  gram  for  24  hours 
and  comprises  5-15  per  cent  of  the  total  sulphur.  In  health  the  ratio 
of  ethereal  sulphuric  acid  to  inorganic  sulphuric  acid  is  about  1:10. 
These  ethereal  sulphuric  acids  originate  in  part  from  the  phenol,  cresol, 
indole  and  skatole  formed  in  the  putrefaction  of  protein  material  in 
the  intestine.  The  phenol  passes  to  the  liver  where  part  of  it  is  conju- 
gated to  form  phenol  potassium  sulphate  and  appears  in  this  form  in  the 
urine  whereas  the  indole  and  skatole  undergo  a  preliminary  oxidation  to 
form  indoxyl  and  skatoxyl  respectively  before  their  conjugation  and 
elimination. 

It  was  formerly  generally  considered  that  each  of  the  ethereal  sul- 
phuric acids  was  formed  principally  in  the  putrefaction  of  protein 
material  in  the  intestine  and  that  therefore  a  determination  of  the  total 
ethereal  sulphuric  acid  content  of  the  urine  was  an  index  of  the  extent  to 
which  these  putrefactive  processes  were  proceeding  within  the  organism. 
Folin,  however,  conducted  a  series  of  experiments  which  seemed  to 
show  that  the  ethereal  sulphuric  acid  content  of  the  urine  did  not  afford 
an  index  of  the  extent  of  intestinal  putrefaction,  since  these  bodies 
arise  only  in  part  from  putrefactive  processes.  He  claims  that  the 
ethereal  sulphuric  acid  excretion  represents  a  form  of  sulphur  metabolism 
which  is  more  in  evidence  upon  a  diet  containing  a  very  small  amount  of 
protein  or  upon  a  diet  containing  absolutely  no  protein.  The  ethereal 
sulphuric  acid  content  of  the  urine  diminishes  as  the  total  sulphur  con- 
tent diminishes  but  the  percentage  decrease  is  much  less.  Therefore 
when  considered  from  the  standpoint  of  the  total  sulphuric  acid  content 
the  ethereal  sulphuric  acid  content  is  not  diminished  but  is  increased, 
although  the  total  sulphuric  acid  content  is  diminished.  Folin's  experi- 
ments also  seem  to  show  that  the  indoxyl  sulphuric  acid  (indoxyl  potas- 
sium sulphate  or  indican)  content  of  the  urine  does  not  originate  to  any 
degree  from  the  metabolism  of  protein  material  but  that  it  arises  in 
great  part  from  intestinal  putrefaction  and  that  the  excretion  of  indoxyl 
sulphuric  acid  may  alone  be  taken  as  a  rough  index  of  the  extent  of  putre- 
factive processes  within  the  intestine.  Indoxyl  sulphuric  acid, 

CH 

'/\ 

HC      C — C(O.SO3H), 

i        II.  •  il 
HC     C      CH 

\/\/ 
CH  NH 


404  PHYSIOLOGICAL  CHEMISTRY 

therefore,  which  occurs  in  the  urine  as  indoxyl  potassium  sulphate  or 
indican, 

CH 


HC      C  —  C(O.S03K), 

I      II        II 
HC      C      CH 

\/\/ 
CH  NH 

is  clinically  the  most  important  of  the  ethereal  sulphuric  acids.  Under 
normal  conditions  from  4  to  20  mg.  of  indican  are  excreted  per  day. 
The  variations  are  due  mainly  to  diet,  a  high  meat  diet  causing  an 
increase  and  a  carbohydrate  diet  a  decrease.  Pathologically  the  great- 
est increases  are  found  in  disorders  involving  increased  putrefaction  and 
stagnation  of  intestinal  contents.  Bacterial  decomposition  of  body 
protein  as  in  gangrene,  putrid  pus  formation,  etc.,  gives  rise  to  an 
increased  indican  excretion. 

It  was  formerly  believed  'that  the  phenol  was  excreted  practically 
quantitatively  in  the  conjugated  form.  Researches  of  Folin  and  Denis1 
seem  to  indicate  that  this  is  not  true.  Only  part  of  the  phenols  formed 
in  intestinal  putrefaction  are  excreted  in  the  conjugated  form,  the 
remainder  being  excreted  as  free  phenol.  The  phenol  output  tends  to 
vary  directly  but  not  proportionally  with  the  protein  ingestion.  The 
total  phenol  excretion  of  normal  men  on  an  ordinary  mixed  diet  aver- 
ages around  0.4  gram  per  day. 

TESTS   FOR   INDICAN2 

i.  Jaffe's  Test—  Nearly  fill  a  test-tube  with  a  mixture  composed  of  equal 
volumes  of  concentrated  HC1  and  the  urine  under  examination.  Add  2-3  c.c. 
of  chloroform  and  a  few  drops  of  a  calcium  hypochlorite  solution,  place  the  thumb 
over  the  end  of  the  test-tube  and  shake  the  tube  and  contents  thoroughly.  The 
chloroform  is  colored  more  or  less,  according  to  the  amount  of  indican  present. 
Ordinarily  a  blue  color  due  to  the  formation  of  indigo-blue  is  produced;  less 
frequently  a  red  color  due  to  indigo-red  may  be  noted. 

Repeat  this  test  on  some  of  this  same  urine  to  which  formaldehyde  has 
been  added.  Is  there  any  variation  in  the  reaction  from  what  you  previously 
obtained  ? 

The  following  represents  the  reaction  (see  also  pages  2  1  5-2  1  6)  : 

1  Folin  and  Denis:  Jour.  Biol.  Chem.,  22,  309,  1915. 

*  The  urine  should  always  be  examined  fresh  if  this  is  possible.  In  any  event  formalde- 
hyde should  never  be  used  as  a  preservative  for  such  urines  as  are  to  be  examined  for  indican 
by  means  of  any  test  involving  hypochlorite  or  potassium  permanganate.  The  formalde- 
hyde through  its  reducing  power  lowers  the  oxidizing  efficiency  of  the  mixture.  The  forma- 
tion of  formic  acid  from  the  aldehyde  may  also  interfere. 


URINE  405 

CH 

/\ 
HC      C      C.OH 

2          |  ||  ||  -   +    20 

HC      C      CH 

\/\/ 
CHNH 

Indoxyl,  CsHvNO. 

CH  CH 

/\  /V 

HC     C      C:0   0:C—  C     CH 

|      ||       |  I      II      I      +  2H*° 

HC     C      C  C    C     CH 

%/\/  \/\/ 

CH  NH  NH  CH 

Indigo-blue,  CuHioNzOz.. 

a.  Obennayer's  Test.-Nearly  fill  a  test-tube  with  a  mixture  composed  of 
equal  volumes  of  Obennayer's  reagent'  and  the  urine  under  examma  on 
Add  2-3  c.c.  of  chloroform,  place  the  thumb  over  the  end  of  the  test-tube  and 
shake  thoroughly.  How  does  this  compare  with  Jaffe's  test  ? 

.  Tolles'  Reaction.'-To  10  c.c.  of  urine  add  i  c.c.  of  a  5  per  cent  afcohohc 
thymo   solution  and  shake.    Add  about  to  c.c.  of  fuming  HC1  contammg  5 
grams  of  ferric  chloride  per  liter.    Shake  again  carefully  and  let  stand  i 
Lutes.    Add  about  4  c.c.  of  chloroform  and  extract  the  p.gment  by  repeated 
gentle  shaking.    The  chloroform  becomes  intensely  violet.    0.0032  rag.  o: 
S^a  be  detected  in  10  c.c.  of  urine.    It  is  much  the  most  dehcate  test  for 

mdican'  CO.NH.CH2.COOH. 

t 

HIPPURIC  ACID, 

This  acid  occurs  normally  in  the  urine  of  both  the  carnivora  and 
herbivora  but  is  much  more  abundant  in  the  urine  of  the  latter, 
formed  by  a  synthesis  of  benzoic  acid  and  glycocoll  which  takes  place 
in  the  kidneys  and  elsewhere.3  The  glycocoll  comes  from  decomposi- 
tion of  protein.  The  benzoic  acid  thus  utilized  may  come  from  (i)  pre- 
formed benzoic  acid  of  fruits  and  vegetables;  (2)  other  aromatic  com- 
pounds of  fruits  and  vegetables;  (3)  aromatic  ammo-acids  (tyrosme 
and  phenylalanine)  from  the  alimentary  tract.  The  average  excretion 
of  hippuric  acid  by  an  adult  man  for  24  hours  under  normal  conditions 
is  about  0.7  gram.  Hippuric  acid  crystallizes  in  needles  or  rhombic 
prisms  (see  Fig.  130,  p.  406)  the  particular  form  depending  upo 

•  Obermayer's  reagent  is  prepared  by  adding  2-4  grams  of  ferric  chloride  to  a  liter  of  con- 
centrated HC1  (sp.  gr.  1.19). 

2  Zeil.  pkysiol.  Chem.,  94,  79>  I9I5- 

»  Kingsbury  and  Bell:  Jour.  Biol.  Chem.,  21,  297, 


406  PHYSIOLOGICAL   CHEMISTRY 

rapidity  of  crystallization.  Pure  hippuric  acid  melts  at  i87°C.  The 
most  satisfactory  method  for  the  isolation  of  hippuric  acid  from  the 
urine  in  crystalline  form  is  that  proposed  by  Roaf  (see  below).  It 
is  easily  soluble  in  alcohol  or  hot  water,  and  only  slightly  soluble  in 
ether.  The  output  of  hippuric  acid  is  increased  in  diabetes  owing  prob- 
ably to  the  ingestion  of  much  protein  and  fruit.  Plums,  prunes  and 
cranberries  in  particular  increase  the  hippuric  acid  output  considerably 
due  to  their  relatively  high  content  of  benzoic  acid.  Hippuric  acid 
is  decreased  in  fevers  and  in  certain  kidney  disorders  where  the  synthetic 


FIG.  130. — HIPPURIC  ACID. 

activity  of  the  renal  cells  is  diminished.     It  may  be  determined  quan- 
titatively by  methods  given  in  Chapter  XXVII. 

EXPERIMENTS  ON  HLPPURIC  ACID 

i.  Separation  from  the  Urine. — (a)  First  Method. — Render  500-1000  c.c. 
of  urine  of  the  horse  or  cow1  alkaline  with  milk  of  lime,  boil  for  a  few  moments  and 
filter  while  hot.  Concentrate  the  filtrate,  over  a  burner,  to  a  small  volume.  Cool 
the  solution,  acidify  it  strongly  with  concentrated  hydrochloric  acid  and  stand  it 
in  a  cool  place  for  24  hours.  Filter  off  the  crystals  of  hippuric  acid  which  have 
formed  and  wash  them  with  a  little  cold  water.  Remove  the  crystals  from  the 
paper,  dissolve  them  in  a  very  small  amount  of  hot  water  and  percolate  the  hot 
solution  through  thoroughly  washed  animal  charcoal,  being  careful  to  wash  out 
the  last  portion  of  the  hippuric  acid  solution  with  hot  water.  Filter,  concentrate 

1  If  urine  of  the  horse  or  cow  is  not  available  human  urine  may  serve  the  purpose  fully 
as  well  provided  means  are  taken  to  increase  its  content  of  hippuric  acid.  This  may  be  con- 
veniently accomplished  by  ingesting  2  grams  of  ammonium  benzoate  at  night.  (See 
chapter  on  Metabolism.)  The  fraction  of  urine  passed  in  the  morning  will  be  found  to  have 
a  high  content  of  hippuric  acid.  The  ammonium  benzoate  is  in  no  way  harmful.  In  case 
ammonium  benzoate  is  not  available  sodium  benzoate  may  be  substituted. 


URINE  407 

the  filtrate  to  a  small  volume  and  stand  it  aside  for  crystallization.  Examine  the 
crystals  under  the  microscope  and  compare  them  with  those  hi  Fig.  130,  page  406. 
This  method  is  not  as  satisfactory  as  Roaf  s  method  (see  below). 

(b)  Roaf  s  Method. — Place  500  c.c.  of  urine  of  the  horse  or  cow  in  a  cas- 
serole or  precipitating  jar  and  add  an  equal  volume  of  a  saturated  solution  of 
ammonium  sulphate1  and  7.5  c.c.  of  concentrated  sulphuric  acid.  Permit  the 
mixture  to  stand  for  24  hours  and  remove  the  crystals  of  hippuric  acid  by  filtra- 
tion. Purify  the  crystals  by  recrystallization  according  to  the  directions  given 
above  under  First  Method.  Examine  the  crystals  under  the  microscope  and 
compare  them  with  those  given  hi  Fig.  130,  page  406. 

If  sufficient  urine  is  not  available  to  permit  the  use  of  500  c.c.  a  smaller  volume 
may  be  used  inasmuch  as  it  is  possible,  by  the  above  technic,  to  isolate  hippuric 
acid  hi  crystalline  form  from  as  small  a  volume  as  25-50  c.c.  of  herbivorous  urine. 
The  greater  the  amount  of  ammonium  sulphate  added  the  more  rapid  the  crystal- 
lization until  at  the  saturation  point  the  crystals  of  hippuric  acid  sometimes  form  hi 
about  ten  minutes. 

2.  Melting-point. — Determine  the  melting-point  of  the  hippuric  acid  pre- 
pared hi  the  above  experiment  (see  page  392). 

3.  Solubility. — Test  the  solubility  of  hippuric  acid  in  hot  and  cold  water  and 
hi  alcohol,  and  ether. 

4.  Formation  of  Nitro-Benzene  (Liicke's  Reaction). — To  a  little  hippuric  acid 
hi  a  small  porcelain  dish  add  1-2  c.c.  of  concentrated  HNO3  and  evaporate  to  dry- 
ness  on  a  water-bath.    Transfer  the  residue  to  a  dry  test-tube,  apply  heat,  and 
note  the  odor  of  the  artificial  oil  of  bitter  almonds  (nitrobenzene). 

5.  Spiro's  Reaction.2 — Warm  the  hippuric  acid  with  acetic  anhydride,  anhy- 
drous sodium  acetate  and  benzaldehyde.    After  one-half  hour  permit  the  solution 
to  cool.    Note  the  formation  of  crystals  of  the  lactimide  of  phenylaminocinnamic 
acid,  melting-point  165-166°.    Heat  some  of  .the  crystals  with  concentrated  sodium 
hydroxide  until  ammonia  is  given  off.    Acidify  and  note  the  formation  of  phenyl- 
pyroracemic  acid  (C6H6CH2.CO.COOH).    This  acid  is  soluble  in  ether. 

6.  Sublimation. — Place  a  few  crystals  of  hippuric  acid  hi  a  dry  test-tube  and 
apply  heat.    The  crystals  are  reduced  to  an  oily  fluid  which  solidifies  in  a  crystal- 
line mass  upon  cooling.    When  stronger  heat  is  applied  the  liquid  assumes  a 
red  color  and  finally  yields  a  sublimate  of  benzoic  acid  and  the  odor  of  hydro- 
cyanic acid. 

7.  Formation  of  Ferric  Salt. — Render  a  small  amount  of  a  solution  of  hip- 
puric acid  neutral  with  dilute  potassium  hydroxide.    Now  add  1-3  drops  of 
neutral  ferric  chloride  solution  and  note  the  formation  of  the  ferric  salt  of  hip- 
puric acid  as  a  cream-colored  precipitate. 

8.  Synthesis  of  Hippuric  Acid. — To  some  of  the  glycocoll  prepared  in  the  last 
experiment  or  furnished  by  the  instructor,  add  a  little  water,  about  i  c.c.  of  benzoyl 
chloride  and  render  alkaline  with  potassium  hydroxide  solution.    Stopper  the  tube 
and  shake  it  until  no  more  heat  is  evolved.    Now  render  strongly  alkaline  with 
potassium  hydroxide  and  shake  the  mixture  until  no  odor  of  benzoyl  chloride  can  be 
detected.    Cool,  acidify  with  hydrochloric  acid;  add  an  equal  volume  of  petroleum 
ether,  and  shake  thoroughly  to  remove  the  benzoic  acid.     (Evaporate  this  solution 
and  note  the  crystals  of  benzoic  acid.    Compare  them  with  those  shown  in  Fig.  132, 
page  413.)    Decant  the  ethereal  solution  into  a  porcelain  dish  and  extract  again 

1 125  grams  of  solid  ammonium  sulphate  may  be  substituted. 
"Spiro:  Zeit,  physiol.  Chem.,  28,  174,  1899. 


408  PHYSIOLOGICAL   CHEMISTRY 

with  ether.  The  hippuric  acid  remains  in  the  aqueous  solution.  Filter  it  off  and 
wash  it  with  a  small  amount  of  cold  water  while  still  on  the  filter.  Remove  it  to 
a  small,  shallow  vessel,  dissolve  it  in  a  small  amount  of  hot  water  and  set  it  aside 
for  crystallization.  Examine  the  crystals  microscopically  and  compare  them  with 
those  in  Fig.  130,  page  406. 

The  chemistry  of  the  synthesis  is  represented  thus: 

CH2-NH2  COC1  OC-NH-CH2-COOH. 

+  HC1. 


1 


:OOH 

Glycocoll.         Benzoyl  chloride.         Hippuric  acid. 

COOH 

OXALIC  ACID,     | 

COOH 

Oxalic  acid  is  a  constituent  of  normal  urine,  about  15-20  mg.  being 
eliminated  in  24  hours.  It  is  present  in  the  urine  as  calcium  oxalate 
which  is  kept  in  solution  through  the  medium  of  the  acid  phosphates. 
The  origin  of  the  oxalic  acid  content  of  the  urine  is  not  well  under- 
stood. When  ingested  it  is  eliminated,  at  least  in  part,  unchanged,  there- 
fore since  many  of  the  common  articles  of  diet,  e.g.,  asparagus,  apples, 
cabbage,  grapes,  lettuce,  rhubarb,  spinach,  tomatoes,  etc.,  contain  oxalic 
acid  (oxalates)  it  seems  probable  that  the  ingested  food  supplies  a  por- 
tion of  the  oxalic  acid  found  in  the  urine.  There  is  also  experimental 
evidence  that  part  of  the  oxalic  acid  of  the  urine  is  formed  within  the 
organism  in  the  course  of  protein  and  fat  metabolism.  It  has  also  been 
suggested  that  oxalic  acid  may  arise  from  an  incomplete  combustion  of 
carbohydrates,  especially  under  certain  abnormal  conditions.  Patho- 
logically, oxalic  acid  is  found  to  be  increased  in  amount  in  diabetes 
mellitus,  in  organic  diseases  of  the  liver,  and  in  various  other  conditions 
which  are  accompanied  by  a  derangement  of  the  oxidation  mechanism. 
An  abnormal  increase  of  oxalic  acid  is  termed  oxaluria.  A  considerable 
increase  in  the  content  of  oxalic  acid  may  be  noted  unaccompanied  by 
any  other  apparent  symptom.  Calcium  oxalate  crystallizes  in  at  least 
two  distinct  forms,  dumb-bells  and  octahedra  (Fig.  140,  page  476). 

EXPERIMENTS 

Preparation  of  Calcium  Oxalate. — First  Method. — Place  200-250  c.c.  of 
urine  in  a  beaker,  add  5  c.c.  of  a  saturated  solution  of  calcium  chloride,  make  the 
urine  slightly  a'cid  with  acetic  acid,  and  stand  the  beaker  aside  in  a  cool  place  for 
24  hours.  Examine  the  sediment  under  the  microscope  and  compare  the  crystal- 
line forms  with  those  shown  in  Fig.  140,  page  476. 

Second  Method.— Proceed  as  above,  replacing  the  acetic  acid  by  an  excess  of 
ammonium  hydroxide  and  filtering  off  the  precipitate  of  phosphates. 


URINE 


NEUTRAL  SULPHUR  COMPOUNDS 


409 


Under  this  head  may  be  classed  such  bodies  as  cystine  (see  page  74), 
oxyproteic  acid,  alloxyproteic  acid,  uroferric  acid,  methyl  mercaptan, 
ethyl  sulphide,  thiocyanates  and  taurine  derivatives.  The  sulphur 
content  of  the  bodies  just  enumerated  is  generally  termed  unoxidized 
or  neutral  sulphur  in  order  that  it  may  not  be  confused  with  the  acid 
or  oxidized  sulphur  which  occurs  in  the  inorganic  sulphuric  acid  and 
ethereal  sulphuric  acid  forms.  Ordinarily  the  neutral  sulphur  content 
of  normal  human  urine  is  5-25  per  cent  of  the  total  sulphur  content 
(see  "Sulphur  Partition"  in  chapter  on  Metabolism).  The  actual 
amount  excreted  may  be  0.2-0.4  grams  per  day,  calculated  as  SO3. 


FIG.  131. — ALLANTOIN,  FROM  CAT'S  URINE. 

a  and  6,  Forms  in  which  it  crystallized  from  the  urine;  c,  recrystallized  allantoin.     (Drawn 
from  micro-photographs  furnished  by  Prof.  Lafayette  B.  Mendel  of  Yale  University.) 

Its  origin  is  mainly  endogenous.  The  excretion  is  fairly  constant  for 
any  given  individual  in  spite  of  dietary  changes.  In  tuberculosis, 
cancer,  cystinuria,  etc.,  the  amount  may  be  relatively  or  absolutely 
increased.  (See  page  422  for  test  for  neutral  sulphur.) 


NH.CH.NH 


ALLANTOIN,  OC 


CO 


NH.CO  NH2 

Allantoin  is  found  in  the  urine  of  practically  all  mammals  including 
man.  In  human  urine  it  occurs  in  very  small  amount  (5-15  mg.  per 
day)  whereas  in  the  case  of  all  other  mammals  investigated  except 
anthropoid  apes,  it  is  the  principal  end-product  of  purine  metabolism 


410  PHYSIOLOGICAL  CHEMISTRY 

and  may  constitute  90  per  cent  or  over  of  the  total  purine  output.1 
Allantoin  is  formed  by  the  oxidation  of  uric  acid  and  the  output  is 
increased  by  the  feeding  of  thymus  or  pancreas  to  lower  animals. 
When  pure  it  crystallizes  in  prisms  (Fig.  131,  page  409)  and  when  impure 
in  granules  and  knobs.  Pathologically,  it  has  been  found  increased  in 
diabetes  insipidus  and  in  hysteria  with  convulsions  (Pouchet).  Mendel 
and  Dakin2  have  shown  that  allantoin  is  optically  inactive  notwith- 
standing the  fact  that  it  contains  an  asymmetric  carbon  atom.  This 
phenomenon  they  believe  to  be  due  to  tautomeric  change.  Wiechowski 
has  suggested  an  excellent  method  for  the  quantitative  determination 
of  allantoin.  (See  Chapter  XXVII.) 

EXPERIMENTS 

1.  Separation  from  the  Urine.3  —  Meissner's  Method.  —  Precipitate  the  urine 
with  baryta  water.    Neutralize  the  filtrate  carefully  with  dilute  sulphuric  acid, 
filter  immediately,  and  evaporate  the  filtrate  to  incipient  crystallization.    Com- 
pletely precipitate  this  warm  fluid  with  95  per  cent  alcohol  (reserve  the  precipi- 
tate).   Decant  or  filter  and  precipitate  the  solution  by  ether.    Combine  the 
ether  and  alcohol  precipitates  and  extract  with  cold  water  or  hot  alcohol;  allan- 
toin remains  undissolved.    Bring  the  allantoin  into  solution  in  hot  water  and 
recrystallize. 

2.  Preparation  from  Uric  Acid.  —  Dissolve  4  grams  of  uric  acid  in  100  c.c.  of 
water  rendered  alkaline  with  potassium  hydroxide.    Cool  and  carefully  add  3 
grams  of  potassium  permanganate.    Filter,  immediately  acidulate  the  filtrate 
with  acetic  acid  and  allow  it  to  stand  in  a  cool  place  over  night.    Filter  off  the 
crystals  and  wash  them  with  water.    Save  the  wash  water  and  filtrate,  unite 
them  and  after  concentrating  to  a  small  volume  stand  away  for  crystallization. 
Now  combine  all  the  crystals  and  recrystallize  them  from  hot  water.    Use  these 
crystals  in  the  experiments  which  follow. 

3.  Microscopical  Examination.  —  Examine  the  crystals  made  in  the  last  ex- 
periment and  compare  them  with  those  shown  in  Fig.  131. 

4.  Solubility.—  Test  the  solubility  of  allantoin  in  cold  and  hot  water,  cold  and 
hot  alcohol  and  in  ether. 

5.  Reaction.  —  Dissolve  a  crystal  in  water  and  test  the  reaction  to  litmus. 

6.  Furfural  Test  (Schiff).—  Place  a  few  crystals  of  allantoin  on  a  test-tablet  or 
in  a  porcelain  dish  and  add  1-2  drops  of  a  concentrated  aqueous  solution  of  fur- 
fural and  1-2  drops  of  concentrated  hydrochloric  acid.    Observe  the  formation  of 
a  yellow  color  which  turns  to  a  light  purple  if  allowed  to  stand.    This  test  is  given 
by  urea  but  not  by  uric  acid. 

7.  Murexide  Test.  —  Try  this  test  according  to  the  directions  given  on  page 
397.    Note  that  allantoin  fails  to  respond. 

8.  Reduction  of  Fehling's  Solution.—  Make  this  test  in  the  usual  way  (see 
433)  except  that  the  boiling  must  be  prolonged  and  excessive.    Ultimately 


1  Wiechowski:  'JDie  Purinstoffe  und  das  Allantoin"  in  Neubauer  and  Huppert's  "Ana- 
lyse des  Hams"  Wiesbaden,  1913. 

2  Mendel  and  Dakin:  Jour.  Biol.  Chem.,  7,  153,  1910. 

*  The  urine  of  the  dog  after  thymus,  pancreas,  or  uric  acid  feeding  may  be  employed. 


URINE  411 

the  allantoin  will  reduce  the  solution.    Compare  with  the  result  on  uric  acid, 
page  398. 

AMINO-ACEDS1 

Certain  of  these  acids  are  always  present  in  normal  urine.  The 
excretion  of  total  amino-acid  nitrogen  by  a  normal  adult  averages 
0.4-1.0  gram  per  day  or  about  2-6  per  cent  of  the  total  nitrogen. 
Free  amino-acid  nitrogen  (see  van  Slyke  procedure,  Chapter  IV)  is 
considerably  less  than  this,  and  ordinarily  constitutes  0.5-1  per  cent 
of  the  total  nitrogen.  The  amount  may  be  largely  increased  in  disorders 
associated  with  tissue  waste,  e.g.,  typhoid,  acidosis,  pronounced  atrophy 
of  the  liver,  etc.  For  tests  on  ammo-acids  see  Chapter  IV. 

AROMATIC  OXYACIDS 

Two  of  the  most  important  of  the  oxy acids  are  parahydroxy- 
phenyl-acetic  acid, 

CH2.COOH, 


OH 

and  parahydroxy-phenyl-propionic  acid, 

CH2.CH2.COOH. 


They  are  products  of  the  putrefaction  of  protein  material  and  tyrosine 
is  an  intermediate  stage  in  their  formation.  Both  these  acids  for  the 
most  part  pass  unchanged  into  the  urine  where  they  occur  normally  in 
very  small  amount.  The  content  may  be  increased  in  the  same  manner 
as  the  phenol  content,  in  particular  by  acute  phosphorus  poisoning.  A 
fraction  of  the  total  aromatic  oxyacid  content  of  the  urine  is  in  combina- 
tion with  sulphuric  acid,  but  the  greater  part  is  present  in  the  form 
of  salts  of  sodium  and  potassium. 

Homogentisic  Acid  or  di-hydroxyphenyl-acetic  acid, 

OH 

CH2.COOH, 

OH 

lFor  a  full  discussion  see  Underbill's  "The  Physiology  of  the  Ammo  Acids,"  Yale 
University  Press,  November,  1915. 


412  PHYSIOLOGICAL   CHEMISTRY 

is  another  important  oxyacid  sometimes  present  in  the  urine.  Under 
the  name  glycosuric  acid  it  was  first  isolated  from  the  urine  by  Prof. 
John  Marshal]  of  the  University  of  Pennsylvania;  subsequently  Bau- 
mann  isolated  it  and  determined  its  chemical  constitution.  It  occurs  in 
cases  of  alcaptonuria.  A  urine  containing  this  oxyacid  turns  greenish- 
brown  from  the  surface  downward  when  treated  with  a  little  sodium 
hydroxide  or  ammonia.  If  the  solution  be  stirred  the  color  very  soon 
becomes  dark  brown  or  even  black.  Homogentisic  acid  reduces 
alkaline  copper  solutions  but  not  alkaline  bismuth  solutions.  Uro- 
leucic  acid  is  similar  in  its  reaction  to  homogentisic  acid. 

Hydroxymandelic  Acid  or  parahydroxyphenyl-glycolic  acid, 

OH 


CH(OH).COOH, 

has  been  detected  in  the  urine  in  cases  of  yellow  atrophy  of  the  liver. 
Kynurenic  Acid  or  7-hydroxy-]8-quinoline  carboxylic  acid, 

CHCOH 


HC     C     C.COOH, 

I      II       I 
HC     C     CH 

\/\/ 
CHN 

is  present  in  the  urine  of  the  dog  and  has  recently  been  detected  by 
Swain  in  the  urine  of  the  coyote.  To  isolate  it  from  the  urine  proceed 
as  follows:  Acidify  the  urine  with  hydrochloric  acid  in  the  proportion 
1:25.  From  this  acid  fluid  both  the  uric  acid  and  the  kynurenic  acid 
separate  in  the  course  of  24-48  hours.  Filter  off  the  combined  crys- 
talline deposit  of  the  two  acids,  dissolve  the  kynurenic  acid  in  dilute 
ammonia  (uric  acid  is  insoluble),  and  reprecipitate  it  with  hydrochloric 
acid.  If  a  solution  containing  kynurenic  acid  be  evaporated  to  dryness 
with  hydrochloric  acid  and  potassium  chlorate,  a  reddish  residue  is 
obtained  which  becomes  first  brownish  green  and  then  emerald  green  on 
adding  ammonia  (Jaffe). 

Kynurenic  acid  may  be  quantitatively  determined  by  Capaldi's 
method.1 

COOH. 

BENZOIC  ACID, 

•  '.'.."  "  •  .N  V  -          "  t 

1  Zeitschrift  fiir  physiologische  Chemie,  23,  92,  1897. 


URINE 


413 


Benzole  acid  has  been  detected  in  the  urine  of  the  rabbit  and  dog.  It  is 
also  said  to  occur  in  human  urine  accompanying  renal  disorders.  The 
benzoic  acid  probably  originates  from  a  fermentative  decomposition  of 
the  hippuric  acid  of  the  urine.  Benzoic  acid  and  glycocoll  are  synthe- 
sized in  the  kidney  and  elsewhere1  to  form  hippuric  acid  (see  page  619). 
Certain  fruits  and  berries  contain  considerable  benzoic  acid;  e.g.,  cran- 
berries have  been  shown  to  contain  0.06  per  cent.2 

EXPERIMENTS 

1.  Solubility. — Test  the  solubility  of  benzoic  acid  in  water,  alcohol,  and  ether. 

2.  Crystalline  Form. — Recrystallize  some  benzoic  acid  from  hot  water,  ex- 
amine the  crystals  under  the  microscope,  and  compare  them  with  those  re- 
produced in  Fig.  132. 


FIG.  132. — BENZOIC  ACID. 

3.  Sublimation. — Place  a  little  benzoic  acid  in  a  test-tube  and  heat  over  a 
flame.    Note  the  odor  which  is  evolved  and  observe  that  the  acid  sublimes  in  the 
form  of  needles. 

4.  Dissolve  a  little  sodium  benzoate  in  water  and  add  a  solution  of  neutral 
ferric  chloride.    Note  the  production  of  a  brownish-yellow  precipitate  (salicylic 
acid  gives  a  reddish-violet  color  under  the  same  conditions).    Add  ammonium 
hydroxide  to  some  of  the  precipitate.    It  dissolves  and  ferric  hydroxide  is  formed. 
Add  a  little  hydrochloric  acid  to  another  portion  of  the  original  precipitate  and 
stand  the  vessel  away  over  night.    What  do  you  observe? 

NUCLEOPROTEIN 

The  nubecula  of  normal  urine  has  been  shown  by  one  investigator 
to  consist  of  a  mucoid  containing  12.7  per  cent  of  nitrogen  and  2.3 
per  cent  of  sulphur.  This  body  evidently  originates  in  the  urinary 

1  Kingsbury  and  Bell:  Jour.  Biol.  Chem.,  21,  297,  1915. 

2  Radin  [quoted  by  Blatherwick  (Arch.  Int.  Med.,  14,  409,  1914)  from  unpublished  data]. 


414  PHYSIOLOGICAL  CHEMISTRY 

passages.  It  is  probably  slightly  soluble  in  the  urine.  Some  investiga- 
tors believe  that  the  body  forming  the  nubecula  of  normal  urine  is 
nucleoprotein  and  not  a  mucin  or  mucoid  as  stated  above.  A  discussion 
of  nucleoprotein  and  related  bodies  occurring  in  the  urine  under  patho- 
logical conditions  will  be  found  on  page  444. 

NH—  CO 

I 
OXALURIC  ACID,  CO 

I 

NH2  COOH. 

Oxaluric  acid  is  not  a  constant  constituent  of  normal  human  urine, 
and  when  found  occurs  only  in  traces  as  the  ammonium  salt.  Upon 
boiling  oxaluric  acid  it  splits  into  oxalic  acid  and  urea. 

GLUCOSE 

This  sugar  occurs  in  traces  in  normal  urine.1  It  is,  however,  not 
present  in  sufficient  concentration  to  be  detected  by  any  of  the  ordinary 
tests  used  in  urine  analysis.  In  certain  pathological  conditions  (pp. 
430  and  539)  the  sugar  in  the  urine  is  notably  increased.  Folin  has 
modified  Benedict's  sugar  test  (see  Chapter  XXIV)  so  it  may  be  used 
to  demonstrate  the  sugar  content  of  normal  urine.2 

Since  glucose  is  constantly  present  in  urine  Benedict3  has  proposed 
that  the  term  "glycosuria"  be  discarded  and  "glycuresis"  be  used 
to  indicate  the  presence  of  an  abnormal  amount  of  sugar  in  the  urine. 
It  is  believed  that  1.5  gram  daily  is  the  maximum  normal  excretion. 

Folin's  Test  for  Sugar  in  Normal  Urine.  —  To  about  10  c.c.  of  urine  in  a  test- 
tube  or  small  flask  add  about  2  grams  of  picric  acid  and  about  2  grams  of  good 
quality  bone-black  (Kahlbaum's  or  Merck's  blood  charcoal),  shake  for  five  minutes, 
and  filter.*  Add  i  or  2  c.c.  of  the  creatinine-free  filtrate  to  about  10  c.c.  of  the 
freshly  mixed  sugar  reagent5  in  a  large  test-tube  (together  with  a  pebble  or  two  to 


:  Lancet,  2,  859,  1913. 
1  Folin:  Jour.  Biol.  Chem.,  22,  327,  1915. 
3Benedict,  Osterberg  and  Neuwirth:  Jour.  Biol.  Chem.,  34,  217,  1918. 

4  Concentrated  urines,  which  give  the  most  trouble  in  testing  for  sugar,  contain  from  3 
to  5  mg.  creatinine  per  c.c.     By  the  above  procedure  the  creatinine  content  is  reduced  to 
practically  nothing—  at  the  most  a  few  hundredths  mg.  per  c.c.  being  left  in  the  nitrate. 
Bone-black  has  very  strong  adsorbing  properties  for  the  picrates  of  creatinine.     By  allowing 
the  urine  and  picric  acid  to  stand  for  a  longer  time  (half  an  hour  or  over  night)  the  addition 
of  bone-black  may  be  omitted  if  desired.     The  nitrate  in  that  case  will  contain  about  o.i 
mg.  per  c.c.,  a  quantity  too  small  to  interfere  with  the  test  for  sugar. 

5  Folin's  Sugar  Reagent.  —  The  reagent  is  made  up  in  two  solutions: 

A.  Five  grams  of  crystallized  copper  sulphate  are  dissolved  in  100  c.c.  of  hot  water  and 
to  the  cooled  solution  are  added  60-70  c.c.  of  pure  glycerol. 

B.  One  hundred  and  twenty-five  grams  of  anhydrous  potassium  carbonate  are  dis- 
solved in  -400  c.c.  of  water. 

One  part  of  the  glycerol-copper  solution  (A)  is  mixed  with  two  parts  of  potassium  car- 
bonate solution  (B).  Only  small  portions  should  be  mixed  at  a  time  as  the  reagent  (after 
mixing)  does  not  keep  but  undergoes  gradual  reduction. 


URINE  415 

prevent  bumping)  and  boil  with  constant  shaking1  for  one  and  one-half  minutes • 
If  the  sugar  present  is  considerable  (above  the  normal  variations),  a  typical  reduc- 
tion is  obtained.  If  the  trace  of  sugar  is  smaller,  but  still  rather  large,  the  whole 
solution  will  become  turbid  as  in  Benedict's  test.  If  no  such  turbidity  is  produced 
and  the  boiling  mixture  remains  clear,  transfer  it  at  once  (i.e.,  while  still  very  hot) 
to  centrifuge  tube  and  centrifuge  for  one  to  two  minutes.  Typical  red  cuprous 
oxide  such  as  is  obtained  with  pure  sugar  solutions  will  be  found  in  the  bottom  of  the 
centrifuge  tube  below  the  green  crystalline  potassium  picrate  which  usually  forms 
as  the  liquid  cools. 

Some  copper  reagents  made  as  described  above  give  a  slight  cuprous  oxide 
sediment  when  boiled  alone,  i.e.,  without  any  added  sugar  or  urine.  When  that  is 
the  case  the  reagent  must  be  boiled  and  centrifuged  once  before  using  it  for  the  test. 

ENZYMES 

Various  types  of  enzymes  produced  within  the  organism  are  excreted 
in  both  the  feces  and  the  urine.  In  this  connection  it  is  interesting  to 
note  that  pepsin,  rennin,  lipase  and  an  amylase  have  been  positively 
identified  in  the  urine.  The  occurrence  of  trypsin  in  the  urine,  at  least 
under  normal  conditions,  is  questioned. 

VOLATILE  FATTY  ACIDS 

Acetic,  butyric,  and  formic  acids  have  been  found  under  normal 
conditions  in  the  urine  of  man  and  of  certain  carnivora  as  well  as  in  the 
urine  of  herbivora.  Normally  they  arise  principally  from  the  fermenta- 
tion of  carbohydrates  and  the  putrefaction  of  proteins.  The  acids  con- 
taining the  fewest  carbon  atoms  (formic  and  acetic)  are  found  to  be 
present  in  larger  percentage  than  those  which  contain  a  larger  number  of 
such  atoms.  The  volatile  fatty  acids  occur  in  normal  urine  in  traces, 
the  total  output  for  24  hours  according  to  older  investigators  varying 
from  0.008  gram  to  0.05  gram. 

Pathologically,  the  excretion  of  volatile  fatty  acids  is  increased  in 
diabetes,  fevers,  and  in  certain  hepatic  diseases  in  which  the  parenchyma 
of  the  liver  is  seriously  affected.  Under  other  pathological  conditions 
the  output  may  be  diminished.  These  variations,  however,  in  the 
excretion  of  the  volatile  fatty  acids  possess  very  little  diagnostic 
value. 

CH3 

PARALACTIC  ACID,    CH(OH) 

COOH. 

1  The  shaking  is  desirable  to  avoid  bumping  and  is  necessary  to  prevent  superheating 
and  consequent  reduction  of  the  reagent  on  the  sides  of  the  test  tube. 


416  PHYSIOLOGICAL  CHEMISTRY- 

Paralactic  acid  is  supposed  to  pass  into  the  urine  when  the  supply 
of  oxygen  in  the  organism  is  diminished  through  any  cause,  e.g.,  in 
eclampsia,  acute  yellow  atrophy  of  the  liver,  carbon-monoxide  poisoning, 
acute  phosphorus  poisoning,  or  epileptic  attacks.  This  acid  has  also 
been  found  in  the  urine  of  healthy  persons  following  the  physical  exercise 
incident  to  prolonged  marching.  Paralactic  acid  has  been  detected  in 
the  urine  of  birds  after  the  removal  of  the  liver.  Underbill  reports  the 
occurrence  of  this  acid  in  the  urine  of  a  case  of  pernicious  vomiting  of 
pregnancy. 

CH2.CO.NH.CH2.COOH. 

PHENACETURIC  ACID, 


Phenaceturic  acid  occurs  principally  in  the  urine  of  herbivorous 
animals.  It  may  be  isolated  from  the  urine  of  the  dog  after  feeding 
phenylacetic  acid.1  It  is  produced  in  the  organism  through  the  synthesis 
of  glycocoll  and  phenylacetic  acid.  It  is  doubtful  if  it  occurs  in  normal 
human  urine  even  after  the  ingestion  of  phenylacetic  acid.  It  may  be 
decomposed  into  its  component  parts  by  boiling  with  dilute  mineral 
acids.  The  crystalline  form  of  phenaceturic  acid  (small  rhombic  plates 
with  rounded  angles)  resembles  one  form  of  uric  acid  crystal. 

HC  =  C  -  CH =  CH-  COOH 

I      I 
UROCANIC  ACID,  HN     N 

NX 

CH 

This  acid  has  been  found  in  the  urine  of  dogs,  but  not  in  human 
urine.  It  is  imidazolyl-acrylic  acid.  Hunter2  found  it  among  the 
pancreatic  digestion  products  of  casein.  It  crystallizes  as  sickle-shaped 
crystals. 

PHOSPHORIZED  COMPOUNDS 

Phosphorus  in  organic  combination  has  been  found  in  the  urine 
in  such  bodies  as  glycerophosphoric  acid,  which  may  arise  from  the 
decomposition  of  lecithin,  and  phosphocarnic  acid.  It  is  claimed  that 
on  the  average  about  2.5  per  cent  of  the  total  phosphorus  elimination 
is  in  organic  combination. 

1  Sherwin:  Dissertation,  Tubingen,  1015. 

2  Hunter:  Jour.  Biol.  Chem.,  n,  537,  1913. 


.  URINE  417 

PIGMENTS 

There  are  at  least  three  pigments  normally  present  in  human  urine. 
These  pigments  are  urochrome,  urobilin,  and  uroerythrin. 

A.  UROCHROME 

This  is  the  principal  pigment  of  normal  urine  and  imparts  the  char- 
acteristic yellow  color  to  that  fluid.  It  is  apparently  closely  related  to 
its  associated  pigment  urobilin  since  the  latter  may  be  readily  converted 
into  urochrome  through  evaporation  of  its  aqueous-ether  solution.  Uro- 
chrome may  be  obtained  in  the  form  of  a  brown,  amorphous  powder 
which  is  readily  soluble  in  water  and  95  per  cent  alcohol.  It  is  less 
soluble  in  absolute  alcohol,  acetone,  amyl  alcohol  and  acetic  ether,  and 
insoluble  in  benzene,  chloroform,  and  ether.  Urochrome  is  said  to  be  a 
nitrogenous  body  (4.2  per  cent  nkrogen),  free  from  iron.  Urochrome 
is  believed  to  be  identical  with  the  yellow.pigment,  lactochrome,  of 
milk  whey.1  The  chromogen  of  urochrome,  i.e.,  urochromogen  is  present 
in  the  urine  in  pulmonary  tuberculosis.  Its  presence  is  said  to  be  of 
prognostic  value  (see  page  467). 

B.  UROBILIN 

Urobilin,  which  was  at  one  time  considered  to  be  the  principal  pig- 
ment of  urine,  in  reality  contributes  little  toward  the  pigmentation  of 
this  fluid.  It  is  claimed  that  no  urobilin  is  present  in  freshly  voided  nor- 
mal urine  but  that  its  precursor,  a  chromogen  called  urobilinogew,  is 
present  and  gives  rise  to  urobilin  upon  decomposition  through  the  in- 
fluence of  light.  It  is  claimed  by  some  investigators  that  there  are 
various  forms  of  urobilin,  e.g.,  normal,  febrile,  physiological,  and  patho- 
logical. Urobilin  is  said  to  be  very  similar  to,  if  not  absolutely  iden- 
tical with,  hydrobilirubin  (see  page  225).  It  may  be  determined 
quantitatively.2 

Urobilin  may  be  obtained  as  an  amorphous  powder  which  varies 
in  color  from  brown  to  reddish-brown,  red  and  reddish-yellow,  depend- 
ing upon  the  way  in  which  it  is  prepared.  It  is  easily  soluble  in  ethyl 
alcohol,  amyl  alcohol,  and  chloroform,  and  slightly  soluble  in  ether, 
acetic  ether,  and  in  water.  Its  solutions  show  characteristic  absorption 
bands  (see  Absorption  Spectra,  Plate  II).  Under  normal  conditions 
urobilin  is  derived  from  the  bile  pigments  in  the  intestine. 

Urobilin  is  increased  in  most  acute  infectious  diseases  such  as  ery- 

1  Palmer  and  Cooledge:  Jour.  Biol.  Chem.,  17,  251,  1914. 
Pelkan:  Jour.  Biol.  Chem.,  43,  237,  1920. 

2  Marcussen  and  Hansen:  Jour.  Biol.  Chem.,  36,  381,  1918. 

27 


41 8  PHYSIOLOGICAL   CHEMISTRY 

sipelas,  malaria,  pneumonia,  and  scarlet  fever.  It  is  also  increased  in 
appendicitis,  carcinoma  of  the  liver,  catarrhal  icterus,  pernicious  anemia, 
in  cases  of  posioning  by  antifebrin,  antipyrin,  pyridin,  and  potas- 
sium chlorate  and  quite  commonly  after  salvarsan  injections.  In 
general  it  is  usually  increased  when  blood  destruction  is  excessive  and 
in  disturbances  of  the  liver.  It  is  markedly  decreased  in  phosphorus 
poisoning. 

In  liver  disease,  of  any  type,  urobilinogen  occurs  in  the  urine.     Its 
detection  is  the  basis  of  a  specific  test  for  functional  liver  incapacity. 

EXPERIMENTS 
c 

1.  Ammoniacal  Zinc  Chloride  Test. — Render  some  of  the  urine  ammoniacal 
by  the  addition  of  ammonium  hydroxide,  and  after  allowing  it  to  stand  a  short 
time  filter  off  the  precipitate  of  phosphates  and  add  a  few  drops  of  zinc  chloride 
solution  to  the  filtrate.    Observe  the  production  of  a  greenish  fluorescence. 
Examine  the  fluid  by  means  of  the  spectroscope  and  note  the  absorption  band 
which  occupies  much  the  same  position  as  the  absorption  band  of  urobilin  in  acid 
solution  (see  Absorption  Spectra,  Plate  II). 

2.  Ether-Absolute  Alcohol  Test. — Mix  urine  and  pure  ether  hi  equal  volumes 
and  shake  gently  in  a  separately  funnel.    Separate  the  ether  extract,  evaporate  it 
to  dryness,  and  dissolve  the  residue  hi  2-3  c.c.  of  absolute  alcohol.    Note  the 
greenish  fluorescence.    Examine  the  solution  spectroscopically  and  observe  the 
characteristic  absorption  band  (see  Absorption  Spectra,  Plate  IE). 

3.  Ring  Test.— Acidify  25  c.c.  of  urine  with  2-3  drops  of  concentrated  hydro- 
chloric acid,  add  5  c.c.  of  chloroform  and  shake  the  mixture.    Separate  the  chloro- 
form, place  it  in  a  test-tube,  and  add  carefully  3-5  c.c.  of  an  alcoholic  solution  of 
zinc  acetate.    Observe  the  formation  of  a  green  ring  at  the  zone  of  contact  of  the 
two  fluids.    If  the  tube  is  shaken  a  fluorescence  may  be  observed. 

4.  Spectroscopic  Examination. — Acidify  the  urine  with  hydrochloric  acid  and 
allow  it  to  remain  exposed  to  the  air  for  a  few  moments.     By  this  means  if  any 
urobilinogen  is  present  it  will  be  transformed  into  urobilin.     The  urine  may  now  be 
examined  by  means  of  the  spectroscope.     If  urobilin  is  present  in  the  fluid  the  char- 
acteristic absorption  band  lying  between  b  and  F  will  be  observed  (see  Absorption 
Spectra,  Plate  II).     It  may  be  found  necessary  to  dilute  the  urine  with  water  before 
a  distinct  absorption  band  is  observed.     This  test  may  be  modified  by  acidifying 
10  c.c.  of  urine  with  hydrochloric  acid  and  shaking  it  gently  with  5  c.c.  of  amyl 
alcohol.     The  alcoholic  extract  when  examined  spectroscopically  will  show  the 
characteristic  urobilin  absorption  band.     (Note  the  spectroscopic  examination  in 
experiment  (i)  above.) 

5.  Iodine  Test  (Gerhardt). — To  20  c.c.  of  urine  add  3-5  c.c.  of  chloroform 
and  shake  well.     Separate  the  chloroform  extract  and  add  to  it  a  few  drops  of 
iodine  solution  (I  in  KI).     Render  the  mixture  alkaline  with  dilute  solution  of 
potassium  hydroxide  and  note  the  production  of  a  yellow  or  yellowish-brown  color. 
The  solution  ordinarily  exhibits  a  greenish  fluorescence. 

6.  Alcoholic  Zinc  Chloride  Test  (Wirsing). — To  20  c.c.  of  urine  add  3-5  c.c. 
of  chloroform  and  shake  gently.     Separate  the  chloroform  extract  and  add  to  it 
a  drop  of  an  alcoholic  solution  of  zinc  chloride.    Note  the  rose-red  color  and  the 


URINE  419 

greenish  fluorescence.     If  the  solution  is  turbid  it  may  be  rendered  clear  by  the 
addition  of  a  few  cubic  centimeters  of  absolute  alcohol. 

C.  UROERYTHRIN 

This  pigment  is  frequently  present  in  small  amount  in  normal  urine. 
The  red  color  of  urinary  sediments  is  due  in  great  part  to  the  presence 
of  uroerythrin.  It  is  easily  soluble  in  amyl  alcohol,  slightly  soluble  in 
acetic  ether,  absolute  alcohol,  or  chloroform,  and  nearly  insoluble  in 
water.  Dilute  solutions  of  uroerythrin  are  pink  in  color  while  concen- 
trated solutions  are  orange  red  or  bright  red;  none  of  its  solutions 
fluoresce.  Uroerythrin  is  increased  in  amount  after  strenuous  physical 
exercise,  digestive  disturbances,  fevers,  certain  liver  disorders,  and  in 
various  other  pathological  conditions. 

PTOMAINES  AND  LEUCOMAINES 

These  toxic  substances  are  said  to  be  present  in  small  amount  in 
normal  urine.  Very  little  is  known  definitely,  however,  about  them. 
It  is  claimed  that  five  different  poisons  may  be  detected  in  the  urine, 
and  it  is  further  stated  that  each  of  these  substances  produces  a  spe- 
cific and  definite  symptom  when  injected  intravenously  into  a  rabbit. 
The  resulting  symptoms  are  narcosis,  salivation,  mydriasis,  paralysis, 
and  convulsions.  The  day  urine  is  principally  narcotic  and  is  2-4  times 
as  toxic  as  the  night  urine  which  is  chiefly  productive  of  convulsions. 

PURINE  BASES 

The  purine  bases  found  in  human  urine  are  adenine,  carnine,  epi- 
guanine,  episarkine,  guanine,  xanthine,  heteroxanthine,  hypoxanthine, 
paraxan thine,  and  i-methylxan thine.  The  main  bulk  of  the  purine 
base  content  of  the  urine  is  made  up  of  paraxanthine,  heteroxanthine 
and  i-methylxanthine,  which  are  derived  for  the  most  part  from  the  caf- 
feine, theobromine,  and  theophylline  of  the  food.  The  total  purine 
base  content  is  made  up  of  the  products  of  two  distinct  forms  of  metabo- 
lism, i.e.,  metabolism  of  ingested  nucleins  and  purines  and  metabolism 
of  tissue  nuclein  material.  Purine  bases  resulting  from  the  first  form  of 
metabolism  are  said  to  be  of  exogenous  origin,  whereas  those  resulting 
from  the  second  form  of  metabolism  are  said  to  be  of  endogenous  origin. 
The  daily  output  of  purine  bases  by  the  urine  is  extremely  small  and 
varies  greatly  with  the  individual  (16-60  mg.) .  The  output  is  increased 
after  the  ingestion  of  nuclein  material  as  well  as  after  the  increased  de- 
struction of  leucocytes.  A  well-marked  increase  accompanies  leukemia. 
Edsall  and  others  have  shown  that  the  output  of  purine  bases  by  the 


420  PHYSIOLOGICAL   CHEMISTRY 

urine  is  increased  as  a  result  of  X-ray  treatment.  The  purine  bases 
form  a  higher  percentage  of  the  total  purine  excretion  in  the  case  of 
the  monkey,  sheep  and  goat  than  in  man. 

EXPERIMENT 

i.  Formation  of  the  Silver  Salts. — Add  an  excess  of  magnesia  mixture1  to 
25  c.c.  of  urine.  Filter  off  the  precipitate  and  add  ammoniacal  silver  solution2 
to  the  filtrate.  A  precipitate  composed  of  the  silver  salts  of  the  various  purine 
bases  is  produced.  The  purine  bases  may  be  determined  quantitatively  by  means 
of  Kruger  and  Schmidt's  method  (see  page  533),  or  Welker's  method  (see  page 
535). 

2.  Inorganic  Physiological  Constituents 
Ammonia 

Next  to  urea,  ammonia  is  the  most  important  of  the  nitrogenous 
end-products  of  protein  metabolism.  Ordinarily  about  2.5-4.5  per 
cent  of  the  total  nitrogen  of  the  urine  is  eliminated  as  ammonia  and 
on  the  average  this  would  be  about  0.7  gram  per  day.  Under  normal 
conditions  the  ammonia  is  present  in  the  urine  in  the  form  of  the 
chloride,  phosphate,  or  sulphate.  This  is  due  to  the  fact  that  combina- 
tions of  this  sort  are  not  oxidized  in  the  organism  to  form  urea,  but  are 
excreted  as  such.  This  explains  the  increase  in  the  output  as  ammonia 
which  follows  the  administration  of  the  ammonium  salts  of  the  mineral 
acids  or  of  the  acids  themselves.  On  the  other  hand,  when  ammonium 
acetate  and  many  other  ammonium  salts  of  certain  organic  acids  are 
administered  no  increase  in  the  output  of  ammonia  occurs  since  the  salt 
is  oxidized  and  its  nitrogen  ultimately  appears  in  the  urine  as  urea. 
Acid-forming  foods  (see  page  613)  also  increase  the  ammonia  output, 
whereas  the  administration  of  alkalies  or  of  base-forming  foods  decreases 
the  excretion  of  ammonia. 

Experiments3  indicate  that  the  nitrogen  in  food  protein  may  in 
part  be  replaced  by  ammonium  salts. 

Copious  water  drinking  increases  the  ammonia  output.  This  fact 
has  been  interpreted  as  indicating  a  stimulation  of  the  gastric  secretion.4 

The  acids  formed  during  the  process  of  protein  destruction  within 
the  body  have  an  influence  upon  the  excretion  of  ammonia  similar  to 

1  Magnesia -mixture  may  be  prepared  as  follows:  Dissolve  175  grams  of  MgSOi  and 
350  grams  of  NEUC1  in  1400  c.c.  of  distilled  water.  Add  700  grams  of  concentrated  NHr 
OH,  mix  very  thoroughly  and  preserve  the  mixture  in  a  glass-stoppered  bottle. 

1  Ammoniacal  silver  solution  may  be  prepared  according  to  directions  given  on  page  627. 

1  Grafe  and  Schlapfer:  Zeit.  physiol.  chem.,  77,  i,  1912,  experiments  by  Abderhalden  in 
same  journal. 

4  Wills  and  Hawk:  Jour.  Am.  Chem.  Soc.,  36,  158,  1914. 


URINE  421 

that  exerted  by  acids  which  have  been  administered.  Therefore  a 
pathological  increase  in  the  output  of  ammonia  is  observed  in  such 
diseases  as  are  accompanied  by  an  increased  and  imperfect  protein 
metabolism,  and  especially  in  diabetes,  in  which  disease  acetoacetic 
acid  and  /3-hydroxy butyric  acid  are  found  in  the  urine  in  combination 
with  the  ammonia. 

Folin  claims  that  a  pronounced  decrease  in  the  extent  of  protein 
metabolism,  as  measured  by  the  total  nitrogen  in  the  urine,  is  frequently 
accompanied  by  a  decreased  elimination  of  ammonia.  The  ammonia 
elimination  is  therefore  probably  determined  by  other  factors  than  the 
total  protein  catabolism  as  such.  Furthermore,  he  believes  that  a 
decided  decrease  in  the  total  nitrogen  excretion  is  always  accompanied 
by  a  relative  increase  in  the  ammonia-nitrogen,  provided  the  food  is  of  a 
character  yielding  an  alkaline  ash. 

The  quantitative  determination  of  ammonia  must  be  made  upon 
the  fresh  urine,  since  upon  standing  the  normal  urine  will  undergo  am- 
moniacal  fermentation  (see  page  379). 

EXPERIMENTS 
(See  Experiment  2  under  Phosphates,  page  426.) 

Sulphates 

Sulphur  in  combination  is  excreted  in  two  forms  in  the  urine:  first, 
as  unoxidized,  loosely  combined  or  neutral  sulphur,  and  second,  as  oxidized 
or  acid  sulphur.  The  unoxidized  or  neutral  sulphur  is  excreted  mainly 
as  a  constituent  of  such  bodies  as  cystine,  cysteine,  taurine,  hydrogen 
sulphide,  ethyl  sulphide,  thiocyanates,  sulphonic  acids,  oxyproteic  acid, 
alloxyproteic  acid,  and  uroferric  acid.  The  amount  of  neutral  sulphur 
eliminated  is  in  great  measure  independent  of  the  extent  of  protein 
decomposition  or  of  the  total  sulphur  excretion.  In  this  characteristic 
it  is  somewhat  similar  to  the  excretion  of  creatinine.  The  oxidized 
sulphur  is  eliminated  in  the  form  of  sulphuric  acid,  principally  as  salts  of 
sodium,  potassium,  calcium,  and  magnesium;  a  relatively  small  amount 
occurs  in  the  form  of  ethereal  sulphuric  acid,  i.e.t  sulphuric  acid  in  com- 
bination with  such  aromatic  bodies  as  phenol,  indole,  skatole,  cresol, 
pyrocatechol,  and  hydroquinol.  Sulphuric  acid  in  combination  with 
Na,  K,  Ca  or  Mg  is  sometimes  termed  inorganic  or  preformed  sulphuric 
acid,  whereas  the  ethereal  sulphuric  acid  is  sometimes  called  conjugate 
sulphuric  acid.  The  greater  part  of  the  sulphur  is  eliminated  in  the 
oxidized  form,  but  the  absolute  percentage  of  sulphur  excreted  as  the 


422  PHYSIOLOGICAL   CHEMISTRY 

preformed,  ethereal  or  loosely  combined  type  depends  upon  the  total 
quantity  of  sulphur  present;  i.e.,  there  is  no  definite  ratio  between 
the  three  forms  of  sulphur  which  will  apply  under  all  conditions.  The 
preformed  sulphuric  acid  may  be  precipitated  directly  from  acidified 
urine  with  BaCl2,  whereas  the  ethereal  sulphuric  acid  must  undergo  a 
preliminary  boiling  in  the  presence  of  a  mineral  acid  before  it  can  be 
so  precipitated. 

The  sulphuric  acid  excreted  in  the  urine  arises  principally  from 
the  oxidation  of  protein  material  within  the  body;  a  relatively  small 
amount  is  due  to  ingested  sulphates.  Under  nprmal  conditions  about 
2.5  grams  of  sulphuric  acid  (SO 3)  are  eliminated  daily,  about  75-95  per 
cent  of  this  being  in  the  form  of  sulphates.  About  90  per  cent  of  this 
sulphate  excretion  is  in  the  form  of  inorganic  sulphate  and  10  per  cent  as 
ethereal  sulphates.  Since  the  sulphuric  acid  content  of  the  urine  has, 
for  the  most  part,  a  protein  origin  and  since  one  of  the  most  important 
constituents  of  the  protein  molecule  is  nitrogen,  it  would  be  reasonable 
to  suppose  that  a  fairly  definite  ratio  might  exist  between  the  excretion 
of  these  two  elements.  However,  when  we  appreciate  that  the  per- 
centage content  of  N  and  S  present  in  different  proteins  is  subject  to 
rather  wide  variations,  the  fixing  of  a  ratio  which  will  express  the  exact 
relation  existing  between  these  two  elements  as  they  appear  in  the  urine 
as  end-products  of  protein  metabolism  is  practically  impossible.  It 
has  been  suggested  that  the  ratio  5 :  i  expresses  this  relation  in  a  general 
way. 

Pathologically,  the  excretion  of  sulphuric  acid  by  the  urine  is  in- 
creased in  acute  fevers  and  in  all  other  diseases  marked  by  a  stimulated 
metabolism,  whereas  a  decrease  in  the  sulphuric  acid  excretion  is  ob- 
served in  those  diseases  which  are  accompanied  by  a  loss  of  appetite 
and  a  diminished  metabolic  activity. 

EXPERIMENTS 

1.  Detection  of  Inorganic  Sulphuric  Acid. — Place  about  10  c.c.  of  urine  in  a 
test-tube,  acidify  with  acetic  acid  and  add  some  barium  chloride  solution.    A 
white  precipitate  of  barium  sulphate  forms. 

2.  Detection  of  Ethereal  Sulphuric  Acid. — Filter  off  the  barium  sulphate 
precipitate  formed  in  the  above  experiment,  add  i  c.c.  of  hydrochloric  acid  and  a 
little  barium  chloride  solution  to  the  filtrate  and  heat  the  mixture  to  boiling  for 
1-2  minutes.  '  Note  the  appearance  of  a  turbidity  due  to  the  presence  of  sul- 
phuric acid  which  has  been  separated  from  the  ethereal  sulphates  and  has  com- 
bined with  the  barium  of  the  BaCl2  to  form  BaSO4. 

3.  Detection  of  Unoxidized  or  Neutral  Sulphur. — Place  about  10  c.c.  of  urine 
in  a  test-tube,  introduce  a  small  piece  of  zinc,  add  sufficient  hydrochloric  acid 
to  cause  a  gentle  evolution  of  hydrogen,  and  over  the  mouth  of  the  tube  place  a 


URINE 


423 


FIG.     133. — CALCIUM     SULPHATE. 
(Hensel  and  Weil.) 


filter  paper  saturated  with  lead  acetate  solution.  In  a  short  time  the  portion  of 
the  paper  in  contact  with  the  vapors  within  the  test-tube  becomes  blackened  due 
to  the  formation  of  lead  sulphide.  The  nascent  hydrogen  has  reacted  with  the 
loosely  combined  or  neutral  sulphur  to  form  hydrogen  sulphide,  and  this  gas  com- 
ing in  contact  with  the  lead  acetate  paper  has  caused  the  production  of  the  black 
lead  sulphide.  Sulphur  in  the  form  of  inorganic  or  ethereal  sulphuric  acid  does 
not  respond  to  this  test.  (For  discussion  of  neutral  sulphur  compounds  see 
page  409.) 

4.  Calcium  Sulphate  Crystals. — Place  10  c.c.  of  urine  in  a  test-tube,  add  10 
drops  of  calcium  chloride  solution  and  allow  the  tube  to  stand  until  crystals  form. 
Examine  the  calcium  sulphate  crystals  under 
the  microscope  and  compare  them  with  those 
shown  in  Fig.  133. 


Chlorides 

Next  to  urea,  the  chlorides  consti- 
tute the  chief  solid  constituent  of  the 
urine.  The  principal  chlorides  found 
in  the  urine  are  those  of  sodium,  potas- 
sium, ammonium,  and  magnesium,  with 
sodium  chlaftide  predominating.  The 

excretion  of  chloride  is  dependent,  in  great  part,  upon  the  nature  of  the 
diet,  but  on  the  average,  the  daily  output  is  about  10-15  grams,  expressed 
as  sodium  chloride.  Copious  water  drinking  increases  the  output  of 
chlorides  considerably.  Because  of  their  solubility,  chlorides  are  never 
found  in  the  urinary  sediment. 

Since  the  amount  of  chlorides  excreted  in  the  urine  is  due  primarily 
to  the  chloride  content  of  the  food  ingested,  it  follows  that  a  decrease 
in  the  amount  of  ingested  chloride  will  likewise  cause  a  decrease  in  the 
chloride  content  of  the  urine.  In  cases  of  actual  fasting  the  chloride 
content  of  the  urine  may  be  decreased  to  a  slight  trace  which  is  derived 
from  the  body  fluids  and  tissues.  Under  these  conditions,  however, 
an  examination  of  the  blood  of  the  fasting  subject  will  show  the  per- 
centage of  chlorides  in  this  fluid  to  be  approximately  normal.  This 
forms  a  very  striking  example  of  the  care  nature  takes  to  maintain  the 
normal  composition  of  the  blood.  There  is  a  limit  to  the  power  of  the 
body  to  maintain  this  equilibrium,  however,  and  if  the  fasting  organism 
be  subjected  to  the  influence  of  diuretics  for  a  time,  a  point  is  reached 
where  the  normal  composition  of  the  blood  can  no  longer  be  maintained 
and  a  gradual  decrease  in  its  chloride*  content  occurs  which  finally  results 
in  death.  Death  is  supposed  to  result  not  so  much  because  of  a  lack  of 
chlorine  as  from  a  deficiency  of  sodium.  This  is  shown  from  the  fact  that 
potassium  chloride,  for  instance,  cannot  replace  the  sodium  chloride 


424  PHYSIOLOGICAL  CHEMISTRY 

of  the  blood  when  the  latter  is  decreased  in  the  manner  above  stated. 
When  this  substitution  is  attempted  the  potassium  salt  is  excreted  at 
once  in  the  urine,  and  death  follows  as  above  indicated. 

Pathologically  the  excretion  of  chlorides  may  be  decreased  in  some 
fevers,  chronic  nephritis,  croupous  pneumonia,  diarrhoea,  certain  stom- 
ach disorders,  and  in  acute  articular  rheumatism.  Any  condition  ac- 
companied by  the  formation  of  an  exudate  (e.g.,  pneumonia)  will  cause 
a  diminished  chloride  output.  In  convalescence  and  with  resolution 
of  the  exudate  the  chloride  excretion  rises  again. 

EXPERIMENT 

Detection  of  Chlorides  in  Urine. — Place  about  5  c.c.  of  urine  in  a  test-tube, 
render  it  acid  with  nitric  acid  and  add  a  few  drops  of  a  solution  of  silver  nitrate. 
A  white  precipitate,  due  to  the  formation  of  silver  chloride,  is  produced.  This 
precipitate  is  soluble  in  ammonium  hydroxide. 

Phosphates 

Phosphoric  acid  exists  in  the  urine  in  two  general  forms:  First, 
that  in  combination  with  the  alkali  metals,  sodium  and  potassium, 
and  the  radical  ammonium;  second,  that  in  combination  with  the 
alkaline  earth  metals,  calcium  and  magnesium.  Phosphates  formed 
through  a  union  of  phosphoric  acid  with  the  alkali  metals  are  termed 
alkaline  phosphates,  or  phosphates  of  the  alkali  metals,  whereas  phos- 
phates formed  through  a  union  of  phosphoric  acid  with  the  alkaline 
earth  metals  are  termed  earthy  phosphates  or  phosphates  of  the  alkaline 
earth  metals. 

Three  series  of  salts  are  formed  by  phosphoric  acid:  Normal, 
MsPOi,1  mono-hydrogen,  M2HP04,  and  di-hydrogen,  MH2PO4.  The  di- 
hydrogen  salts  are  acid  in  reaction,  and  it  is  claimed  that  about  60  per 
cent  of  the  total  phosphate  content  of  the  urine  is  in  the  form  of  this 
type  of  salt,  and  that  the  acidity  of  the  urine  is  due  in  great  part  to  the 
presence  of  sodium  di-hydrogen  phosphate  (see  page  378).  Henderson2 
maintains  that  " determinations  of  hydrogen  ionization  in  urine  and  its 
behavior  toward  indicators  both  support  the  view  that  in  urine  there 
exists  a  mixture  of  mono-  and  di-hydrogen  phosphates  of  sodium, 
ammonium  and  other  bases." 

In  bones"  the  phosphates  occur  principally  in  the  form  of  the  normal 
salts  of  calcium  and  magnesium.  The  mono-hydrogen  salts  as  a  class 
are  alkaline  in  reaction  to  litmus,  and  it  is  to  the  presence  of  di-sodium 

1  M  may  be  occupied  by  any  of  the  alkali  metals  or  alkaline  earth  metals. 

2  Henderson:  Am.  Jour.  Physiol.,  15,  257,  1906. 


URINE  425 

hydrogen  phosphate,  Na2HP04,  that  the  greater  part  of  the  alkalinity 
of  the  saliva  is  due. 

The  excretion  of  phosphoric  acid  is  extremely  variable,  but  on  the 
average  the  total  output  for  24  hours  is  about  2.5  grams,  expressed 
as  PzO&.  Ordinarily  the  total  output  is  mainly  in  the  form  of  phosphates 
and  is  distributed  between  alkaline  phosphates  and  earthy  phosphates 
approximately  in  the  ratio  2:1.  The  organic  phosphorus  of  the  urine 
constitutes  only  1-4  per  cent  of  the  total  phosphorus  content.  The 
greater  part  of  this  phosphoric  acid  arises  from  the  ingested  food,  either 
from  the  preformed  phosphates  or  more  especially  from  the  phosphorus 
in  organic  combination  such  as  we  find  it  in  phospho-proteins,  nucleo- 
proteins  and  lecithins;  the  phosphorus-containing  tissues  of  the  body 
also  contribute  to  the  total  output  of  this  element.  Alkaline  phosphates 
ingested  with  the  food  have  a  tendency  to  increase  the  phosphoric  acid 
content  of  the  urine  to  a  greater  extent  than  the  earthy  phosphates  so 
ingested.  This  is  due,  in  a  measure,  to  the  fact  that  a  portion  of  the 
earthy  phosphates,  under  certain  conditions,  may  be  precipitated  in  the 
intestine  and  excreted  in  the  feces;  this  is  especially  to  be  noted  in  the 
case  of  herbivorous  animals.  Since  the  extent  to  which  the  phosphates 
are  absorbed  in  the  intestine  depends  upon  the  form  in  which  they  are 
present  in  the  food,  under  ordinary  conditions,  there  can  be  no  absolute 
relationship  between  the  urinary  output  of  nitrogen  and  phosphorus. 
If  the  diet  is  constant,  however,  from  day  to  day,  thus  allowing  of  the 
preparation  of  both  a  nitrogen  and  a  phosphorus  balance,1  a  definite 
ratio  may  be  established.  In  experiments  upon  dogs  which  were  fed 
an  exclusive  meat  diet,  the  ratio  of  nitrogen  to  phosphorus,  in  the  urine 
and  feces,  was  found  to  be  8.1  :i. 

It  has  been  demonstrated  by  recent  investigation  that  the  ingestion 
of  inorganic  phosphorus  compounds  may  give  rise  to  organic  phosphorus 
compounds  such  as  lecithin,  phosphatides,  nucleoproteins  and  phospho- 
proteins.  This  is  an  instance  of  an  organic  substance  synthesized  from 
an  inorganic  substance.  The  experiments  have  been  made  principally 
on  ducks2  and  hens.3 

Pathologically  the  excretion  of  phosphoric  acid  is  increased  in  such 
diseases  of  the  bones  as  diffuse  periostosis,  osteomalacia,  and  rickets; 
according  to  some  investigators,  in  the  early  stages  of  pulmonary  tuber- 
culosis, in  acute  yellow  atrophy  of  the  liver,  in  diseases  which  are  ac- 
compained  by  an  extensive  decomposition  of  nervous  tissue,  and  after 

1  In  metabolism  experiments,  a  statement  showing  the  relation  existing  between  the 
nitrogen  content  of  the  food  on  the  one  hand  and  that  of  the  urine  and  feces  on  the  other, 
for  a  definite  period,  is  termed  a  nitrogen  balance  or  a  "  balance  of  the  income  and  outgo  of 


nitrogen"  (see  chapter  on  Metabolism,  p.  625). 
2  Fingerling:  Biochem.  Zeit.,  38, 


448,  1912. 
1  McCollum  and  Halpin:  Jour.  Biol.  Chem.,  n,  47  (Proceedings),  1912. 


426    -  PHYSIOLOGICAL   CHEMISTRY 

sleep  induced  by  potassium  bromide  or  chloral  hydrate  (Mendel).  It 
is  also  increased  after  copious  water  drinking.  A  decrease  in  the 
excretion  of  phosphates  is  at  times  noted  in  febrile  affections,  such  as 
the  acute  infectious  diseases,  in  pregnancy,  in  the  period  during  which 
the  fetal  bones  are  forming,  and  in  diseases  of  the  kidneys,  because  of 
non-elimination. 

The  so-called  "phosphaturias"  many  times  represent  decreased 
acidity  and  not  increased  phosphate  content  of  the  urine.  Such  con- 
ditions are,  however,  significant  as  indicating  a  possible  tendency  to  the 
formation  of  phosphatic  calculi. 

EXPERIMENTS 

i.  Formation  of  "Triple  Phosphate." — Place  some  urine  in  a  beaker,  render 
it  alkaline  with  ammonium  hydroxide,  add  a  small  amount  of  magnesium  sul- 


FIG.  134. — "TRIPLE  PHOSPHATE."     (Ogden.) 

phate  solution  and  allow  the  beaker  to  stand  in  a  cool  place  over  night.  Crystals 
of  ammonium  magnesium  phosphate,  "triple  phosphate,"  form  under  these  con- 
ditions. Examine  the  crystalline  sediment  under  the  microscope  and  compare 
the  forms  of  the  crystals  with  those  shown  in  Fig.  134,  above. 

2.  Ammoniacal  Fermentation. — Stand  some  urine  aside  in  a  beaker  for 
several  days.    Ammoniacal  fermentation  will  develop  and  "triple  phosphate" 
crystals  will  form. 

(a)  Examine  the  sediment  under  the  microscope  and  compare  the  crystals 
with  those  shown  in  Fig.  134. 

(b)  Hold  a  glass  rod  dipped  in  concentrated  hydrochloric  acid  near  the 
surface  of  the  urine.    Note  the  fumes  of  ammonium  chloride. 

(c)  Insert  a.  strip  of  red  litmus  paper  in  the  urine.    Permit  the  paper  to  dry. 
Note   the  gradual  restoration  of  red  color,  due  to  volatilization  of  ammonia 
(volatile  alkali).    Run  a  control  test  using  0.5  per  cent  Na2CO3  (fixed  alkali). 

3.  Detection  of  Earthy  Phosphates. — Place  10  c.c.  of  urine  in  a  test-tube  and 
render  it  alkaline  with  ammonium  hydroxide.    Warm  the  mixture  and  note  the 
separation  of  a  precipitate  of  earthy  phosphates. 


URINE  427 

4.  Detection  of  Alkaline  Phosphates. — Filter  off  the  earthy  phosphates  as 
formed  in  the.last  experiment,  and  add  a  small  amount  of  magnesia  mixture  (see 
page  637)  to  the  filtrate.    Now  warm  the  mixture  and  observe  the  formation  of  a 
white  precipitate  due  to  the  presence  of  alkaline  phosphates.    Note  the  differenc  e 
in  the  size  of  the  precipitates  of  the  two  forms  of  phosphates  from  this  same  vol- 
ume of  urine.    Which  form  of  phosphates  was  present  hi  the  larger  amount, 
earthy  or  alkaline? 

5.  Influence  upon  Fehling's  Solution. — Place  2  c.c.  of  Fehling's  solution  in  a 
test-tube,  dilute  it  with  4  volumes  of  water  and  heat  to  boiling.    Add  a  solution 
of  sodium  dihydrogen  phosphate,  NaH2PO4,  a  small  amount  at  a  time,  and  heat 
after  each  addition.    What  dd  you  observe?    What  does  this  observation  force 
you  to  conclude  regarding  the  interference  of  phosphates  hi  the  testing  of  dia- 
betic urine  by  means  of  Fehling's  test? 

Sodium  and  Potassium 

The  elements  sodium  and  potassium  are  always  present  in  the  urine. 
Usually  they  are  combined  with  such  acidic  radicals  as  Cr,  CO 3,  SO^ 
and  P04.  The  amount  of  potassium,  expressed  as  K20,  excreted  in 
24  hours  by  an  adult,  subsisting  upon  a  mixed  diet,  is  on  the  average 
2-3  grams,  whereas  the  amount  of  sodium,  expressed  as  Na20,  under 
the  same  conditions,  is  ordinarily  4-6  grams.  The  ratio  of  K  to  Na  is 
generally  about  3:5.  The  absolute  quantity  of  these  elements  excreted 
depends,  of  course,  in  large  measure  upon  the  nature  of  the  diet.  Be- 
cause of  the  non-ingestion  of  NaC  anfl  the  accompanying  destruction 
of  potassium-containing  body  tissues,  the  urine  during  fasting  contains 
more  potassium  salts  than  sodium  salts. 

Pathologically  the  output  of  potassium,  in  its  relation  to  sodium, 
may  be  increased  during  fever;  following  the  crisis,  however,  the  out- 
put of  this  element  may  be  decreased.  It  may  also  be  increased  in 
conditions  associated  with  acidosis. 

Calcium  and  Magnesium 

The  greater  part  of  the  calcium  and  magnesium  excreted  in  the 
urine  is  in  the  form  of  phosphates.  The  daily  output  of  calcium,  which 
depends  principally  upon  the  nature  of  the  diet,  aggregates  on  the 
average  about  0.1-0.4  gram,  (expressed  as  CaO)  per  day.  The  per- 
centage of  calcium  salts  present  in  the  urine  at  any  one  time  (10-40 
per  cent  of  total  calcium  output)  forms  no  dependable  index  as  to  the 
absorption  of  this  class  of  salts,  since  they  are  again  excreted  into  the 
intestine  after  absorption.  It  is  therefore  impossible  to  draw  any  satis- 
factory conclusions  regarding  the  excretion  of  calcium  unless  we  obtain 
accurate  analytical  data  from  both  the  feces  and  the  urine. 


428 


PHYSIOLOGICAL   CHEMISTRY 


Myers  and  Fine1  have  reported  data  showing  a  comparison  of  the 
kidney  and  intestine  as  excretory  routes  for  various  inorganic  constit- 
uents. Their  finding  in  this  connection  are  summarized  in  the  follow- 
ing table: 


Number 

Moisture  con- 

Fecal output  in  per  cent  of  total  output  of  both 
and  feces. 

urine 

of 

tent  of  feces 

cases 

per  cent. 

H2O 

N 

S 

Cl 

P     - 

Ca 

Mg 

K 

5 

76 

6 

10 

10 

3 

36 

90 

72 

18 

9 

84                   16 

15 

iQ 

9 

33 

89 

68 

27 

It  is  not  believed  that  the  findings  differed  especially  from  the 
normal,  except  in  that  group  of  cases  which  suffered  from  intestinal 
diarrhea.  The  average  findings  in  five  cases  with  well  formed  stools, 
74  to  79  per  cent,  moisture,  and  those  with  diarrheal  stools,  79  to  89 
per  cent,  moisture  have  been  grouped  separately  in  the  table. 

Very  little  is  known  positively  regarding  the  actual  course  of  the 
excretion  of  the  calcium  under  pathological  conditions.  An  excess 
is  found  in  some  diseases  of  the  bones,  e.g.,  osteomalacia.  In  others 
as  in  rickets  the  urinary  excretion  may  be  very  low. 

The  daily  excretion  of  magnesium  by  way  of  the  urine  usually 
amounts  to  between  o.i  and  0.3  gram,  expressed  as  MgO.  The  amount 
depends  mainly  on  the  diet.  About  50  per  cent  or  more  of  the  excreted 
magnesium  is  usually  eliminated  by  the  kidneys,  the  remainder  passes 
out  in  the  feces.  There  may  be  a  retention  of  magnesium  in  certain 
bone  disorders  accompanying  a  loss  of  calcium;  in  osteomalacia  for 
example.  Thus  the  excretion  of  calcium  and  magnesium  do  not  neces- 
sarily run  parallel. 

Carbonates 

Carbonates  generally  occur  in  small  amount  in  the  urine  of  man 
and  carnivora  under  normal  conditions,  whereas  much  larger  quanti- 
ties are  ordinarily  present  in  the  urine  of  herbivora.  The  alkaline 
reaction  of  the  urine  of  herbivora  is  dependable  in  great  measure  upon 
the  presence- of  carbonates.  In  general  a  urine  containing  carbonates 
in  appreciable  amount  is  turbid  when  passed  or  becomes  so  shortly 
after.  These  bodies  ordinarily  occur  as  alkali  or  alkaline  earth  com- 
pounds and  the  turbid  character  of  urine  containing  them  is  usually 

1  Myers  and  Fine:  Proc  Soc.  Exp.  Biol.  and  Med.,  16,  73,  1919. 


URINE  429 

due  principally  to  the  latter  class  of  substances.     The  carbonates  of 
the  alkaline  earths  are  often  found  in  amorphous  urinary  sediments. 

Iron 

Iron  is  present  in  small  amount  in  normal  urine.  It  probably  occurs 
partly  in  inorganic  and  partly  in  organic  combination.  The  iron  con- 
tained in  urinary  pigments  or  chromogens  is  in  organic  combination. 
According  to  different  investigators  the  iron  content  of  normal  urine  will 
probably  not  average  more  than  1-5  mg.  per  day.  After  splenectomy 
there  is  an  increased  loss  of  iron  from  the  body  particularly  by  way  of 
the  feces  (Asher). 

EXPERIMENT 

Detection  of  Iron  in  Urine. — Evaporate  a  convenient  volume  (10-15  c-c-)  °f 
urine  to  dryness.  Incinerate  and  dissolve  the  residue  in  a  few  drops  of  iron-free 
hydrochloric  acid  and  dilute  tne  acid  solution  with  5  c.c.  of  water.  Divide  the 
acid  solution  into  two  parts  and  make  the  following  tests:  (a)  To  the  first  part  add 
a  solution  of  ammonium  thiocyanate;  a  red  color  indicates  the  presence  of  iron. 
(b)  To  the  second  part  of  the  solution  add  a  little  potassium  ferrocyanide  solution; 
a  precipitate  of  Prussian  blue  forms  upon  standing. 

Fluorides,  Nitrates,  Silicates  and  Hydrogen  Peroxide 

These  substances  are  all  found  in  traces  in  human  urine  under  nor- 
mal conditions.  Nitrates  are  undoubtedly  introduced  into  the  organ- 
ism in  the  water  and  ingested  food.  The  average  excretion  of  nitrates 
is  about  0.5  gram  per  day,  the  output  being  the  largest  upon  a  vege- 
table diet  and  smallest  upon  a  meat  diet.  Nitrites  are  found  only  in 
urine  which  is  undergoing  decomposition  and  are  formed  from  nitrates 
in  the  course  of  ammoniacal  fermentation.  Hydrogen  peroxide  has 
been  detected  in  the  urine,  but  its  presence  is  believed  to  possess  no 
pathological  importance. 


CHAPTER  XXIV 


URINE:    PATHOLOGICAL    CONSTITUENTS1 


Glucose. 


Proteins 


Blood 
Pus. 


Serum  albumin. 
Serum  globulin. 

Proteoses. 

Peptone. 

Nucleoprotein. 

Fibrin. 

Oxyhemoglobin. 
|  Form  elements. 
I  Pigment. 


Deutero-proteose. 
Hetero-proteose. 
"Bence- Jones'  protein." 


Bile. 


f  Pigments. 

}  Acids. 
Creatine.2 
Acetone. 
Acetoacetic  acid 
/3-Hydroxy  butyric  acid 
Conjugate  glycuronates. 
Pentoses. 
Fat. 

Hema  toporphy  rin . 
Lactose. 
Galactose. 
Fructose. 
Arsenic. 
Mercury. 
Inositol. 
Laiose. 
Melanin. 
Urorosein. 
Nephrorosein. 
*J*  'Urochromogen. 

Unknown  substances. 

1  See  note  at  the  bottom  of  page  386. 

1  Normal  constituent  of  urine  of  infants  and  children. 

430 


URINE  431 

GLUCOSE 

Traces  of  this  sugar  occur  in  normal  urine,1  but  the  amount  is  not 
sufficient  to  be  readily  detected  by  the  ordinary  simple  qualitative 
tests.  There  are  two  distinct  types  of  pathological  glycosuria,2  i.e., 
transitory  glycosuria  and  persistent  glycosuria.  The  transitory  type 
may  follow  the  ingestion  of  an  excess  of  sugar,  causing  the  assimilation 
limit  to  be  exceeded,  or  it  may  accompany  any  one  of  several  disorders 
which  cause  impairment  of  the  power  of  assimilating  sugar.  In  the 
persistent  type  large  amounts  of  sugar  are  excreted  daily  in  the  urine 
for  long  periods  of  time.  Under  such  circumstances  a  condition  known 
as  diabetes  nielli  tus  exists.  In  this  disorder  the  urine  may  contain  10 
per  cent  of  glucose  and  the  average  sugar  content  is  3-5  per  cent. 
Ordinarily,  diabetic  urine  which  contains  a  high  percentage  of  sugar 
possesses  a  faint  yellow  color,  a  nigh  specific  gravity,  and  a  volume 
which  is  above  normal.  Over  100  grams  of  sugar  are  daily  eliminated 
in  some  severe  cases  of  diabetes  mellitus. 

EXPERIMENTS 

The  various  tests  for  glucose  in  the  urine  which  are  embraced  in  the 
experiments  given  herewith  are  based  upon  one  of  the  following 
properties  of  this  sugar: 

(1)  Its  power  to  reduce  the  oxides  of  certain  metals  in  alkaline  solution. 

(2)  Its  power  to  rotate  the  plane  of  polarized  light. 

(3)  Its  power  to  form  crystalline  osazones  with  phenylhydrazine. 

(4)  Its  ability  to  ferment  with  ordinary  yeast. 

i.  Phenylhydrazine  Reaction.— Test  the  urine  according  to  one  of  the  fol- 
lowing methods :  (a)  To  a  small  amount  of  phenylhydrazine  mixture  (enough  to 
fill  the  rounded  portion  of  a  small  test-tube),  furnished  by  the  instructor,3  add 
5  c.c.  of  the  urine,  shake  well,  and  heat  on  a  boiling  water-bath  for  one-half  to 
three-quarters  of  an  hour.  Allow  the  tube  to  cool  slowly  (not  under  the  tap)  and 
examine  the  crystals  microscopically  (Plate  III,  opposite  page  22).  If  the  solu- 
tion has  become  too  concentrated  in  the  boiling  process  it  will  be  light  red  in  color 
and  no  crystals  will  separate  until  it  is  diluted  with  water. 

In  case  doubtful  results  are  obtained  by  this  test  owing  to  the  presence 
of  interfering  substances,  the  urine  should  be  clarified  and  the  test  repeated. 
To  clarify  the  urine  introduce  10  c.c.  into  a  test-tube,  add  i  gram  of  pure  blood 
charcoal,  heat  to  boiling  and  allow  to  stand  with  occasional  shaking  for  five 
minutes.  Use  the  filtrate  in  the  test. 

1Cole:  Lancet,  2,  859,  1913; 
Folin:  Jour.  Biol.  Chem.,  22,  327,  1915. 

inasmuch  as  urine  always  contain  sugar  Benedict,  Osterberg  and  Neuwirth  (Jour. 
Biol.  Chem.,  34,  217,  1918)  suggest  that  the  term  "glycuresis"  should  replace  "glycosuria" 
as  indicating  an  increased  excretion  of  sugar. 

3  This  mixture  is  prepared  by  combining  two  parts  of  phenylhydrazine-hydrochloride 
and  three  parts  of  soch'um  acetate,  by  weight.  These  are  thoroughly  mixed  in  a  mortar. 


432 


PHYSIOLOGICAL  CHEMISTRY 


Yellow  crystalline  bodies  called  osazones  are  formed  from  certain 
sugars  under  these  conditions,  in  general  each  individual  sugar  giving 
rise  to  an  osazone  of  a  definite  crystalline  form  which  is  typical  for  that 
sugar. 

It  is  important  to  remember  in  this  connection  that,  of  the  simple 
sugars  of  interest  in  physiological  chemistry,  glucose  and  fructose  yield 
the  same  osazone,  with  phenylhydrazine.  Each  osazone  has  a  definite 
melting-point,  and  as  a  further  and  more  accurate  means  of  identifica- 
tion it  may  be  recrystallized  and  identified  by  the  determination  of  its 
melting-point  and  nitrogen  content.  The  reaction  taking  place  in  the 
formation  of  phenylglucosazone  is  as  follows : 


CH2OH 

(CHOH); 


CHOH 

y° 

C 
\H 

Glucose 

CH2OH 


+C6H6NH-NH2- 


CH2OH 

I 
(CHOH)3 

CHOH 


+C6H6NH  NH2-» 


Phenylhydrazine 


C 
\H 

Phenylhydrazone 

CH2OH 


(CHOH)  3 
C=0 


+C6H6NHNH2-» 
NHC6H5  +  C6H5NH2+NH3 


C 

\ 


H 


Aniline 


Ammonia 


(CHOH)  3 

C  =  NNHC6H5 
[yN-NHCeH, 

C 

Glucosazone 


(b)  Place  5  c.c.  of  the  urine  in  a  test-tube,  add  i  c.c.  of  phenylhydrazine- 
acetate  solution  furnished  by  the  instructor,1  and  heat  on  a  boiling  water-bath 
for  one-half  to  three-quarters  of  an  hour.  Allow  the  liquid  to  cool  slowly  and 
examine  the  crystals  microscopically  (Plate  HI,  opposite  page  22). 

The  phenylhydrazine  test  has  been  so  modified  by  Cipollina  as  to 
be  of  use  as  a  rapid  clinical  test.  The  directions  for  this  test  are  given 
in  the  next  experiment. 

2.  Reduction  Tests.— To  their  aldehyde  or  ketone  structure,  many 
sugars  owe  the  property  of  readily  reducing  the  alkaline  solutions  of  the 
oxides  of  metals  like  copper,  bismuth,  and  mercury;  they  also  possess 
the  property  of  reducing  ammoniacal  silver  solutions  with  the  separa- 
tion of  metallic  silver.  Upon  this  property  of  reduction  the  most  widely 

^ l  This  solution  is  prepared  by  mixing  one  part  by  volume,  in  each  case  of  glacial  acetic 
acid,  one  part  of  water  and  two  parts  of  phenylhydrazine  (the  base). 


URINE  433 

used  tests  for  sugars  are  based.  When  whitish-blue  cupric  hydroxide  in 
suspension  in  an  alkaline  liquid  is  heated  it  is  converted  into  insoluble 
black  cupric  oxide,  but  if  a  reducing  agent  like  certain  sugars  be  present 
the  cupric  hydroxide  is  reduced  to  insoluble  yellow  or  red  cuprous 
oxide.  These  changes  are  indicated  as  follows: 
OH 

/       - 
Cu          ->Cu 

V  Cupric  oxide 

OH 

Cupric  hydroxide 

(whitish-blue). 
Reaction  in  absence 
of  a  reducing  agent. 

OH 


2Cu  ->  Cu20+2H20+0. 

Cuprous  oxide 
(yellow  to  red). 


V  Cuprous  oxide 

N  (yello 

OH 

Cupric  hydroxide. 
Reaction  in  presence 
of  a  reducing  agent. 

The  chemical  equations  here  discussed  are  exemplified  in  Trommer's 
and  Fehling's  tests. 

(a)  Trommer's  Test.  —  To  5  c.c.  of  urine  in  a  test-tube  add  one-half  its  volume 
of  KOH  or  NaOH.    Mix  thoroughly  and  add,  drop  by  drop,  agitating  after  the 
addition  of  each  drop,  a  very  dilute  solution  of  copper  sulphate.     Continue  the  addi- 
tion until  there  is  a  slight  permanent  precipitate  of  cupric  hydroxide  and  in  conse- 
quence the  solution  is  slightly  turbid.    Heat/and  the  cupric  hydroxide  is  reduced 
to  yellow  or  brownish-red  cuprous  oxide. 

If  the  solution  of  copper  sulphate  used  is  too  strong,  a  small  brownish-red  pre- 
cipitate, produced  in  the  presence  of  a  low  percentage  of  glucose,  may  be  entirely 
masked.  On  the  other  hand,  if  too  little  copper  sulphate  is  used,  a  light-colored 
precipitate,  formed  by  uric  acid  and  purine  bases,  may  obscure  the  brownish-red 
precipitate  of  cuprous  oxide.  The  action  of  KOH  or  NaOH  in  the  presence  of  an 
excess  of  sugar  and  insufficient  copper  will  produce  a  brownish  color.  Phosphates 
of  the  alkaline  earths  may  also  be  precipitated  in  the  alkaline  solution  and  be  mis- 
taken for  cuprous  oxide.  Trommer's  test  is  not  very  satisfactory. 

Salkowski1  has  proposed  a  modification  of  the  Trommer  procedure  which  he 
claims  is  a  very  accurate  sugar  test. 

(b)  Fehling's  Test—  To  about  i  c.c.  of  Fehling's  solution2  in  a  test-tube  add 
about  4  c.c.  of  water,  and  boil.3    [The  cupric  hydroxide  is  held  in  solution  by  the 

1  Salkowski:  Zeit.  physiol.  Chem.,  79,  164,  1912. 

2  Fehling's  solution  is  composed  of  two  definite  solutions  —  a  copper  sulphate  solution 
and  an  alkaline  tartate  solution,  which  may  be  prepared  as  follows: 

Copper  sulphate  solution  =  34.65  grams  of  copper  sulphate  dissolved  in  water  and  made 
up  to  500  c.c. 

Alkaline  tartrate  solution  =  125  grams  of  potassium  hydroxide  and  173  grams  of  Rochelle 
salt  dissolved  in  water  and  made  up  to  500  c.c. 

These  solutions  should  be  preserved  separately  in  rubber-stoppered  bottles  and  mixed 
in  equal  volumes  when  needed  for  use.  This  is  done  to  prevent  deterioration. 

3  More  dilute  Fehling's  solution  should  be  used  in  testing  urines  containing  small  amounts 
of  sugar.     In  case  of  urines  containing  a  high  concentration  of  sugar  it  may  sometimes  be 
desirable  to  use  a  larger  volume  of  Fehling's  solution. 

28 


434  PHYSIOLOGICAL   CHEMISTRY 

sodium  potassium  tartrate  (Rochelle  salt).]  This  is  done  to  determine  whether 
the  solution  will  of  itself  cause  the  formation  of  a  precipitate  of  brownish-red 
cuprous  oxide.  If  such  a  precipitate  forms,  the  Fehling's  solution  must  not  be 
used.  Add  urine L  to  the  hot  Fehling's  solution,  a  few  drops  at  a  time,  and  heat  the 
mixture  to  boiling  after  each  addition  (never  add  more  urine  than  the  original 
volume  of  Fehling's  solution).  The  production  of  yellow  or  brownish-red  cup- 
rous oxide  indicates  that  reduction  has  taken  place.  The  yellow  precipitate  is 
more  likely  to  occur  if  the  urine  is  added  rapidly  and  in  large  amount,  whereas 
with  a  less  rapid  addition  of  smaller  amounts  of  urine  the  brownish-red  pre- 
cipitate is  generally  formed.  The  differences  in  color  of  the  cuprous  oxide  pre- 
cipitates under  different  conditions  are  apparently  due  to  differences  in  the 
size  of  the  particles,  the  more  finely  divided  precipitates  having  a  yellow 
color,  while  the  coarser  ones  are  red.  In  the  presence  of  protective  colloidal 
substances  the  yellow  precipitate  is  usually  formed.2 

This  is  a  much  more  satisfactory  test  than  Trommer's,  but  even 
this  test  is  not  entirely  reliable  when  used  to  detect  sugar  in  the  urine. 
Such  bodies  as  conjugate  glycuronates,  uric  acid,  nucleo protein,  and  homo- 
gentisic  acid,  when  present  in  sufficient  amount,  may  produce  a  result 
similar  to  that  porduced  by  sugar.  Phosphates  of  the  alkaline  earths 
may  be  precipitated  by  the  alkali  of  the  Fehling's  solution  and  in  appear- 
ance may  be  mistaken  for  the  cuprous  oxide.  Cupric  hydroxide 
may  also  be  reduced  to  cuprous  oxide  and  this  in  turn  be  dissolved  by 
creatinine,  a  normal  urinary  constituent.  This  will  give  the  urine  under 
examination  a  greenish  tinge  and  may  obscure  the  sugar  reaction  even 
when  a  considerable  amount  of  sugar  is  present.  According  to  Laird3 
even  small  amounts  of  creatinine  will  retard  the  reaction  velocity  of  re- 
ducing sugars  with  Fehling's  solution. 

Conjugate  glycuronates  are  formed  after  the  ingestion  of  such  sub- 
stances as  chloral  hydrate,  camphor,  menthol,  thymol,  antipyrin, 
phenol,  etc.  The  chloral  hydrate  is  excreted  in  the  urine  as  trichlor- 
ethylglycuronate,  CC13  CH2  OOC(CHOH)4  CHO.  This  compound  re- 
duces Fehling's  solution  and  is  /e^orotatory,  whereas  glucose  also 
reduces  but  is  dextrorotatory.  Therefore  by  means  of  a  polariscopic 
test  we  may  differentiate  between  a  "chloral  urine"  and  a  "sugar 
urine. " 

In  testing  urine  preserved  by  chloroform  a  positive  test  may  be  ob- 
tained in  the  absence  of  sugar.  This  is  due  to  the  fact  that  the  hot 
alkali  produces  formic  acid  (a  reducing  fatty  acid)  from  the  chloroform. 

Ammonium  salts  also  interfere  with  Fehling's  test.     If  present  in 

1  In  case  doubtful  results  are  obtained  by  this  test  owing  to  the  presence  of  interfering 
substances  the  urine  should  be  clarified  and  the  test  repeated.     To  clarify  the  urine  in- 
troduce 10  c.c.  into  a  test-tube,  add  i  gram  of  pure  blood  charcoal,  heat  to  boiling  and  allow 
to  stand  with  occasional  shaking  for  five  minutes.     Use  the  filtrate  in  the  test. 

2  Fischer  and  Hooker:  Science,  N.  S.  XLV,  505,  1917. 

3  Laird:  Journ.  Path,  and  Bact.,  16,  398,  1912. 


URINE  435 

excess  the  urine  should  be  made  alkaline  and  boiled  in  order  to  decom- 
pose the  ammonium  salts. 

(c)  Benedict's  Test.1 — Benedict  has  modified  the  Fehling  solution  and  has 
succeeded  in  obtaining  one  which  does  not  deteriorate  upon  long  standing.2 
The  following  is  the  procedure  for  the  detection  of  glucose  in  the  urine :  To  5  c.c. 
of  the  reagent  in  a  test-tube  add  8  (not  more)  drops  of  the  urine  to  be  examined. 
The  fluid  is  then  boiled  vigorously  for  from  one  to  two  minutes  and  then  allowed 
to  cool  spontaneously.     (Do  not  hasten  cooling  by  immersion  hi  cold  water.) 
In  the  presence  of  glucose  the  entire  body  of  the  solution  will  be  filled  with  a 
colloidal  precipitate,  which  may  be  red,  yellow,  or  green  hi  color,  depending 
upon  the  amount  of  sugar  present.     In  the  presence  of  over  0.2-0.3  per  cent 
of  glucose  the  precipitate  will  form  quickly.    If  no  glucose  is  present,  the  solution 
will  either  remain  perfectly  clear,  or  will  show  a  very  faint  turbidity,  due  to 
precipitated  urates. 

Even  very  small  quantities  of  glucose  in  urine  (o.i  per  cent) 
yield  precipitates  of  surprising  bulk  with  this*  reagent,  and  the  positive 
reaction  for  glucose  is  the  filling  of  the  entire  body  of  the  solution 
with  a  precipitate,  so  that  the  solution  becomes  opaque.  Since  amount 
rather  than  color  of  the  precipitate  is  made  the  basis  of  this  test,  it 
may  be  applied,  even  for  the  detection  of  small  quantities  of  glucose, 
as  readily  in  artificial  light  as  in  daylight.  Chloroform  does  not  in- 
terfere with  this  test  nor  do  uric  acid  or  creatinine  interfere  to  such 
an  extent  as  in  the  case  of  Fehling's  test. 

(d)  Folin-McEllroy  Test.3— To  5  c.c.  of  the  reagent4  in  a  test  tube  add  5-8 
drops  of  urine  (never  add  more  than  0.5  c.c.)  and  boil  for  1-2  minutes  or  heat  in  a 
beaker  of  boiling  water  for  3  minutes.    If  more  than  the  normal  traces  of  sugar 
be  present  the  hot  solution  will  be  filled  with  a  colloidal  (greenish-yellow  or 
reddish)  precipitate  as  in  Benedict's  test.    Because  of  the  sensitiveness  of  this 
test,  when  working  with  urine  only  a  distinctly  positive  test  obtained  with  the 
solution  still  hot  is  to  be  regarded  as  positive. 

1  Benedict:  Jour.  Biol.  Chem.,  5,  485,  1909:  Jour.  Am.  Med.  Ass'n,  57,  1193,  1911. 

2  Benedict's  new  solution  has  the  folio  wing  composition: 

Copper  sulphate 17.3  gm. 

Sodium  citrate 1 73 .  o  gm. 

Sodium  carbonate  (anhydrous) 100.0  gm 

Distilled  water  to 1000 .  o  c.c. 

With  the  aid  of  heat  dissolve  the  sodium  citrate  and  carbonate  in  about  800  c.c.  of  water 
Pour  (through  a  folded  filter  if  necessary)  into  a  glass  graduate  and  make  up  to  850  c.c. 
Dissolve  the  copper  sulphate  in  about  100  c.c.  of  water.  Pour  the  carbonate-citrate  solu- 
tion into  a  large  beaker  or  casserole  and  add  the  copper  sulphate  solution  slowly,  with 
constant  stirring  and  make  up  to  one  liter.  The  mixed  solution  is  ready  for  use,  and  does 
not  deteriorate  upon  long  standing. 

3Folin  and  McEllroy:  Jour.  Biol.  Chem.,  33,  513,  1918. 

4Folin-McEllroy  Reagent. — Dissolve  100  g.  of  sodium  pyrophosphate,  30  g.  of  diso- 
dium  phosphate  and  50  g.  of  dry  sodium  carbonate  in  approximately  i  liter  of  water  by 
the  aid  of  a  little  heat.  Dissolve  separately  13  g.  of  copper  sulphate  in  about  200  c.c.  of 
water.  Pour  the  copper  sulphate  solution  into  the  phosphate-carbonate  solution  and 
shake. 


436  PHYSIOLOGICAL  CHEMISTRY 

(e)  Haines'  Test. — This  is  a  copper  reduction  test  similar  in  many 
respects  to  the  Fehling  and  Benedict  reactions.     In  Haines'  solution1 
the  cupric  hydroxide  is  held  in  solution  by  glycerol  instead  of  Rochelle 
salt  as  in  Fehling's  solution. 

Perform  the  test  as  follows :  Introduce  about  5  c.c.  of  Haines'  solution1  into  a 
test-tube  and  heat  to  boiling.  If  no  reduction  occurs  add  6-8  drops  of  the  urine 
and  again  bring  to  a  boil.  If  glucose  is  present  an  abundant  yellow  or  brownish- 
red  cuprous  oxide  precipitate  is  thrown  down.  This  test  is  about  as  delicate  as 
Fehling's  test. 

(f)  Bismuth  Reduction  Test  (Nylander). — To  5  c.c.  of  urine  hi  a  test-tube 
add  one-tenth  its  volume  of  Nylander's  reagent2  and  heat  for  five  minutes 
in  a  boiling  water-bath.3    The  mixture  will  darken  if  reducing  sugar  is  present 
and  upon  standing  for  a  few  moments  a  black  color  will  appear. 

This  color  is  due  to  the  precipitation  of  bismuth.  If  the  test  is 
made  on  urine  containing  albumin  this  must  be  removed,  by  boiling 
and  filtering,  before  applying  the  test,  since  with  albumin  a  similar 
change  of  color  is  produced.  Glucose  when  present  to  the  extent  of 
0.08  per  cent  may  be  easily  detected  by  this  reaction  (Rabe4  claims  that 
o.oi  per  cent  may  be  so  detected).  Uric  acid,  creatinine  and  homo- 
gentisic  acid  which  interfere  with  the  Fehling  test  do  not  interfere  with 
the  Nylander's  reaction.  It  is  claimed  by  Bechold  that  the  bismuth 
reduction  tests  give  a  negative  reaction  with  solutions  containing 
sugar  when  mercuric  chloride  or  chloroform  is  present.  Other  ob- 
servers5 have  failed  to  verify  the  inhibitory  action  of  the  mercuric 
chloride  and  have  shown  that  the  inhibitory  influence  of  chloroform 
may  be  overcome  by  raising  the  temperature  of  the  urine  to  the  boiling- 
point  for  a  period  of  five  minutes  previous  to  making  the  test. 

Urines  rich  in  indican,  uroerythrin,  urcchrome  or  hematopcrphyrin, 
as  well  as  urines  excreted  after  the  ingestion  of  large  amounts  of  certain 
medicinal  substances,  may  give  a  darkening  of  the  Nylander's  reagent 
similar  to  that  of  a  true  sugar  reaction.  It  is  a  disputed  point  whether 
the  urine  after  the  administration  of  urotropin  will  reduce  the  Nylan- 
der reagent.6 

1  Haines  solution  may  be  prepared  by  dissolving  8.314  grams  of  copper  sulphate  in 
400  c.c.  of  water  adding  40  c.c.  of  glycerol  and  500  c.c.  of  5  per  cent  potassium  hydroxide 
solution. 

2  Nylander's  reagent  is  prepared  by  digesting  2  grams  of  bismuth  subnitrate  and  4  grams 
of  Rochelle  salt  in  100  c.c.  of  a  10  per  cent  potassium  hydroxide  solution.     The  reagent  is 
then  cooled  and  filtered. 

3  Hammarsten  suggests  that  the  solution  be  boiled  for  2-5  minutes  (according  to  the 
sugar  content). over  a  free  flame  and  the  tube  then  permitted  to  stand  five  minutes  before 
drawing  conclusions. 

4  Rabe:  Apoth.  Ztg.,  29,  554,  1914. 

5Rehfuss  and  Hawk:  Jour.  Biol.  Chem.,  7,  267,  1910;  also  Zeidlitz:  Upsala  LakSre- 
foren  Fork.,  N.  F.,  n,  1906. 

6Abt:  Archives  of  Pediatrics,  24,  275,  1907;  also  Weitbrecht:  Schweiz.  Woch.,  47,  577, 
1909. 


URINE  437 

Strausz1  has  recently  shown  that  the  urine  of  diabetics  to  whom 
"lothion"  (diiodohydroxypropane)  has  been  administered  will  give  a 
negative  Nylander's  reaction  and  respond  positively  to  the  Fehling  and 
polarization  tests.  "lothion"  also  interferes  with  the  Nylander  test 
in  vitro  whereas  KI  and  I  do  not. 

According  to  Rustin  and  Otto  the  addition  of  PtCl4  increases  the 
delicacy  of  Nylander's  reaction.  They  claim  that  this  procedure  causes 
the  sugar  to  be  converted  quantitatively.  No  quantitative  method  has 
yet  been  devised,  however,  based  upon  this  principle. 

A  positive  bismuth  reduction  test  is  probably  due  to  the  following 
reactions : 

0)  Bi(OH)2NO3  +  KOH  ->  Bi(OH)3+  KNO3. 

(b)  2Bi(OH)3-30  -»Bi2  +  3H20. 

Bohmansson,2  before  testing  the  urine  under  examination  treats  it 
(10  c.c.)  with  y$  volume  of  25  per  cent  hydroehloric  acid  and  J^  volume 
of  boneblack.  This  mixture  is  shaken  one  minute,  then  filtered, 
and  the  neutralized  nitrate  tested  by  Nylander's  reaction.  Bohmansson 
claims  that  this  procedure  removes  certain  interfering  substances, 
notably  urochrome. 

(g)  Indigo  Carmine  Test. — Place  in  a  test  tube  2  c.c.  of  water  with  an  indigo- 
sodium-carbonate  tablet  and  one  sodium  carbonate  tablet.  These  tablets  may 
be  obtained  from  Parke,  Davis  &  Company. 

Heat  the  tube  gently  until  the  indigo  is  cjissolved.  Add  to  the  blue  solution, 
from  a  pipette,  one  drop  of  the  urine  to  be  tested,  and  keep  the  fluid  at  the  boiling 
point,  without,  however,  permitting  active  boiling,  for  sixty  seconds. 

If  no  change  is  produced  add  a  second  drop  of  the  urine,  and  heat  once  more. 
If  any  notable  quantity  of  sugar  is  present,  the  fluid  will  be  observed  to  change 
from  pure  blue  to  violet,  then  to  purple  and  red,  and  in  extreme  cases  will  fade 
to  a  pale  yellow.  If  there  is  only  a  trace  of  sugar,  the  color  will  merely  change 
to  one  of  the  intermediate  shades. 

Care  should  be  exercised  to  prevent  agitation  or  boiling  of  the  liquid  during 
this  test.  Contact  with  oxygen  of  the  ah*  from  boiling  or  agitation  prevents  the 
discharge  of  the  blue  color. 

Normal  urine  itself  produces  a  reaction  if  added  in  sufficient  quantity,  5  to 
8  drops  generally  being  sufficient  to  change  the  color  to  purple  or  red.  If, 
however,  no  more  than  one  drop  of  the  urine  is  employed  in  the  test,  a  change 
in  color  is  proof  that  sugar  is  present  in  abnormal  quantity. 

3.  Fermentation  Test. — Rub  up  in  a  mortar  about  15  c.c.  of  the  urine  with  a 
small  piece  of  compressed  yeast.  Transfer  'the  mixture  to  a  saccharometer 
(Fig.  5,  page  30)  and  stand  it  aside  hi  a  warm  place  for  about  12  hours.  If  glu- 
cose is  present,  alcoholic  fermentation  will  occur  and  carbon  dioxide  will  collect 
as  a  gas  in  the  upper  portion  of  the  tube.  On  the  completion  of  fermentation, 
introduce,  by  means  of  a  bent  pipette,  a  little  KOH  solution  into  the  graduated 

1  Strausz:  Munch,  med.  Woch.,  59,  85,  1912. 
1  Bohmansson:  Biochem.  Zeit.,  19,  p.  281. 


438  PHYSIOLOGICAL   CHEMISTRY 

portion,  place  the  thumb  tightly  over  the  opening  in  the  apparatus  and  invert  the 
saccharometer.  Remembering  that  KOH  has  the  power  to  absorb  CO  a  how 
do  you  explain  the  result?1. 

Mathews2  suggests  an  easy  method  for  differentiation  and  estimation  of 
lactose  in  presence  of  glucose,  based  on  reduction  before  and  after  fermentation 
with  yeast. 

4.  Polariscopic  Examination. — For  directions  as  to  the  use  of  the  polariscope 
see  Chapter  II. 

PROTEINS 

Normal  urine  contains  a  trace  of  protein  material,  but  the  amount 
present  is  so  slight  as  to  escape  detection  by  any  of  the  simple  tests  in 
general  use  for  the  detection  of  protein  urinary  constituents.  The 
following  are  the  more  important  forms  of  protein  material  which  have 
been  detected  in  the  urine  under  pathological  conditions: 

(1)  Serum  albumin. 

(2)  Serum  globulin. 

Deutero-proteose. 


(3)  Proteoses 


Hetero-proteose. 


"Bence- Jones'  protein." 

(4)  Peptone. 

(5)  Nucleoprotein. 

(6)  Fibrin. 

(7)  Oxyhemoglobin. 

ALBUMIN 

Normal  urine  contains  a  trace  of  albumin  which  is  too  slight  to  be 
detected  by  the  usual  procedures. 

Albuminuria  is  a  condition  in  which  serum  albumin  or  serum  globulin 
appears  in  the  urine.  There  are  two  distinct  forms  of  albuminuria,  i.e., 
renal  albuminuria  and  accidental  albuminuria.  Sometimes  the  terms 
"true"  albuminuria  and  "false"  albuminuria  are  substituted  for  those 
just  given.  In  the  renal  type  the  albumin  is  excreted  by  the  kidneys. 
This  is  the  more  serious  form  of  the  malady  and  at  the  same  time  is  more 
frequently  encountered  than  the  accidental  type.  Among  the  causes  of 
renal  albuminuria  are  altered  blood  pressure  in  the  kidneys,  altered 
kidney  structure,  or  changes  in  the  composition  of  the  blood  entering 
the  kidneys,,  thus  allowing  the  albumin  to  diffuse  more  readily.  In  the 
accidental  form  of  albuminuria  the  albumin  is  not  excreted  by  the 

1  The  findings  of  Neuberg  and  associates  indicate  that  the  liberation  of  carbon  dioxide 
by  yeast  is  not  necessarily  a  criterion  of  the  presence  of  sugar.  The  presence  of  an  enzyme 
called  carboxylase  has  been  demonstrated  in  yeast  which  has  the  power  of  splitting  off  COi 
from  the  carboxyl  group  of  amino-  and  other  aliphatic  acids. 

2 Mathews:  Jour.  Am.  Med.  dss'n,  75,  1568,  1920. 


URINE  439 

kidneys  as  is  the  case  in  the  renal  form  of  the  disorder,  but  arises  from 
the  blood,  lymph,  or  some  albumin-containing  exudate  coming  into 
contact  with  the  urine  at  some  point  below  the  kidneys.  It  has  been 
suggested1  that  albuminurias  may  be  classed  as  pre-renal,  renal  and 
post-renal.  The  pre-renal  type  is  illustrated  by  the  albuminuria  of 
heart  disease,  whereas  the  post-renal  form  corresponds  to  what  we  have 
called  "accidental"  albuminuria. 

The  determination  of  albumin  may  be  of  assistance  in  following  the 
course  of  kidney  disturbances,  but  the  results  can  only  be  interpreted 
in  the  light  of  other  clinical  findings. 

EXPERIMENTS 
(The  urine  should  be  filtered  before  performing  these  tests.) 

Nitric  Acid  Ring  Test  (Heller).— Place  5  c.c.  of  concentrated  HNO3  in  a  test- 
tube,  incline  the  tube,  and  by  means  of  a  pipette  allow  the  urine  to  flow  slowly 
down  the  side.  The  liquids  should  stratify  with  the  formation  of  a  white  zone 
of  precipitated  albumin  at  the  point  of  juncture. 

If  the  albumin  is  present  in  very  small  amount  the  white  zone  may 
not  form  until  the  tube  has  been  allowed  to  stand  for  several  minutes. 
If  the  urine  is  quite  concentrated  a  white  zone,  due  to  uric  acid  or  urates, 
will  form  upon  treatment  with  nitric  acid  as  indicated.  This  ring  may 
be  easily  differentiated  from  the  albumin  ring  by  repeating  the  test 
after  diluting  the  urine  with  3  or  4  volumes  of  water,  whereupon  the 
ring,  if  due  to  uric  acid  or  urates,  will  not  appear.  It  is  ordinarily 
possible  to  differentiate  between  the  albumin  ring  and  the  uric  acid  ring 
without  diluting  the  urine,  since  the  ring,  when  due  to  uric  acid,  has 
ordinarily  a  less  sharply  defined  upper  border,  is  generally  broader  than 
the  albumin  ring  and  frequently  is  situated  in  the  urine  above  the  point 
of  contact  with  the  nitric  acid.  Concentrated  urines  also  occasionally 
exhibit  the  formation,  at  the  point  of  contact,  of  a  crystalline  ring  with 
very  sharply  defined  borders.  This  is  urea  nitrate  and  is  easily  dis- 
tinguished from  the  "fluffy"  ring  of  albumin.  If  there  is  any  diffi- 
culty in  differentiation  a  simple  dilution  of  the  urine  with  water,  as 
above  described,  will  remove  the  difficulty.  Various  colored  zones,  due 
either  to  the  presence  of  indican,  bile  pigments,  or  to  the  oxidation  of 
other  organic  urinary  constituents,  may  form  in  this  test  under  certain 
conditions.  These  colored  rings  should  never  be  confounded  with  the 
white  ring  which  alone  denotes  the  presence  of  albumin. 

After  the  administration  of  certain  drugs  a  white  precipitate  of 
resin  acids  may  form  at  the  point  of  contact  of  the  two  fluids  and  may 

1  Bruce:  Lancet,  May  6,  1911,  p.  1205. 


440  PHYSIOLOGICAL  CHEMISTRY 

cause  the  observer  to  draw  wrong  conclusions.  This  ring,  if  composed 
of  resin  acids,  will  dissolve  in  alcohol,  whereas  the  albumin  ring  wiH  not 
dissolve  in  this  solvent. 

Weinberger  has  shown  that  a  ring  closely  resembling  the  albumin 
ring  is  often  obtained  in  urines  preserved  for  a  considerable  time  by 
thymol  when  subjected  to  the  nitric  acid  test.  The  ring  is  due  to  the 
formation  of  nitrosothymol  and  possibly  nitrothymol.  If  the  thymol 
is  removed  from  the.  urine  by  extraction  with  petroleum  ether1  previous 
to  adding  nitric  acid,  the  ring  does  not  form. 

An  instrument  called  the  albumoscope  (horismascope)  has  been  de- 
vised for  use  in  this  test  and  has  met  with  considerable  favor.  The 
method  of  using  the  albumoscope  is  described  below. 

Use  of  the  Albumoscope. — This  instrument  is  intended  to  facilitate 
the  making  of  "ring"  tests  such  as  Heller's  and  Roberts'.  In  making 
a  test  about  5  c.c.  of  the  solution  under  examination  is  first  intro- 
duced into  the  apparatus  through  the  larger  arm  (see  Fig.  135), 
and  the  reagent  used  in  the  particular  test  is  then  introduced  through 
the  capillary  arm  and  allowed  to  flow  down  underneath  the  solution 
under  examination.  If  a  reasonable  amount  of  care  is  taken  there  is 
no  possibility  of  mixing  the  two  solutions  and  a  defi- 
nitely defined  white  "ring"  is  easily  obtained  at  the 
zone  of  contact. 

2.  Nitric  Acid  and  Magnesium  Sulphate  Ring  Test* 
(Roberts). — Place  5  c.c.  of  Roberts'  reagent2  in  a  test- 
tube,  incline  the  tube,  and  by  means  of  a  pipette  allow  the 
urine  to  flow  slowly  down  the  side.  The  liquids  should 
stratify  with  the  formation  of  a  white  zone  of  precipitated 
albumin  at  the  point  of  juncture. 

This  test  is  a  modification  of  Heller's  ring  test 
and  is  rather  more  satisfactory  than  that  test,  since 
the  colored  rings  never  form  and  the  consequent 
FIG.    135.— ALBUMO-  confusion  is  avoided.     The  albumoscope  (see  above) 
may  also  be  used  in  making  this  test. 

3.  Spiegler's  Ring  Test— Place  5.  c.c.  of  Spiegler's  reagent3  in  a  test-tube,  in- 

^ 1  Accomplished  readily  by  gently  agitating  equal  volumes  of  petroleum  ether  and  the 
urine  under  examination  for  two  minutes  in  a  test-tube  before  applying  the  test. 

8  Roberts'  reagent  is  composed  of  i  volume  of  concentrated  HNO3  and  5  volumes  of  a 
saturated  solution  of  MgSO4. 

3  Spieglers'  reagent  has  the  following  composition: 

Tartaric  acid 2O  grams. 

Mercuric  chloride 40  grams. 

Sodium  chloride 5o  grams! 

Glycerol I00  grams. 

Distilled  water , I00o  grams. 


URINE  441 

cline  the  tube  and,  by  means  of  a  pipette,  allow  5  c.c.  of  urine,  acidified  with  acetic 
acid,  to  flow  slowly  down  the  side.  *A  white  zone  will  form  at  the  point  of  contact. 
This  is  an  exceedingly  delicate  test,  in  fact  too  delicate  for  ordinary  clinical  purposes, 
since  it  serves  to  detect  albumin  when  present  in  the  merest  trace  (1:250,000)  and 
hence  most  normal  urines  will  give  a  positive  reaction  for  albumin  when  this  test  is 
applied.  Proteose  and  peptone  are  also  said  to  respond  to  this  test. 

4.  Coagulation  or  Boiling  Test. — (a)  Heat  5  c.c.  of  urine  to  boiling  in  a  test- 
tube.     (If  the  urine  is  not  clear  it  should  be  filtered.)    A  precipitate  forming  at 
this  point  is  due  either  to  albumin  or  to  phosphates.    Acidify  the  urine  slightly 
by  the  addition  of  3-5  drops  of  very  dilute  acetic  acid,  adding  the  acid  drop  by 
drop  to  the  hot  solution.    If  the  precipitate  is  due  to  phosphates  it  will  disappear 
under  these  conditions,  whereas  if  it  is  due  to  albumin  it  will  not  only  fail  to 
disappear  but  will  become  more  flocculent  in  character,  since  the  reaction  of  a 
fluid  must  be  acid  to  secure  the  complete  precipitation  of  the  albumin  by  this 
coagulation  process. 

Too  much  acid  should  be  avoided  since  it  will  cause  the  albumin  to 
go  into  solution.  Certain  resin  acids  may  be  precipitated  by  the 
acid,  but  the  precipitate  due  to  this  cause  may  be  easily  differentiated 
from  the  albumin  precipitate  by  reason  of  its  solubility  in  alcohol. 

(b)  A  modification  of  this  test  in  quite  general  use  is  as  follows :  Fill  a  test- 
tube  two-thirds  full  of  urine  and  gentry  heat  the  upper  half  of  the  fluid  to  boiling, 
being  careful  that  this  fluid  does  not  mix  with  the  lower  hah*.  A  turbidity  indi- 
cates albumin  or  phosphates.  Acidify  the  urine  slightly  by  the  addition  of  3-5 
drops  of  dilute  acetic  acid,  when  the  turbidity,  if  due  to  phosphates,  will  disappear. 

Nitric  acid  is  often  used  in  place  of  acetic  acid  in  these  tests.  In 
case  nitric  acid  is  used  ordinarily  1-2  drops  is  sufficient. 

5.  Acetic  Acid  and  Potassium  Ferrocyanide  Test. — To  5  c.c.  of  urine  in  a 
test-tube  add  5-10  drops  of  acetic  acid.    Mix  well  and  add  potassium  ferro- 
cyanide  drop  by  drop,  until  a  precipitate  forms. 

This  is  a  very  delicate  test.  Schmiedl  claims  that  a  precipitate  of 
K2ZnFe(CN)e  or  Zn2Fe(CN)e  is  formed  when  urines  containing  zinc 
are  subjected  to  this  test  and  that  this  precipitate  resembles  the 
precipitate  secured  with  protein  solutions.  In  the  case  of  human 
urine  a  reaction  was  obtained  when  0.000022  gram  of  zinc  per  cubic 
centimeter  was  present.  Schmiedl  further  found  that  the  urine  col- 
lected from  rabbits  housed  in  zinc-lined  cages  possessed  a  zinc  content 
which  was  sufficient  to  yield  a  ready  response  to  the  test. 

Proteoses  may  also  be  detected  by  this .  test.  To  differentiate 
albumin  from  proteose  perform  the  coagulation  test  (see  above). 

GLOBULIN 

Serum  globulin  is  not  a  constituent  of  normal  urine  but  frequently 
occurs  in  the  urine  under  pathological  conditions  and  is  ordinarily 


442  PHYSIOLOGICAL   CHEMISTRY 

associated  with  serum  albumin.  In  albuminuria  globulin  in  varying 
amounts  often  accompanies  the  albumin,  and  the  clinical  significance 
of  the  two  is  very  similar.  Under  certain  conditions  globulin  may  occur 
in  the  urine  unaccompanied  by  albumin. 

EXPERIMENTS 

Globulin  will  respond  to  all  the  tests  just  outlined  under  Albumin. 
If  it  is  desirable  to  differentiate  between  albumin  and  globulin  in  any 
urine  the  following  processes  may  be  employed: 

1.  Saturation  with  Magnesium  Sulphate. — Place  25  c.c.  of  neutral  urine  hi 
a  small  beaker  and  add  pulverized  magnesium  sulphate  in  substance  to  the  point 
of  saturation.    If  the  protein  present  is  globulin  it  will  precipitate  at  this  point. 
If  no  precipitate  is  produced  acidify  the  saturated  solution  with  acetic  acid  and 
warm  gentry.    Albumin  will  be  precipitated  if  present. 

The  above  procedure  may  be  used  to  separate  globulin  and  albumin 
if  present  in  the  same  urine.  To  do  this  filter  off  the  globulin  after  it 
has  been  precipitated  by  the  magnesium  sulphate,  then  acidify  the  clear 
solution  and  warm  gently  as  directed.  Note  the  formation  of  the 
albumin  precipitate. 

2.  Half -saturation  with  Ammonium  Sulphate. — Place  25  c.c.  of  neutral  urine 
in  a  small  beaker  and  add  an  equal  volume  of  a  saturated  solution  of  ammonium 
sulphate.     Globulin,  if  present,  will  be  precipitated.    If  no  precipitate  forms  add 
ammonium  sulphate  in  substance  to  the  point  of  saturation.     If  albumin  is  present 
it  will  be  precipitated  upon  saturation  of  the  solution  as  just  indicated.    This 
method  may  also  be  used  to  separate  globulin  and  albumin  when  they  occur  in  the 
same  urine. 

Frequently  in  urine  which  contains  a  large  amount  of  urates  a  precipitate  of 
ammonium  urate  may  occur  when  the  ammonium  sulphate  solution  is  added  to  the 
urine.  This  urate  precipitate  should  not  be  confounded  with  the  precipitate  due 
to  globulin.  The  two  precipitates  may  be  differentiated  by  means  of  the  fact  that 
the  urate  precipitate  ordinarily  appears  only  after  the  lapse  of  several  minutes 
whereas  the  globulin  generally  precipitates  at  once. 

PROTEOSE  AND  PEPTONE 

Proteoses,  particularly  deutero-proteose  and  hetero-proteose,  have 
frequently  been  found  in  the  urine  under  various  pathological  con- 
ditions, such  as  diphtheria,  pneumonia,  intestinal  ulcer,  carcinoma, 
dermatitis,  osteomalacia,  atrophy  of  the  kidneys,  and  in  sarcomata 
of  the  bones  -of  the  trunk.  The  presence  of  proteose  in  the  urine  may 
frequently  be  demonstrated  in  any  pathological  condition  in  which  there 
is  absorption  of  partially  digested  pus.  "Bence- Jones'  protein,"  a 
proteose-like  substance,  is  of  interest  in  this  connection  and  its  appear- 
ance in  the  urine  is  believed  to  be  of  great  diagnostic  importance  in 


URINE  443 

cases  of  multiple  myeloma  or  myelogenic  osteosarcoma.  By  some  in- 
vestigators this  protein  is  held  to  be  a  variety  of  hetero-proteose,  whereas 
others  claim  that  it  possesses  albumin  characteristics.  The  origin  o 
"Bence- Jones'  protein"  is  unknown.  Its  origin  has  at  various  time 
been  ascribed  to  the  blood  proteins,  the  bones  or  to  abnormal  metab-S 
lism  of  protein  material  in  the  body.  It  occurs  in  the  urine  in  about 
80  per  cent  of  the  cases  of  multiple  myeloma.  If  its  presence  is  unac- 
companied by  multiple  myeloma  it  is  nearly  always  associated  with 
some  disease  of  the  blood-forming  organs  or  of  the  bones.  When 
"Bence- Jones' protein"  is  hydrolyzed  it  is  found  to  contain  all  the 
aminoacids  which  are  characteristic  of  typical  proteins. 

Peptone  certainly  occurs  much  less  frequently  as  a  constituent  of 
the  urine  than  does  proteose,  in  fact  most  investigators  seriously  ques- 
tion its  presence  under  any  conditions.  There  are  many  instances 
of  peptonuria  cited  in  the  early  literature,  but  because  of  the  uncertainty 
in  the  conception  of  what  really  constituted  a  peptone  it  is  probable  that 
in  many  cases  of  so-called  peptonuria  the  protein  present  was  really 
proteose. 

EXPERIMENTS 

1.  Phosphotungstic  Precipitation  Test  (v.  Aldor). — Acidify  10  c.c.  of  urine 
with  hydrochloric  acid,  add  phosphotungstic  acid  until  no  more  precipitate  forms 
and  centrifugate1  the  solution.    Decant  the  supernatant  fluid,  add  some  abso- 
lute alcohol  to  the  precipitate,  and  centrifugate  again.    This  washing  with  alcohol 
is  intended  to  remove  the  urobilin  and  hence  should  be  continued  so  long  as  the 
alcohol  exhibits  any  coloration  whatever.    Now  suspend  the  precipitate  in  water 
and  add  potassium  hydroxide  to  bring  it  into  solution.    At  this  point  the  solution 
may  be  blue  in  color,  in  which  case  decolorization  may  be  secured  by  gently 
heating.    Apply  the  biuret  test  to  the  cool  solution.    A  positive  biuret  test  indi- 
cates the  presence  of  proteoses. 

2.  Boiling  Test. — Make  the  ordinary  coagulation  test  according  to  the  di- 
rection given  under  Albumin,  page  441.     If  no  coagulable  protein  is  found  allow 
the  boiled  urine  to  stand  and  note  the  gradual  appearance,  in  the  cooled  fluid,  of 
a  flaky  precipitate  of  proteose.     Spiegler's  reaction  may  also  be  applied  at  this 
point.     A  precipitate  indicates  proteose. 

3.  Schulte's  Method. — Acidify  50  c.c.  of  urine  with  dilute  acetic  acid  and  filter 
off  any  precipitate  of  nucleoprotein  which  may  form.     Now  test  a  few  cubic  centi- 
meters of  the  urine  for  coagulable  protein,  by  tests  2  and  4  under  Albumin,  page 
440.    If  coagulable  protein  is  present  remove  it  by  coagulation  and  filtration 
before  proceeding.    Introduce  25  c.c.  of  the  urine,  freed  from  coagulable  protein, 
into  150  c.c.  of  absolute  alcohol  and  allow  it  to  stand  for  12-24  hours.    Decant  the 
supernatant  fluid  and  dissolve  the  precipitate  in  a  smali, amount  of  hot  water.    Now 

1  If  not  convenient  to  use  a  centrifuge  the  precipitate  may  be  filtered  off  and  washed  on 
the  filter  paper  with  alcohol. 


444  PHYSIOLOGICAL  CHEMISTRY 

filter  this  solution,  and  after  testing  again  for  nucleoprotein  with  very  dilute  acetic- 
acid,  try  the  biuret  test.  If  this  test  is  positive  the  presence  of  proteose  is  indicated.1 

Urobilin  does  not  ordinarily  interfere  with  this  test  since  it  is  almost  entirely 
dissolved  by  the  absolute  alcohol  when  the  proteose  is  precipitated. 

4.  Detection  of  "Bence-Jones*  Protein." — Heat  the  suspected  urine  very 
gently,  carefully  noting  the  temperature.  At  as  low  a  temperature  as  4o°C.  a 
turbidity  may  be  observed,  and  as  the  temperature  is  raised  to  about  6o°C.  a 
flocculent  precipitate  forms  and  clings  to  the  sides  of  the  test-tube.  If  the  urine 
is  now  acidified  very  slightly  with  acetic  acid  and  the  temperature  further  raised 
to  ioo°C.  the  precipitate  at  least  partly  disappears;  it  will  return  upon  cooling 
the  tube. 

This  property  of  precipitating  at  so  low  a  temperature  and  of  dissolving  at  a 
higher  temperature  is  typical  of  "Bence- Jones'  protein"  and  may  be  used  to  differ- 
entiate it  from  all  other  forms  of  protein  material  occurring  in  the  urine. 


NUCLEOPROTEIN 

There  has  been  considerable  controversy  as  to  the  proper  classifica- 
tion for  the  protein  body  which  forms  the  "nubecula"  of  normal  urine. 
By  different  investigators  it  has  been  called  mucin,  mucoid,  phospho- 
protein,  nucleoalbumin,  and  nucleoprotein.  Of  course,  according  to 
the  modern  acceptation  of  the  meanings  of  these  terms  they  cannot  be 
synonymous.  Mucin  and  mucoid  are  glycoproteins  and  hence  contain 
no  phosphorus  (see  page  in),  whereas  phosphoproteins  and  nucleo- 
proteins  are  phosphorized  bodies.  It  may  possibly  be  that  both  these 
forms  of  protein,  i.e.,  the  glycopr-otein  and  the  phosphorized  type, 
occur  in  the  urine  under  certain  conditions  (see  page  413).  In  this 
connection  we  will  use  the  term  nucleoprotein.  The  pathological  con- 
ditions under  which  the  content  of  nucleoprotein  is  increased  includes 
all  affections  of  the  urinary  passages  and  in  particular  pyelitis,  nephritis, 
and  inflammation  of  the  bladder. 

EXPERIMENTS 

1.  Detection  of  Nucleoprotein. — Place  10  c.c.  of  urine  in  a  small  beaker, 
dilute  it  with  three  volumes  of  water  to  prevent  precipitation  of  urates,  and  make 
the  reaction  very  strongly  acid  with  acetic  acid.    If  the  urine  becomes  turbid 
it  is  an  indication  that  nucleoprotein  is  present. 

If  the  urine  under  examination  contains  albumin  the  greater  portion  of  this 
substance  should  be  removed  by  boiling  the  urine  before  testing  it  for  the  pres- 
ence of  nucleoprotein. 

2.  Tannic  Acid  Precipitation  Test  (Ott).— Mix  25  c.c.  of  the  urine  with 
an  equal  volume  of  a  saturated  solution  of  sodium  chloride  and  slowly  add 

1  If  it  is  considered  desirable  to  test  for  peptone  the  proteose  may  be  removed  by  satu- 
ration with  (NH4)2SO4  according  to  the  directions  given  on  p.  119  and  the  filtrate  tested 
for  peptone  by  the  biuret  test. 


URINE  445 

Almen's  reagent.1    In  the  presence  of  nucleoprotein  a  voluminous  precipitate 
forms. 

BLOOD 

The  pathological  conditions  in  which  blood  occurs  in  the  urine  may 
be  classified  under  the  two  divisions  hematuria  and  hemoglobinuria. 
In  hematuria  we  are  able  to  detect  not  only  the  hemoglobin  but  the 
unruptured  corpuscles  as  well,  whereas  in  hemoglobinuria  the  pig- 
ment alone  is  present.  Hematuria  is  brought  about  through  blood 
passing  into  the  urine  because  of  some  lesion  of  the  kidney  or  of  the 
urinary  tract  below  the  kidney.  Hemoglobinuria  is  brought  about 
through  hemolysis,  i.e.,  the  rupturing  of  the  stroma  of  the  erythrocyte 
and  the  liberation  of  the  hemoglobin.  This  may  occur  in  scurvy, 
typhus,  pyemia,  purpura,  and  in  other  diseases.  It  may  also  occur  as 
the  result  of  a  burn  covering  a  considerable  area  of  the  body,  or  may 
be  brought  about  through  the  action  of  cerjtain  poisons  or  by  the  in- 
jection of  various  substances  having  the  power  of  dissolving  the 
erythrocytes.  Transfusion  of  blood  may  also  cause  hemoglobinuria. 

Even  in  true  hematuria  the  erythrocytes  may  escape  detection  if 
the  urine  is  ammoniacal  inasmuch  as  the  cells  disintegrate  under  these 
conditions. 

EXPERIMENTS 

i.  Benzidine  Reaction. — This  is  orue  of  the  most  delicate  of  the  reac- 
tions for  the  detection  of  blood.  Different  benzidine  preparations  vary 
greatly  in  their  sensitiveness,  however.  Inasmuch  as  benzidine  solu- 
tions change  readily  upon  contact  with  light,  it  is  essential  that  they 
be  kept  in  a  dark  place. 

The  test  is  performed  as  follows:  To  a  saturated  solution  of  benzidine  in 
alcohol  or  glacial  acetic  acid  add  an  equal  volume  of  3  per  cent  hydrogen  peroxide 
and  i  c.c.  of  the  urine  under  examination.  If  the  mixture  is  not  already  acid, 
render  it  so  with  acetic  acid,  and  note  the  appearance  of  a  blue  color.  A 
control  test  should  be  made  substituting  water  for  the  urine. 

Often  when  urines  containing  a  small  amount  of  blood  are  tested  by 
this  reaction,  the  mixture  is  rendered  so  turbid  as  to  make  it  difficult  to 
decide  as  to  the  presence  of  a  faint  green  color.  The  sensitiveness 
of  the  benzidine  reaction  is  greater  when  applied  to  aqueous  solutions 
than  when  applied  to  the  urine. 

For  a  modification  of  this  test  and  further  discussion  see  Chapter 
XV  on  Blood  and  Lymph. 

1  Dissolve  5  grains  of  tannic  acid  in  240  c.c.  of  50  per  cent  alcohol  and  add  10  c.c.  of  25 
per  cent  acetic  acid. 


446  PHYSIOLOGICAL  CHEMISTRY 

2.  Guaiac  Test. — Place  5  c.c.  of  urine1  in  a  test-tube  and  by  means  of  a 
pipette  introduce  a  freshly  prepared  alcoholic  solution  of  guaiac  (strength  about 
i  :6o)  or  the  Lyle-Curtman2  guaiac  reagent  (see  p.  237)  into  the  fluid  until  a 
turbidity  results,  then  add  old  turpentine  or  hydrogen  peroxide,  drop  by  drop, 
until  a  blue  color  is  obtained. 

This  is  a  very  delicate  test  when  properly  performed.  Buckmaster 
has  suggested  the  use  of  guaiaconic  acid  instead  of  the  solution  of 
guaiac.  The  test  is  positive  both  before  and  after  boiling  the  blood 
for  15-20  seconds.  Pus  does  not  respond  after  boiling.  Old,  partly 
putrefied  pus  gives  the  test  even  without  the  addition  of  hydrogen 
peroxide  or  old  turpentine  whereas  fresh  pus  responds  upon  the  addition 
of  hydrogen  peroxide.  See  discussion  on  page  261  and  test  on  page  265. 

3.  Teichmann's  Heroin  Test. — Place  a  small  drop  of  the  suspected  urine  or  a 
small  amount  of  the  moist  sediment  on  a  microscopic  slide,  add  a  minute  grain 
of  sodium  chloride  and  carefully  evaporate  to  dryness  over  a  low  flame.    Put  a 
cover-glass  in  place,  run  underneath  it  a  drop  of  glacial  acetic  acid,  and  warm 
gently  until  the  formation  of  gas  bubbles  is  observed.    Cool  the  preparation, 
examine  under  the  microscope,  and  compare  the  form  of  the  crystals  with  those 
reproduced  in  Figs.  84  and  85,  page  268.     (See  Nippe's  modification,  page  267.) 

4.  Ortho-Tolidin  Test  (Ruttan  and  Hardisty).3— To  i  c.c.  of  a  4  per  cent 
glacial  acetic  acid  solution  of  o-tolidin4  in  a  test-tube  add  i  c.c.  of  the  solution 
under  examination  and  i  c.c.  of  3  per  cent  hydrogen  peroxide.    In  the  presence 
of  blood  a  bluish  color  develops  (sometimes  rather  slowly)  and  persists  for  some- 
time (several  hours  in  some  instances). 

This  test  is  said  to  be  as  sensitive  for  the  detection  of  occult  blood 
in  feces  and  stomach  contents  as  is  the  benzidine  reaction.  It  is  also 
cl  imed  to  be  more  satisfactory  for  urine  than  any  other  blood  test. 
The  acetic  acid  solution  may  be  kept  for  one  month  with  no  reduction 
in  delicacy. 

5.  Spectroscopic  Examination. — Submit  the  urine  to  a  spectroscopic  exami- 
nation according  to  the  directions  given  on  page  300,  looking  especially  for  the 
absorption  bands  of  oxyhemoglobin  and  methemoglobin  (see  Absorption  Spectra, 
Plate  I). 

6.  Potassium  Hydroxide  Test  (Heller). — Render  10  c.c.  of  urine  strongly  alka- 
line with  potassium  hydroxide  solution  and  heat  to  boiling.    Upon  allowing  the 
heated  urine  to  stand  a  precipitate  of  phosphates,  colored  red  by  the  contained 

1  Alkaline  urine  should  be  made  slightly  acid  with  acetic  acid  as  the  blue  end-reaction 
is  very  sensitive  to  alkali. 

2Lyle  and  Curtman:  Jour.  Biol.  Chem.,  33,  i,  1918. 

3  Ruttan  and  Hardisty:  Canadian  Medical  Assn.  Journal,  Nov.,  1912,  also  Biochemical 
Bull.,  2,  225,  1913. 

4NH2  NH2 

C6H4-C6H4 
CH3  CH8 


URINE  447 

hematin,  is  formed.    It  is  ordinarily  well  to  make  a  "control"  experiment  using 
normal  urine,  before  coming  to  a  final  decision. 

Certain  substances,  such  as  cascara  sagrada,  rhubarb,  santonin,  and  senna, 
cause  the  urine  to  give  a  similar  reaction.  Reactions  due  to  such  substances 
may  be  differentiated  from  the  true  blood  reaction  by  the  fact  that  both  the  pre- 
cipitate and  the  pigment  of  the  former  reaction  disappear  when  treated  with 
acetic  acid,  whereas  if  the-  color  is  due  to  hematin  the  acid  will  only  dissolve  the 
precipitate  of  phosphates  and  leave  the  pigment  undissolved. 

PUS 

Pus  may  be  present  in  the  urine  in  inflammatory  affections  of 
various  types.  Such  a  condition  is  termed  pyuria.  Albumin  always 
accompanies  the  pus.  In  catarrh  of  the  bladder  and  in  inflammation 
of  the  urethra  or  of  the  pelvis  of  the  kidney  pus  is  particularly  apt  to 
be  present  in  the  urine.  If  a  urine  of  high  pus  concentration  is  voided 
it  may  indicate  the  rupturing  of  an  abscess  in  some  part  of  the  genito- 
urinary tract.  Pus  may  be, detected  by  one*  of  the  procedures  given 
below. 

EXPERIMENTS 

1.  Microscopical  Detection  of  Pus. — The  characteristic  form  elements  of  pus  are 
leucocytes.    They  may  occur  in  very  small  number  in  normal  urine.     Examine  the 
urine  (centrifugated  if  necessary)  under  the  microscope.    Any  considerable  number 
of  pus  corpuscles  indicates  a  pathological  urine.     In  acid  urine  the  pus  corpuscles 
appear  as  round,  colorless  cells,  composed  of  refractive,  granular  protoplasm. 
Sometimes  they  may  exhibit  amoeboid  movements,  particularly  if  the  slide  contain- 
ing them  be  warmed  slightly.     They  are  nucleated  (one  or  more  nuclei) ,  the  nuclei 
being  clearly  visible  only  upon  treating  the  cells  with  water,  acetic  acid  or  some 
other  suitable  reagent.     In  alkaline  urine  the  pus  corpuscles  are  often  degenerated. 
They  may  occur  as  swollen,  transparent  cells,  which  exhibit  no  granular  structure. 
If  the  degeneration  has  proceeded  far  enough  the  nuclei  fade  and  the  cell  disinte- 
grates and  only  debris  remains. 

Sometimes  it  is  almost  impossible  to  differentiate  between  pus  corpuscles  and 
certain  types  of  epithelial  cells.  In  such  a  case  apply  one  of  the  following  chemical 
tests. 

2.  Guaiac  Test.— This  test  is  not  specific  for  pus,  but  is  given  by  certain 
other  substances  and  particularly  by  blood  (see  Chapter  XV).    Perform  the  test 
as  follows:  Acidify  the  urine  (if  alkaline)  with  acetic  acid,  filter,1  and  add  tinc- 
ture of  guaiac  or  the  Lyle-Curtman2  guaiac  reagent  (p.  237)  to  the  sediment  on 
the  paper.    If  the  pus  is  old,  and  partly  putrefied  it  will  give  a  blue  color.     If 
no  blue  color  is  secured,  add  old  turpentine,  or  hydrogen  peroxide,  drop  by  drop. 
A  blue  color  formed  only  under  these  conditions  indicates  fresh  pus. 

As  a  control  test  boil  some  of  the  urine  (or  sediment)  for  15-20  seconds  and 
repeat  the  test.  Pus  does  not  respond  after  boiling.  In  the  case  of  blood  the 
test  is  positive  both  before  and  after  boiling. 

i  If  desired,  the  urine  may  be  centrifuged  and  the  sediment  used  in  the  test. 
2Lyle  and  Curtman:  Jour.  Biol.  Chem.,  33,  i,  1918. 


448  PHYSIOLOGICAL  CHEMISTRY 

3.  Potassium  Hydroxide  Test  (Donne). — Separate  the  sediment  from  the 
urine  (by  decantation,  filtration  or  centrifugation) ;  place  a  small  piece  of  solid 
potassium  hydroxide  on  the  sediment  and  stir.  If  pus  is  present  (and  particu- 
larly H  it  be  fresh  pus  and  not  disintegrated)  the  sediment  will  become  slimy  and 
tough.  If  the  sediment  is  mucus  it  will  more  or  less  pass  into  solution  in  the 
concentrated  alkali. 

BILE 

Both  the  pigments  and  the  acids  of  the  bile  may  be  detected  in  the 
urine  under  certain  pathological  conditions.  Of  the  pigments,  bilirubin 
is  the  only  one  which  has  been  positively  identified  in  fresh  urine;  the 
other  pigments,  when  present,  are  probably  derived  from  the  bilirubin. 
A  urine  containing  bile  may  be  yellowish-green  to  brown  in  color  and 
when  shaken  foams  readily.  The  staining  of  the  various  tissues  of  the 
body  through  the  absorption  of  bile  due  to  occlusion  of  the  bile  duct 
is  a  prominent  symptom  of  the  condition  known  as  icterus  or  jaundice. 
Bile  is  always  present  in  the  urine  under  such  conditions  unless  the 
amount  of  bile  reaching  the  tissues  is  extremely  small. 

EXPERIMENTS 
Tests  for  Bile  Pigments 

Practically  all  of  these  tests  for  bile  pigments  are  based  on  the 
oxidation  of  the  pigment  by  a  variety  of  reagents  with  the  formation 
of  a  series  of  colored  derivatives,  e.g.,  biliverdin  (green),  bilicyanin 
(blue),  choletelin  (yellow). 

1.  Gmelin's  Test. — To  about  5  c.c.  of  concentrated  nitric  acid  hi  a  test-tube 
add  an  equal  volume  of  urine  carefully  so  that  the  two  fluids  do  not  mix.    At  the 
point  of  contact  note  the  various  colored  rings ;  green,  blue,  violet,  red,  and  red- 
dish-yellow. 

2.  Rosenbach's  Modification  of  Gmelin's  Test. — Filter  5  c.c.  of  urine  through 
a  small  filter  paper.    Introduce  a  drop  of  concentrated  nitric  acid  into  the  cone 
of  the  paper  and  observe  the  succession  of  colors  as  given  hi  Gmelin's  test. 

3.  Huppert-Cole  Test.1— Boil  about  15  c.c.  of  the  fluid  in  a  test  tube.    Add 
two  drops  of  a  saturated  solution  of  magnesium  sulphate,  then  add  a  10  per  cent 
solution  of  barium  chloride,  drop  by  drop,  boiling  between  each  addition.    Con- 
tinue to  add  the  barium  chloride  until  no  further  precipitate  is  obtained.    Allow 
the  tube  to  stand  for  a  minute.     Pour  off  the  supernatant  fluid  as  cleanly  as 
possible  or  use  a  centrifuge.    To  the  precipitate  add  3  to  5  c.c.  of  97  per  cent 
alcohol,  two  drops  of  strong  sulphuric  acid,  and  two  drops  of  a  5  per  cent  aqueous 
solution  of  potassium  chlorate.    Boil  for  half  a  minute  and  allow  the  barium 
sulphate  to  settle.    The  presence  of  bile  pigments  is  indicated  by  the  alcohol 
solution  being-  colored  a  greenish  blue. 

NOTES. — To  render  the  test  more  delicate,  pour  off  the  alcoholic  solution  from 
the  barium  sulphate  into  a  dry  tube.     Add  about  one-third  its  volume  of  chloro- 
1  Cole's  "Practical  Physiological  Chemistry"  6th  Edition,  p.  268,  1920. 


URINE  449 

form  and  mix.  To  the  solution  add  about  an  equal  volume  of  water,  place  the 
thumb  on  the  tube,  invert  once  or  twice  and  allow  the  chloroform  to  separate. 
It  contains  the  bluish  pigment  in  solution. 

The  bile  pigment  is  absorbed  on  to  the  barium  sulphate  precipitate,  but  passes 
into  solution  again  in  acid  alcohol.  The  chlorate  acts  as  a  very  weak  oxidizing 
reagent,  converting  bilirubin  and  biliverdin  to  the  characteristic  blue  compound. 

The  author  claims  that  it  is  a  very  much  more  delicate  test  than  Gmelin's  Test. 

Tests  for  Bile  Acids 

1.  Sucrose — H2SO4  Test  (Pettenkofer). — To  5  c.c.  of  urine  in  a  test-tube  add 
5  drops  of  a  5  per  cent  solution  of  sucrose.    Now  incline  the  tube,  run  about 
2-3  c.c.  of  concentrated  sulphuric  acid  carefully  down  the  side  and  note  the 
red  ring  at  the  point  of  contact.    Upon  slightly  agitating  the  contents  of  the 
tube  the  whole  solution  gradually  assumes  a  reddish  color.    As  the  tube  be- 
comes warm,  it  should  be  cooled  in  running  water  in  order  that  the  tempera- 
ture may  not  rise  about  7o°C. 

It  is  claimed  that  this  test  is  not  satisfactory  in  the  presence  of 
protein  and  chromogenic  substances  which  yield  interfering  colors 
with  sulphuric  acid. 

2.  Furfural — H2SC>4  Test  (Mylius). — To  approximately  5  c.c.  of  urine  hi  a 
test-tube  add  3  drops  of  a  very  dilute  (i  :  1000)  aqueous  solution  of  furfural, 

HC— CH 

II      II 
HC     C.CHO. 


Now  incline  the  tube,  run  about  2-3  c.c.  of  concentrated  sulphuric  acid  carefully 
down  the  side  and  note  the  red  ring  as  above.  In  this  case  also,  upon  shaking 
the  tube,  the  whole  solution  is  colored  red.  Keep  the  temperature  below  7o°C. 
as  before. 

3.  Foam  Test  (v.  Udransky). — To  5  c.c.  of  urine  in  a  test-tube  add  3-4  drops 
of  a  very  dilute  (i  :  1000)  aqueous  solution  of  furfural.    Place  the  thumb  over  the 
top  of  the  tube  and  shake  until  a  thick  foam  is  formed.    By  means  of  a  small 
pipette  add  2-3  drops  of  concentrated  sulphuric  acid  to  the  foam  and  observe  the 
dark  pink  coloration  produced. 

4.  Surface  Tension  Test  (Hay). — This  test  is  based  upon  the  principle  that 
bile  acids  have  the  property  of  reducing  the  surface  tension  of  fluids  in  which 
they  are  contained.    The  test  is  performed  as  follows :  Cool  about  10  c.c.  of 
urine  in  a  test-tube  to  I7°C.  or  lower,  and  sprinkle  a  little  finely  pulverized  sul- 
phur upon  the  surface  of  the  fluid.    The  presence  of  bile  acids  is  indicated  if  the 
sulphur  sinks  to  the  bottom  of  the  liquid,  the  rapidity  with  which  the  sulphur  sinks 
depending  upon  the  amount  of  bile  acids  present  in  the  urine.    The  test  is  said  to 
react  with  bile  acids  when  the  latter  are  present  in  the  proportion  i  :  120,000. 
Allen1  has  recently  suggested  the  quantitative  determination  of  bile  acids  by  a 

1  Allen:  Jour.  Biol.  Chem.,  22,  505,  1915. 
29 


45° 


PHYSIOLOGICAL   CHEMISTRY 


surface  tension  method.    Urines  preserved  with  thymol  may  respond  positively 
to  this  test. 

CH3 

I 
ACETONE,    C  =  O. 

CH3 

It  was  formerly  very  generally  believed  that  acetone  appeared  in  the 
urine  under  pathological  conditions  because  of  increased  protein  de- 
composition. It  is  now  generally  thought  that,  in  man,  the  output 
of  acetone  arises  principally  from  the  breaking  down  of  fatty  tissues 
or  fatty  foods  within  the  organism.  The  quantity  of  acetone  elimi- 
nated has  been  shown  to  increase  when  the  subject  is  fed  an  abundance 
of  fat-containing  food  as  well  as  during  fasting,  whereas  a  replace- 
ment of  the  fat  with  carbohydrates  is  followed  by  a  marked  decrease 
in  the  acetone  excretion.  If  no  carbohydrate  food  is  fed  the  output  of 
acetone  bodies  increases  at  once,  producing  a  physiological  acidosis 
j^jQiafrt^^  . 

Acetone  and  the  closely  related  bodies,  /3-hydroxybutyric  acid  and 
acetoacetic  acid,  are  generally  classified  as  the  acetone  bodies.  They 
are  all  associated  with  a  deranged  metabolic  function  and  may  appear 
in  the  urine  together  or  separately,  depending  upon  the  conditions. 
Acetone  and  diacetic  acid  may  occur  alone  in  the  urine  but  /3-hy- 
droxybutyric  acid  is  never  found  except  in  conjunction  with  one  or  the 
other  of  these  bodies.  Both  acetone  and  /3-hydroxybutyric  acid  may 
be  formed  from  acetoacetic  acid.  The  relation  existing  between  these 
three  bodies  is  as  follows:1 

CH3CO.CH2.COOH->CH3CO.CH3+C02. 

Acetoacetic  acid.  Acetone. 

H  (reduction) 


CH3CHOH.CH2COOH. 

/3-hydroxybutyric  acid. 

Acetone,  chemically  considered,  is  a  ketone,  di-methyl  ketone.  When 
pure  it  is  a  liquid  which  possesses  a  characteristic  aromatic  fruit-like 
odor,  boils  at  56-57°C.  and  is  miscible  with  water,  alcohol,  or  ether 
in  all  proportions.  Acetone  is  a  physiological  as  well  as  a  pathological 
constituent  of  the  urine  and  under  normal  conditions  the  daily  output 
(preformed  acetone  +  acetoacetic  acid)  is  about  3-15  mg. 

1  Maase:  Med.  Klinik,  61,  445,  1910. 
Blum:  Munch,  med.  Woch.,  57,  683,  1910. 
Dakin:  Jour.  Biol.  Chem.,  8,  97,  1910. 
Marriott:  Jour.  Biol.  Chem.,  18,  241,  1914. 
Mathews:  Physiological  Chemistry,  26.  Ed.,  1916,  p.  756. 
Allen:  Am.  Jour.  Med.  Sci.,  153,  313,  1917. 


URINE  451 

Pathologically,  the  elimination  of  acetone  is  often  greatly  increased 
and  at  such  times  a  condition  of  acetonuria  is  said  to  exist.  Values 
from  0.02-6  grams  or  higher  have  been  obtained  for  preformed  acetone 
plus  acetone  derived  from  acetoacetic  acid.  This  pathological  ace- 
tonuria may  accompany  diabetes  mellitus,  scarlet  fever,  typhoid 
fever,  pneumonia,  nephritis,  phosphorus  poisoning,  grave  anemias, 
fasting,  and  a  deranged  digestive  function;  it  also  frequently  accom- 
panies auto-intoxication  and  chloroform  and  ether  anesthesia.  The 
types  of  acetonuria  most  frequently  met  with  are  those  noted  in  febrile 
conditions  and  in  advanced  cases  of  diabetes  mellitus.  The  blood  in 
diabetic  comas  has  been  found  to  contain  as  high  as  45  mg.  of  total 
acetone  (acetone  +  acetoacetic  acid)  for  100  c.c.  of  blood  serum. 

.    EXPERIMENTS 

1.  Isolation  from  the  Urine. — In  order  to  facilitate  the  detection  of  acetone  in 
the  urine,  the  specimen  under  examination  should  be  Distilled  and  the  tests  as  given 
below  applied  to  the  resulting  distillate.    If  it  is  not  convenient  to  distil  the  urine,, 
the  tests  may  be  conducted  upon  the  undistilled  fluid.    To  obtain  an  acetone  dis- 
tillate proceed  as  follows:    Place  100-250  c.c.  of  urine  in  a  distillation  flask  or  retort 
and  render  it  acid  with  acetic  acid.     Collect  about  one-third  of  the  original  volume 
of  fluid  as  a  distillate,  add  5  drops  of  10  per  cent  hydrochloric  acid  and  redistil  about 
one-half  of  this  volume.     With  this  final  distillate  conduct  the  tests  as  given  below. 

2.  Gunning's  lodoform  Test. — To  about  5  c.c.  of  the  urine  or  distillate  in 
a  test-tube  add  a  few  drops  of  LugoPs  solution1  or  ordinary  iodine  solution  (I  in 
KI)  and  a  few  drops  of  dilute  NH4OH  to  form  a  black  precipitate  (nitrogen  iodide). 
Allow   the  tube  to  stand  (the  length  of  time  depending  upon  the  content  of 
acetone  in  the  fluid  under  examination)  and  note  the  formation  of  a  yellowish  sedi- 
ment consisting  of  iodoform.     Examine  the  sediment  under  the  microscope  and 
compare  the  form  of  the  crystals  with  those  shown  in  Fig.  4,  page  30. 

If  the  crystals  are  not  well  formed  recrystallize  them  from  ether 
and  examine  again.  The  crystals  of  iodoform  should  not  be  confounded 
with  those  of  calcium  phosphate  (Fig.  no,  page  340)  which  maybe  formed 
in  this  test,  particularly  if  made  upon  the  undistilled  urine.  This  test 
is  preferable  to  Lieben's  test  (4)  since  no  substance  other  than  acetone 
will  produce  iodoform  when  treated  according  to  the  directions  for 
this  test;  both  alcohol  and  aldehyde  yield  iodoform  when  tested  by 
Lieben's  test. 

Gunning's  test  is  rather  satisfactory  for  the  detection  of  acetone, 
and  has  been  used  with  good  results  even  upon  the  undistilled  urine. 
Protein  material  apparently  interferes  with  the  reaction,  and  when 
present  the  urine  should  be  distilled  and  the  distillate  used.2  In 

1  Lugpl's  solution  may  be  prepared  by  dissolving  4  grams  of  iodine  and  6  grams  of  potas- 
sium iodide  in  100  c.c.  of  distilled  water. 

8  Rosenbloom:  Jour.  Am.  Med.  Ass'n,  59,  445,  1912. 


452  PHYSIOLOGICAL  CHEMISTRY 

some  instances  where  the  amount  of  acetone  present  is  very  small  it 
is  necessary  to  allow  the  tube  to  stand  24  hours  before  making  the  ex- 
amination for  iodoform  crystals.  This  test  serves  to  detect  acetone 
when  present  in  the  ratio  i :  100,000. 

3.  Sodium  Nitroprusside  Test  (Legal). — Introduce  about  5  c.c.  of  the  urine  or 
distillate  into  a  test-tube,  add  a  few  drops  of  freshly  prepared  aqueous  solution 
of  sodium  nitroprusside  and  render  the  mixture  alkaline  with  potassium  hydrox- 
ide.    (Be  sure  to  add  the  nitroprusside  before  the  solution  is  rendered  alkaline.) 
A  ruby-red  color,  which  may  be  due  to  creatinine,  a  normal  urinary  constituent, 
or  to  acetone,  or  to  acetone  and  creatinine  is  produced  (see  WeyPs  test,  page 
402).    Add  an  excess  of  acetic  acid  and  if  acetone  is  present  the  red  color  will 
be  intensified,  whereas  hi  the  absence  of  acetone  a  yellow  color  will  result. 
Make  a  control  test  upon  normal  urine  to  show  that  this  is  so. 

A  similar  red  color  may  be  produced  by  paracresol  in  urines  con- 
taining no  acetone. 

Two  hypotheses  have  been  proposed  to  explain  the  color  reaction 
between  acetone  and  nitroprusside:  (i)  The  formation  of  a  complex  ion 
of  ferropentacyanide  with  the  isonitroso  compound  of  the  ketone, 
or  (2)  the  formation  of  such  an  ion  with  the  isonitroamine  derivative 
of  the  ketone.1 

4.  Iodoform  Test  (Lieben). — Introduce  5  c.c.  of  the  urine  or  distillate  into  a 
test-tube,  render  it  alkaline  with  potassium  hydroxide  and  add  1-2  c.c.  of  iodine 
solution  drop  by  drop.    If  acetone  is  present  a  yellowish  precipitate  of  iodoform 
will  be  produced.    Identify  the  iodoform  by  means  of  its  characteristic  odor  and 
its  typical  crystalline  form  (see  Fig.  4,  page  30). 

While  fully  as  delicate  as  Gunning's  test  (2)  this  test  is  not  as 
accurate  since,  by  means  of  the  procedure  involved,  either  alcohol  or 
aldehyde  will  yield  a  precipitate  of  iodoform.  This  test  is  especially 
liable  to  lead  to  erroneous  deductions  when  urines  from  the  advanced 
stages  of  diabetes  are  under  examination,  because  of  the  presence  of 
alcohol  formed  from  the  sugar  through  fermentative  processes.2  If 
protein  is  present  in  the  urine  to  be  tested  it  may  prevent  the  acetone 
from  responding  to  the  above  reaction.  It  is  therefore  advisable  to  use 
the  distillate  to  secure  most  accurate  results.3  Sobel4  has  suggested  a 
quantitative  method  for  acetone  based  on  Lieben's  test. 

5.  Salicylaldehyde  Reaction  (Frommer). — Render  10  c.c.  of  urine  strongly 
alkaline  with  potassium  hydroxide,  add  10-12  drops  of  a  10  per  cent  solution  of 

1  Cambi:  *Atti.  accad.  Lincei,  22,  376,  1913. 

2  Welker  reports  the  production  of  a  pink  or  red  color  during  the  application  of  this  test 
to  the  distillates  from  pathological  urines  which  had  been  preserved  with  powdered  thymol. 
He  found  the  color  to  be  due  to  an  iodothymol  compound  which  had  been  previously  pre- 
pared synthetically  by  Messinger  and  Vortmann. 

3  Rosenbloom:  Jour.  Am.  Med.  Ass'n,  59,  445,  1912. 

4  Sobel:  Schweiz.  Apoth.  Ztg.,  52,  62,  1914. 


URINE  453 

salicylaldehyde  in  absolute  alcohol  and  warm  the  mixture  to  about  70°.  If 
acetone  be  present  the  fluid  becomes  yellow,  then  red,  reddish-purple  and  dark 
red  in  turn.  The  color  of  the  urine  is  practically  unchanged  if  no  acetone  is 
present. 

This  color  is  due  to  the  formation  of  dihydroxydibenzoylacetone 
through  the  interaction  of  salicylaldehyde  and  acetone. 

CH3 

I 

ACETO ACETIC  ACID,  C  =  O 

CH2COOH. 

Acetoacetic  or  diacetic  acid  occurs  in  traces  in  normal  urine. 
The  sum  of  the  acetone  and  the  acetoacetic  acid  excreted  in  normal 
urine  per  day  ranges  from  3  to  15  mg.  and  ordinarily  three-quarters 
of  this  is  acetoacetic  acid.  Under  certain  pathological  conditions 
it  occurs  in  larger  quantities  and  is  rarely  found  except  associated 
with  acetone.  In  the  human  body  it  yields  /3-hydroxybutyric  acid 
by  reduction  and  upon  decomposition  yields  acetone  and  car- 
bon dioxide.  Acetoaceturia  occurs  ordinarily  under  the  same  condi- 
tions as  the  pathological  acetonuria,  i.e.,  in  fevers,  diabetes,  etc.  (pp. 
-45a-and  557).  If  very  little  acetoacetic  acid  is  formed  it  may  be 
transformed  into  acetone,  whereas  if  a  larger  quantity  is  produced  both 
acetone  and  acetoacetic  acid  may  be  present  in  the  urine.  Aceto- 
aceturia is  most  frequently  observed  in  children,  especially  accompany- 
ing fevers  and  digestive  disorders ;  it  is  perhaps  less  frequently  observed 
in  adults,  but  when  present,  particularly  in  fevers  and  diabetes  it  is 
frequently  followed  by  fatal  coma. 

Acetoacetic  acid  is  a  colorless  liquid  which  is  miscible  with  water, 
alcohol  and  ether,  in  all  proportions.  It  differs  from  acetone  in  giving 
a  violet-red  or  Bordeaux-red  color  with  a  dilute  solution  of  ferric 
chloride. 

EXPERIMENTS1 

i.  Le  Nobel  Reaction.2 — Make  10  c.c.  of  urine  acid  with  acetic  acid,  add  a 
few  drops  of  a  dilute  aqueous  solution  of  sodium  nitroprusside  and  stratify  con- 
centrated ammonium  hydroxide  upon  the  mixture.  In  the  presence  of  aceto- 
acetic acid  a  violet  ring  forms  at  once. 

Acetone  also  responds  to  this  test,  but  the  test  is  more  delicate  for  aceto- 
acetic acid  and  the  response  is  more  prompt. 

1  To  prepare  a  diacetic  acid  solution  which  may  be  added  to  urine,  if  urines  containing 
this  acid  are  not  available,  proceed  as  follows:    Treat  13  grams  of  ethyl  acetoacetate  with 
500  c.c.  of  N/5  sodium  hydroxide.    Allow  to  stand  for  48  hours  to  hydrolyze  the  ester. 
In  preparing  urine  for  tests  add  i  part  of  this  solution  to  10  parts  of  urine. 

2  Harding  and  Ruttan:  Biochem.  Jour.,  6,  445,  1912;  also  Biochem.  Bull.,  2,  223,  1913. 


454  PHYSIOLOGICAL  CHEMISTRY 

2.  Ferric  Chloride  Test  (Gerhardt). — To  5  c.c.  of  urine  in  a  test-tube  add 
ferric  chloride  solution,  drop  by  drop,  until  no  more  precipitate  forms.    In  the 
presence  of  acetoacetic  acid  a  Bordeaux-red  color  is  produced ;  this  color  may  be 
somewhat  masked  by  the  precipitate  of  ferric  phosphate,  in  which  case  the  fluid 
should  be  filtered. 

A  positive  result  from  the  above  manipulation  simply  indicates  the  possible 
presence  of  acetoacetic  acid.  Before  making  a  final  decision  regarding  the  pres- 
ence of  this  body  make  the  two  following  control  experiments : 

(a)  Place  5  c.c.  of  urine  in  a  test-tube,  small  beaker,  or  Erlenmeyer  flask 
and  boil  it  vigorously  for  3-5  minutes.    Cool  the  vessel  and,  with  the  boiled 
urine,  make  the  test  as  given  above.    As  has  been  already  stated,  acetoacetic 
acid  yields  acetone  upon  decomposition  and  acetone  does  not  give  a  Bordeaux- 
red  color  with  ferric  chloride.    By  boiling  as  indicated  above,  therefore,  any 
acetoacetic  acid  present  would  be  decomposed  into  acetone  and  carbon  dioxide 
and  the  test  upon  the  resulting  fluid  would  be  negative.    If  positive,  the  color 
is  due  to  the  presence  of  bodies  other  than  acetoacetic  acid. 

(b)  Place  5  c.c.  of  urine  in  a  test-tube,  acidify  with  H2SO4,  to  free  aceto- 
acetic acid  from  its  salts,  and  carefully  extract  the  mixture  with  ether  by  shaking. 
If  acetoacetic  acid  is  present  it  will  be  extracted  by  the  ether.    Now  remove 
the  ethereal  solution,  evaporate  it  to  dryness,  dissolve  the  residue  hi  1-2  c.c. 
of  water  and  add  3-5  drops  of  3  per  cent  ferric  chloride.    Acetoacetic  acid  is 
indicated  by  the  production  of  the  characteristic  Bordeaux-red  color. 

This  color  disappears  spontaneously  in  24-48  hours.  Such  sub- 
stances as  antipyrin,  kairin,  phenacetin,  salicylic  acid,  salicylates, 
sodium  acetate,  thiocyanates,  and  thallin  yield  a  similar  red  color 
under  these  conditions,  but  when  due  to  the  presence  of  any  of  these 
substances  the  color  does  not  disappear  spontaneously  but  may  re- 
main permanent  for  days.  Many  of  these  disturbing  substances  are 
soluble  in  benzene  or  chloroform  and  may  be  removed  from  the  urine 
by  this  means  before  extracting  with  ether  as  above.  Acetoacetic 
acid  is  insoluble  in  benzene  or  chloroform. 

Maxwell1  points  out  possible  error  in  use  of  ferric  chloride  test  for 
acetoacetic  acid  in  urine  of  patients  taking  sodium  bicarbonate. 

3.  Sodium  Nitrite— Ferrous   Sulphate   Reaction  (Hurtley).— Place  10  c.c. 
of  urine  in  a  large  test-tube,  add  2.5  c.c.  of  concentrated  hydrochloric  acid 
and  i  c.c.  of  fresh  i  per  cent  sodium  nitrite.    Shake  the  tube  and  permit  it  to 
stand  for  two  minutes.    Add  15  c.c.  of  concentrated  ammonium  hydroxide  and 
5  c.c.  of  10  per  cent  ferrous  sulphate.    Shake  the  tube  and  permit  it  to  stand. 
Note  the  slow  development  of  a  violet  or  purple  color  hi  the  presence  of  aceto- 
acetic acid. 

This  test  serves  to  detect  acetoacetic  acid  when  present  in  a  dilu- 
tion of  i  to  50,000.  The  concentration  of  the  acetoacetic  acid  regulates 
the  speed  at  which  the  color  develops.  If  the  concentration  be  very 

1  Maxwell:  Med.  Jour.  Australia,  i,  458,  1920. 


URINE  455 

low  an  interval  of  five  hours  may  elapse  before  the  color  appears. 
The  test  is  believed  to  be  specific  for  acetoacetic  acid. 

H    OHH 

I       I       I 

0-HYDROXYBUTYRIC  ACID,   H — C — C — C — COOH. 

I        I         I 

H    H    H 

This  acid  occurs  in  normal  urine  in  traces,  e.g.,  20—30  mg.  per  day.1 
It  is  found  under  certain  pathological  conditions  in  larger  quantities 
and  then  always  in  conjunction  with  either  acetone  or  acetoacetic 
acid.  It  is  present  in  especially  large  amount  in  severe  cases 
of  diabetes  and  has  also  been  detected  in  digestive  disturbances, 
continued  fevers,  scurvy,  measles,  and  in  fasting.  It  is  probable 
that,  in  man,  jS-hydroxybutyric  acid,  in  common  with  acetone  and 
acetoacetic  acid,  arises  principally  from  the  breaking  down  of  fatty 
tissues  within  the  organism.  Any  condition  in  which  large  amounts 
of  acetone  and  acetoacetic  acid,  and  in  severe  cases  ]8-hydroxybutyric 
acid  also,  are  excreted  in  the  urine  is  known  as  an  "acidosis."  In 
diabetes  the  deranged  metabolic  conditions  cause  the  production  of 
great  quantities  of  these  substances  which  lead  to  an  acid  intoxication 
and  ultimately  to  diabetic  coma.  In  severe  diabetes  50—100  grams 
or  over  per  day  may  be  excreted.  In  such  conditions  the  /3-hy- 
droxybutyric  acid  may  constitute  60-80  per  cent  of  the  total  acetone 
bodies.  In  rare  cases  we  may  have  an  excretion  of  large  amounts  of 
0-hydroxybutyric  acid  with  a  low  acetone  output.  An  acidosis  may 
also  occur  under  certain  physiological  conditions  (see  Chapter  XVII  on 
Acidosis  and  Chapter  XXVIII  on  Metabolism). 

Ordinarily  0-hydroxybutyric  acid  is  an  odorless,  transparent  syrup 
which  is  levorotatory  and  easily  soluble  in  water,  alcohol,  and  ether; 
it  may  be  obtained  in  crystalline  form. 

EXPERIMENTS 

i.  Black's  Reaction.2 — Inasmuch  as  the  urinary  pigments  as  well  as  any 
contained  sugar  or  acetoacetic  acid  will  interfere  with  the  delicacy  of  this  test 
when  applied  to  the  urine  directly,  the  following  preliminary  procedure  is  neces- 
sary: Concentrate  10  c.c.  of  the  urine  under  examination  to  one-third  or  one- 
fourth  of  its  original  volume  hi  an  evaporating  dish  at  a  gentle  heat.  Acidify 
the  residue  with  a  few  drops  of  concentrated  hydrochloric  acid,  add  sufficient 
plaster  of  Paris  to  make  a  thick  paste  and  allow  the  mixture  to  stand  until  it 
begins  to  "set."  It  should  now  be  stirred  and  broken  up  hi  the  dish  by  means 
of  a  stirring  rod  with  a  blunt  end.  Extract  the  porous  meal  thus  produced  twice 

1  Shaffer  and  Marriott:  Jour.  Biol.  Chem.,  i<5,  265,  1913. 

2  Black:  Jour.  Biol.  Chem..  5,  207,  1908. 


456  PHYSIOLOGICAL   CHEMISTRY 

with  ether  by  stirring  and  decantation.  Any  /?-hydroxybutyric  acid  present 
will  be  extracted  by  the  ether.  Evaporate  the  ether  extract  spontaneously  or 
on  a  water-bath,  dissolve  the  residue  in  water,  and  neutralize  it  with  barium 
carbonate.  To  5  to  10  c.c.  of  this  neutral  fluid  hi  a  test-tube  add  2  to  3  drops 
of  ordinary  commercial  acid  hydrogen  peroxide.  Mix  by  shaking  and  add  a 
few  drops  of  Black's  reagent.1  Permit  the  tube  to  stand  and  note  the  gradual 
development  of  a  rose  color  which  increases  to  its  maximum  intensity  and  then 
gradually  fades.2 

In  carrying  out  the  test  care  should  be  taken  to  see  that  the  solution 
is  cold  and  approximately  neutral  and  that  a  large  excess  of  hydrogen 
peroxide  and  Black's  reagent  are  not  added.  In  case  but  little 
/3-hydroxybutyrlc  acid  is  present  the  color  will  fail  to  appear  or  will 
be  but  transitory  if  the  oxidizing  agents  are  added  in  too  great  excess. 
It  is  preferable  to  add  a  few  drops  of  the  reagent  and  at  intervals  of 
a  few  minutes  repeat  the  process  until  the  color  undergoes  no  further 
increase  in  intensity.  One  part  of  /3-hydroxybutyric  acid  in  10,000 
parts  of  the  solution  may  be  detected  by  this  test. 

2.  Polariscopic  Examination. — Subject  some  of  the  urine  (free  from  protein) 
to  the  ordinary  fermentation  test  (see  page  437).  This  will  remove  glucose 
and  fructose,  which  would  interfere  with  the  polariscopic  test.  Now  examine  the 
fermented  fluid  in  the  polariscope  and  if  it  is  levorotatory  the  presence  of  /?-hy- 
droxybutyric  acid  is  indicated.  This  test  is  not  absolutely  reliable,  however,  since 
conjugate  glycuronates  are  also  levorotatory  after  fermentation. 

CONJUGATE  GLYCURONATES 

Glycuronic  acid  does  not  occur  free  in  the  urine,  but  is  found,  for 
the  most  part,  in  combination  with  phenol.  Much  smaller  quantities 
are  excreted  in  combination  with  indoxyl  and  skatoxyl.  The  total 
content  of  conjugate  glycuronates  seldom  exceeds  0.004  Per  cent  under 
normal  conditions.  The  output  may  be  very  greatly  increased  as 
the  result  of  the  administration  of  antipyrin,  borneol,  camphor, 
chloral  hydrate,  menthol,  morphine,  naphthol,  turpentine,  etc.  The 
glycuronates  as  a  group  are  levorotatory  whereas  glycuronic  acid  is 
dextrorotatory.  Most  of  the  glycuronates  reduce  alkaline  metallic 
oxides  and  so  introduce  an  error  in  the  examination  of  urine  for  sugar. 
Conjugate  glycuronates  often  occur  associated  with  glucose  in  glyco- 
suria,  diabetes  mellitus,  and  in  some  other  disorders.  As  a  class  the 
glycuronates  are  non-fermentable. 

EXPERIMENTS 

i.  Naphthoresorcinol  Reaction  (Tollens). — Introduce  5  c.c.  of  urine  in  a 
test-tube  and  add  0.5-1  c.c.  of  a  i  per  cent  solution  of  naphthoresorcinol  in 

1  Made  by  dissolving  5  grams  of  ferric  chloride  and  0.4  gram  of  ferrous  chloride  in  100 
c.c.  of  water. 

1  This  disappearance  of  color  is  due  to  the  further  oxidation  of  the  acetoacetic  acid. 


URINE 


457 


95  per  cent  alcohol,  and  5  c.c.  of  concentrated  hydrochloric  acid.  Raise  the 
temperature  gradually  to  the  boiling-point  and  boil  for  one  minute,  shaking  the 
tube  continuously.  Stand  the  tube  aside  four  minutes,  then  cool  under  the 
tap.  Extract  with  an  equal  volume  of  ether.  Glycuronates  are  indicated  by 
the  ether  extract  assuming  a  violet-red  color.  The  spectroscope  shows  this 
extract  to  possess  two  absorption  bands,  one  on  the  D  line  and  one  to  the  right 
of  this  line. 

2.  Polariscopic-Fermentation  Test. — If  glucose  is  present  in  the  urine  tested 
for  glycuronates  the  urine  may  first  be  subjected  to  a  polariscopic  examination, 
then  fermented  and  a  second  polariscopic  examination  made.  The  sugar  being 
dextrorotatory  and  fermentable  and  the  glycuronates  being  levorotatory  and 
non-fermentable  the  second  polariscopic  test  will  show  a  levorotation  indicative 
of  conjugate  glycuronates. 

3.  Reduction-Polariscopic  Test. — Test  the  urine  by  Fehling's  test.  If 
positive  try  the  Resorcinol-HCl  reaction  for  fructose.  If  negative  test  the  optical 
activity.  Levorotation  indicates  glycuronates. 

PENTOSES 

We  have  two  distinct  types  of  pentosuria,  i.e.,  alimentary  pentosuria, 
resulting  from  the  ingestion  of  large  quantities  of  pentose-rich  fruits 


FIG.  136. — PENTOSAZONE  CRYSTALS. 

Isolated  and  purified  in  the  author's  laboratory  by  Mr.  B.  L.  Fleming.  From  the  urine 
of  a  patient  in  the  service  of  Dr.  S.  Solis  Cohen,  Jefferson  Hospital,  Phila.  For  color  of 
crystals  see  Plate  III,  opposite  page  22. 

such  as  prunes,  cherries,  grapes,  or  plums,  and  fruit  juices,  in  which 
condition  the  pentoses  appear  only  temporarily  in  the  urine;  and  the 
chronic  form  of  pentosuria,  in  which  the  output  of  pentoses  bears  no 


458  PHYSIOLOGICAL   CHEMISTRY 

relation  whatever  to  the  quantity  and  nature  of  the  pentose  content 
of  the  food  eaten.  In  occurring  in  these  two  forms,  pentosuria  re- 
sembles glycosuria  (see  page  431),  but  it  is  definitely  known  that  pen- 
tosuria bears  no  relation  to  diabetes  mellitus  and  there  is  no  generally 
accepted  theory  to  account  for  the  occurrence  of  the  chronic  form  of 
pentosuria.  The  pentose  detected  most  frequently  in  the  urine  is 
arabinose,  the  inactive  form  generally  occurring  in  chronic  pentosuria 
although  active  forms  have  been  more  or  less  frequently  reported. 
Levene  and  La  Forge1  as  well  as  Zerner  and  Waltuch2  report  d-xylose, 
and  Hiller3  found  J-xyloketose  in  one  case  of  pentosuria.  The  levo- 
rotatory  variety  occurs  in  the  alimentary  type  of  the  disorder.  For 
pentosazone  crystals  (see  Fig.  136). 

EXPERIMENTS 

1.  Orcinol-Hydrochloric  Acid  Reaction  (Bial).4 — To  5  c.c.  of  Bial's  reagent1 
in  a  test-tube  add  2-3  c.c.  of  urine  and  heat  the  mixture  gently  until  the  first 
bubbles  rise  to  the  surface.6    Immediately  or  upon  cooling  the  solution  becomes 
green  and  a  flocculent  precipitate  of  the  same  color  may  form. 

This  test  is  believed  to  be  more  accurate  than  the  original  orcinol 
test.  It  is  claimed  that  urines  containing  menthol,  kreosotal,  etc., 
respond  to  the  old  orcinol  reaction,  but  not  to  Bial's.  If  so  desired 
the  osazone  of  the  pentose  (see  Fig.  136)  may  be  formed,  then  distilled 
with  hydrochloric  acid  and  the  distillate  tested  by  Bial's  test  (Jolles). 

2.  Phloroglucinol-Hydrochloric  Acid  Reaction  (Tollens). — To  equal  volumes 
of  urine  and  hydrochloric  acid  (sp.  gr.  1.09)  add  a  little  phloroglucinol  and  heat 
the  mixture  on  a  boiling  water-bath.    Pentose,  galactose,  or  glycuronic  acid 
will  be  indicated  by  the  appearance  of  a  red  color.    To  differentiate  between 
these  bodies  examine  by  the  spectroscope  and  look  for  the  absorption  band 
between  D  and  E  given  by  pentoses  and  glycuronic  acid,  and  then  differentiate 
between  the  two  latter  bodies  by  the  melting-points  of  their  osazones. 

3.  Orcinol  Test — Place  equal  volumes  of  urine  and  hydrochloric  acid  (sp.  gr. 
1.09)  in  a  test-tube,  add  a  small  amount  of  orcinol,  and  heat  the  mixture  to  boiling. 
Color  changes  from  red  through  reddish-blue  to  green  will  be  noted.     When  the 
solution  becomes  green  it  should  be  shaken  in  a  separately  funnel  with  a  little 
amyl  alcohol,  and  the  alcoholic  extract  examined -spectroscopically.     An  absorption 
band  between  C  and  D  will  be  observed. 

1  Levene  and  La  Forge:  Jour.  Biol.  Chem.,  18,  319,  1914. 

J  Zerner  and  Waltuch:  Monatsh.  Chem.,  34,  1639,  1913;  35,  1025,  1914. 

1  Hiller:  Jour.  Biol.  Chem.,  30,  135,  1917. 

4  Bial:  Deut.  med.  Woch.,  28,  252,  1902. 

6  Orcinol 1.5  grams. 

Fuming  HC1 506  grams. 

Ferric  chloride  (10  per  cent) 20-30  drops. 

6  The  test  may  also  be  performed  by  adding  the  urine  to  the  hot  reagent.    No  further 
heating  should  be  necessary  if  pentose  is  present. 


URINE  459 

FAT 

When  fat  finds  its  way  into  the  urine  through  a  lesion  which  brings 
some  portion  of  the  urinary  passages  into  communication  with  the 
lymphatic  system  a  condition  known  as  chyluria  is  established.  The 
turbid  or  milky  appearance  of  such  urine  is  due  to  its  content  of  chyle. 
This  disease  is  encountered  most  frequently  in  tropical  countries,  but 
is  not  entirely  unknown  in  more  temperate  climates.  Albumin  is  a 
constant  constituent  of  the  urine  in  chyluria.  Upon  shaking  a  chylous 
urine  with  ether  the  fat  is  dissolved  by  the  ether  and  the  urine  becomes 
less  turbid  or  entirely  clear. 

HEMATOPORPHYRIN 

Urine  containing  this  body  is  occasionally  met  with  in  various 
diseases,  but  more  frequently  after  the  use  of  quinine,  tetronal,  trional, 
and  especially  sulphonal.  Such  urines  ordinarily  possess  a  reddish 
tint,  the  depth  of  color  varying  greatly  under  different  conditions. 

EXPERIMENTS 

1.  Spectroscopic  Examination. — To  100  c.c.  of  urine  add  about  20  c.c.  of 
a  10  per  cent  solution  of  potassium  hydroxide  or  ammonium  hydroxide.    The 
precipitate  which  forms  consists  principally  of  earthy  phosphates  to  which  the 
hematoporphyrin  adheres  and  is  carried  down.    Filter  off  the  precipitate,  wash 
it  and  transfer  to  a  flask  and  warm  with  alcohol- acidified  with  hydrochloric  acid. 
By  this  process  the  hematoporphyrin  is  dissolved  and  on  filtering  will  be  found 
hi  the  filtrate  and  may  be  identified  by  means  of  the  spectroscope  (see  page  300, 
and  Absorption  Spectra,  Plate  II). 

2.  Acetic  Acid  Test. — To  100  c.c.  of  urine  add  5  c.c.  of  glacial  acetic  acid  and 
allow  the  mixture  to  stand  48  hours.    Hematoporphyrin  deposits  in  the  form  of  a 
precipitate. 

LACTOSE 

Lactose  is  rarely  found  in  the  urine  except  as  it  is  excreted  by  women 
during  pregnancy,  during  the  nursing  period,  or  soon  after  weaning. 
It  is  rather  difficult  to  show  the  presence  of  lactose  in  the  urine  in  a 
satisfactory  manner,  since  the  formation  of  the  characteristic  lactos- 
azone  is  not  attended  with  any  great  measure  of  success  under  these 
conditions.  It  is,  however,  comparatively  easy  to  show  that  it  is  not 
glucose,  for,  while  it  responds  to  reduction  tests,  it  does  not  ferment 
with  pure  yeast  and  does  not  give  a  glucosazone.  An  absolutely 
conclusive  test,  of  course,  is  the  isolation  of  the  lactose  in  crystalline 
form  (Fig.  109,  page  335)  from  the  urine. 

On  oxidation  with  nitric  acid  lactose  and  galactose  yield  mucic  acid. 
This  test  is  frequently  used  in  urine  examination  to  differentiate  lactose 
and  galactose  from  other  reducing  sugars.  To  differentiate  lactose 


460  PHYSIOLOGICAL  CHEMISTRY 

from  pentose,  since  neither  ferments,  we  may  apply  the  Orcinol — HC1 
test  of  Bial,  see  page  458.  To  show  lactose  in  the  presence  of  glucose 
the  latter  may  first  be  removed  by  fermentation.1 

EXPERIMENTS 

1.  Mucic  Acid  Test. — Treat  100  c.c.  of  the  urine  under  examination  with 
20  c.c.2  of  concentrated  nitric  acid  and  evaporate  the  mixture  in  a  broad,  shallow 
glass  vessel,  upon  a  boiling  water -bath  until  the  volume  of  the  solution  is  only 
about  20  c.c.    At  this  point  the  fluid  should  be  clear  and  a  fine  white  precipitate 
of  mucic  acid  should  separate. 

If  the  percentage  of  lactose  in  the  urine  is  low  it  may  be  necessary 
to  cool  the  solution  and  permit  it  to  stand  for  some  time  before  the 
precipitate  will  form.  It  is  impossible  to  differentiate  between  galactose 
and  lactose  by  means  of  this  test,  but  the  reaction  does  serve  to  dif- 
ferentiate these  two  sugars  from  all  other  reducing  sugars.  A  sat- 
isfactory differentiation  between  lactose  and  galactose  in  pure  solution 
may  be  made  by  means  of  Barfoed's  test,  page  29.  This  test  is, 
however,  not  suited  for  urine  examination.  To  differentiate  galactose 
and  lactose  in  urine  use  the  Phloroglucinol-Hydrochloric  Acid  Reaction 
of  Tollens,  see  pages  36  and  461. 

2.  Compound  Test. — Try  the  Nylander  reaction.     If  positive  try  the  phenyl- 
hydrazine  test.    If  negative  (the  lactosazone  is  not  readily  formed  in  urine)  ap- 
ply the  fermentation  test.     If  this  test  is  also  negative,  differentiate  between 
lactose  and  pentose  by  Orcinol-HCl  reaction  (Bial)  and  mucic  acid  tests. 

GALACTOSE 

Galactose  has  occasionally  been  detected  in  the  urine,  and  in  par- 
ticular in  that  of  nursing  infants  afflicted  with  a  deranged  digestive 
function.  Lactose  and  galactose  may  be  differentiated  from  other 
reducing  sugars  which  may  be  present  in  the  urine  by  means  of  the 
mucic  acid  test.  This  test  simply  consists  in  the  production  of  mucic 
acid  through  oxidation  of  the  sugar  with  nitric  acid. 

EXPERIMENTS 

i.  Mucic  Acid  Test— Treat  100  c.c.  of  the  urine  under  examination  with 
20  c.c.3  of  concentrated  nitric  acid  and  evaporate  the  mixture  hi  a  broad,  shallow 
glass  vessel,  upon  a  boiling  water-bath,  until  the  volume  of  the  solution  is  only 
20  c.c.  At  this  point  the  fluid  should  be  clear  and  a  fine,  white  precipitate  of 
mucic  acid  should  separate. 

1Mathews:  Sour.  Am.  Med.  Ass'n,  75,  1568,  1920. 

2  If  the  specific  gravity  of  the  urine  is  102001  over,  it  is  necessary  to  use  25-35  c.c.  of 
nitric  acid.  Under  these  conditions  the  mixture  should  be  evaporated  until  the  remaining 
volume  is  approximately  equivalent  to  that  of  the  nitric  acid  added. 

*  If  the  specific  gravity  of  the  urine  is  1020  or  over  it  is  necessary  to  use  25-35  c.c.  of 
nitric  acid.  Under  these  conditions  the  mixture  should  be  evaporated  until  the  remaining 
volume  is  approximately  equivalent  to  that  of  the  nitric  acid  added. 


URINE  461 

If  the  percentage  of  galactose  present  in  the  urine  is  low  it  may  be 
necessary  to  cool  the  solution  and  permit  it  to  stand  for  some  time 
before  the  precipitate  will  form.  It  is  impossible  to  differentiate 
between  galactose  and  lactose  by  means  of  this  test,  but  the  reaction 
does  serve  to  differentiate  these  two  sugars  from  all  other  reducing 
sugars.  A  satisfactory  differentiation  between  galactose  and  lactose 
may  be  made  by  the  Phloroglucinol-Hydrochloric  Acid  Test  of  Tollens, 
below. 

2.  Phloroglucinol-Hydrochloric  Acid  Reaction  (Tollens). — To  equal  volumes  of 
the  urine  and  hydrochloric  acid  (sp.  gr.  1.09)  add  a  little  phloroglucinol  and  heat 
the  mixture  on  a  boiling  water-bath.  Galactose,  pentose,  and  glycuronic  acid  will 
be  indicated  by  the  appearance  of  a  red  color.  Galactose  may  be  differentiated 
from  the  two  latter  substances  in  that  its  solutions  exhibit  no  absorption  bands 
upon  spectroscopical  examination. 

FRUCTOSE 

Diabetic  urine  frequently  possesses  the  power  of  rotating  the  plane  of 
polarized  light  to  the  left,  thus  indicating  the  presence  of  a  levorotatory 
substance.  The  levorotation  is  sometimes  due  to  the  presence  of 
fructose,  although  not  necessarily  confined  to  this  carbohydrate,  since 
conjugate  glycuronates  and  /3-hydroxybutyric  acid,  two  other  levo- 
rotatory bodies,  are  frequently  found  in  the  urine  of  diabetics.  Fructose 
is  invariably  accompanied  by  glucose  in  diabetic  urine,  but  fruc- 
tosuria  has  been  observed  as  a  separate  anomaly.  The  presence  of 
fructose  may  be  inferred  when  the  percentage  of  sugar,  as  determined 
by  the  titration  method,  is  greater  than  the  percentage  indicated  by 
the  polariscopic  examination. 

EXPERIMENTS 

i.  Borchardt' s  Reaction. — To  about  5  c.c.  of  urine  in  a  test-tube  add  ah  equal 
volume  of  25  per  cent  hydrochloric  acid  and  a  few  crystals  of  resorcinol.  Heat  to 
boiling  and  after  the  production  of  a  red  color,  cool  the  tube  under  running  water 
and  transfer  to  an  evaporating  dish  or  beaker.  Make  the  mixture  slightly  alka- 
line with  solid  potassium  hydroxide,  return  it  to  a  test-tube,  add  2-3  c.c.  of 
acetic  ether,  and  shake  the  tube  vigorously.  In  the  presence  of  fructose  the 
acetic  ether  is  colored  yellow. 

The  only  urinary  constituents  which  interfere  with  the  test  are 
nitrites  and  indican  and  these  interfere  only  when  they  are  simul- 
taneously present.  Under  these  conditions,  the  urine  should  be  acidified 
with  acetic  acid  and  heated  to  boiling  for  one  minute  to  remove  the 
nitrites.  In  case  the  indican  content  is  very  large,  it  will  impart  a  blue 
color  to  the  acetic  ether,  thus  masking  the  yellow  color  due  to  fructose. 
When  such  urines  are  to  be  examined,  the  indican  should  first  be  re- 


462  PHYSIOLOGICAL   CHEMISTRY 

moved  by  Obermayer's  test  (see  page  405).  The  chloroform  should 
then  be  discarded,  the  acid-urine  mixture  diluted  with  one-third  its 
volume  of  water,  and  the  test  applied  as  described  above.  The  urine 
of  patients  who  have  ingested  santonin  or  rhubarb  responds  to  the  test. 
The  test  will  serve  to  detect  fructose  when  present  in  a  dilution 
of  i :  2000,  i.e.,  0.05  per  cent. 

2.  Resorcinol-Hydrochloric  Acid  Reaction  (Seliwanoff). — To  5  c.c.  of  Seliwa- 
noff's  reagent1  in  a  test-tube  add  a  few  drops  of  the  urine  under  examination 
and  heat  the  mixture  to  boiling.    The  presence  of  fructose  is  indicated  by  the 
production  of  a  red  color  and  the  separation  of  a  red  precipitate.    The  latter 
may  be  dissolved  in  alcohol  to  which  it  will  impart  a  striking  red  color. 

If  the  boiling  be  prolonged  a  similar  reaction  may  be  obtained  with 
urines  containing  glucose.  This  has  been  explained2  in  the  case  of 
glucose  as  due  to  the  transformation  of  the  glucose  into  fructose  by 
the  catalytic  action  of  the  hydrochloric  acid.  The  precautions  neces- 
sary for  a  positive  test  for  fructose  are  as  follows :  The  concentration  of 
the  hydrochloric  acid  must  not  be  more  than  12  per  cent.  The  reac- 
tion (red  color)  and  the  precipitate  must  be  observed  after  not  more  than 
20-30  seconds  of  boiling.  Glucose  must  not  be  present  in  amounts 
exceeding  2  per  cent.  The  precipitate  must  be  soluble  in  alcohol  with 
a  bright  red  color. 

3.  Phenylhydrazine  Test. — Make  the  test  according  to  directions  under  Glu- 
cose, 3,  page  22. 

4.  Polariscopic  Examination. — A  simple  polariscopic  examination,  when  taken 
in  connection  with  other  ordinary  tests,  will  furnish  the  requisite  data  regarding 
the  presence  of  fructose,  provided  fructose  is  not  accompanied  by  other  levorotatory 
substances,  such  as  conjugate  glycuronates  and  /3-hydroxybutyric  acid. 

ARSENIC 

When  any  soluble  form  of  arsenic  is  introduced  into  the  body  in 
any  way,  it  is  quickly  absorbed  and  distributed  by  the  blood  and 
lymph.  The  absorption  is  influenced  by  the  quantity  and  quality  of 
the  food  in  the  stomach,  and  the  activity  of  the  circulation  of  the  part 
in  contact  with  the  poison.  Some  of  the  absorbed  arsenic  may  be 
returned  to  the  alimentary  canal  by  way  of  the  bile  and  gastro-intes- 
tinal  mucous  membrane.  After  absorption  it  may  be  deposited  in  the 
liver,  kidneys,  brain,  bone,  muscles,  and  walls  of  the  stomach  and 
intestines.  It  is  eliminated  in  all  of  the  excretions,  but  chiefly  by  the 
kidneys  and  through  the  feces.  It  does  not  appear  very  promptly  in 

1  Seliwanoff 's  reagent  may  be  prepared  by  dissolving  0.05  gram  of  resorcinol  in  100  c.c. 
of  dilute  (i  :  2)  hydrochloric  acid. 

*  Koenigsfeld:  Bioch.  Zeit.,  38,  311,  igi2. 


URINE 


463 


the  urine  but  continues  to  be  excreted  in  the  urine  over  a  long  period 
of  time,  in  some  cases  for  several  months.  The  urine  may  be  examined 
for  arsenic  by  the  following  methods. 

i.  Marsh  and  Marsh-Berzelius  Method. — This  method  has  the  advantage  of 
serving  as  a  qualitative  and  quantitative  determination,  and  is  a  very  delicate  test; 
it  is,  however,  long  and  tedious.  The  various  steps  in  the  analysis  are:  (i)  the 
destruction  of  the  organic  matter  in  the  urine;  (2)  treatment  with  sulphuric  acid  to 
drive  off  excess  nitric  acid  and  break  up  nitro-compounds;  and  (3)  application  of 
independent  test  to  the  resultant  solution.  Proceed  as  follows:  The  urine,  to 
which  is  added  one-third  its  volume  of  nitric  acid,  is  placed  in  a  casserole  or  evapo- 
rating dish  and  evaporated  at  65°-7o°C.  to  a  syrupy  consistency.  The  mass  is 
then  allowed  to  cool  and  5  c.c.  concentrated  sulphuric  acid  added,  and  gentle  heat 
applied.  The  heating  must  be  done  cautiously,  or  deflagration  takes  place  and 


FIG.  137. — MARSH  APPARATUS. 

some  of  the  arsenic  is  sure  to  be  lost.  The  mass  will  liquefy  and  finally  darken, 
indicating  organic  matter.  Cool  and  add  concentrated  nitric  acid,  i  c.c.,  and  apply 
very  gentle  heat;  copious  reddish-brown  fumes  are  evolved.  Gradually  raise  the 
temperature  until  darkening  of  the  solution  occurs,  then  cool,  add  i  c.c.  concentrated 
nitric  acid  and  again  apply  gentle  heat,  and  repeat  the  process  until  the  solution 
fails  to  darken.  Now  raise  the  temperature  until  white  fumes  begin  to  come  off. 
At  this  temperature  excess  nitric  acid  will  have  been  removed  and  all  nitro-com- 
pounds broken  up.  The  solution  at  this  point  is  clear  and  at  most  a  pale  straw  color. 
Cool  and  add  a  mixture  of  10  c.c.  concentrated  sulphuric  acid  and  40  c.c.  water, 
and  test  for  arsenic  using  a  Marsh  apparatus.  The  apparatus  (see  Fig.  137,  above) 
consists  of  a  wide- mouth  flask — 250  c.c.  capacity — fitted  with  a  two-hole  stopper. 
Through  one  hole  is  passed  the  stem  of  a  separatory  funnel  of  50  to  60  c.c.  capacity. 
Through  the  other  hole  a  piece  of  glass  tube  bent  at  right  angles,  which  is  fitted  to 
a  calcium  chloride  tube,  and  this  in  turn  to  a  narrow  quartz  tube,  the  distal  end  of 
which  is  drawn  to  a  fine  bore  and  bent  up>  almost  at  a  right  angle.  All  joints  must 
be  air-tight. 

Introduce  30  to  40  grams  of  arsenic-free  granulated  zinc  into  the  flask,  insert 
the  stopper  and  through  the  funnel  introduce  50  c.c.  dilute  sulphuric  acid  (i  part 


464  PHYSIOLOGICAL  CHEMISTRY 

to  4  parts  water).  After  a  few  minutes  collect  a  test-tube  of  gas  by  inverting  a 
test-tube  over  the  end  of  the  quartz  tube,  and  test  it  by  igniting.  When  the  gas  in 
the  test-tube  ignites  quietly,  light  the  gas  issuing  from  the  quartz  tube. 

Hold  a  clean  porcelain  crucible  lid  in  the  flame  and  note  whether  any  deposit 
occurs.  This  precaution  must  be  taken  to  insure  that  the  chemicals  and  apparatus 
are  not  contaminated  with  arsenic. 

Now  introduce  the  prepared  urine  solution  into  the  funnel  and  adjust  the  flow 
so  that  6  to  8  drops  are  introduced  into  the  flask  per  minute.  Immediately  hold  a 
clean  porcelain  crucible  lid  in  the  flame  and  at  the  first  evidence  of  a  dark  deposit 
apply  heat,  using  a  wing-top  burner,  to  the  quartz  tube.  The  arsenic  if  present 
will  deposit  in  the  quartz  tube  beyond  the  flame.  Now  test  the  spot  on  the  lid 
to  see  if  it  is  arsenic;  it  should  dissolve  readily  in  sodium  hypochlorite  solution. 
Continue  the  operation  for  two  hours,  remove  the  Bunsen  burner  and  again  hold 
the  lid  in  the  flame.  If  no  more  deposits  on  the  lid,  the  arsenic  has  all  come  over 
and  is  deposited  in  the  quartz  tube;  if  deposition  occurs,  apply  the  Bunsen  burner 
again  and  repeat. 

When  complete,  remove  the  quartz  tube,  weigh  it  after  cooling,  then  dissolve 
out  the  arsenic  with  nitric  acid,  wash,  dry,  and  weigh  again.  The  difference  in 
weight  is  the  weight  of  metallic  arsenic  in  the  volume  of  urine  taken. 

2.  Reinsch's  Test. — This  test  is  very  much  simpler,  but  not  so  delicate.  It 
has  the  advantage  of  application  in  the  presence  of  organic  matter.  The  test  is 
performed  as  follows:  The  urine,  acidified  with  one-fifth  its  volume  of  pure  hydro- 
chloric acid,  is  placed  in  a  beaker.  A  piece  of  bright  copper  foil  free  from  arsenic 
is  then  introduced,  and  the  urine  heated  almost  to  the  boiling-point.  It  is  then 
set  aside  for  six  to  eight  hours.  The  arsenic  is  deposited  on  the  copper  foil,  bluish- 
gray  color.  The  foil  is  then  removed,  washed  successively  in  pure  water,  alcohol, 
ether,  and  dried  without  heat.  The  foil  is  then  rolled  into  a  scroll  and  inserted 
into  a  3  mm.  bore  glass  tube  4  inches  long,  about  i  inch  from  the  end.  The  tube  is 
then  held  in  the  Bunsen  flame  at  an  angle  of  20  to  25  degrees  applying  heat  where 
the  copper  foil  is  situated.  The  arsenic  volatilizes  and  is  oxidized,  and  deposits  as 
octahedral  crystals  of  arsenic  trioxide  on  the  cooler  part  of  the  tube.  The  crystals 
can  readily  be  recognized  by  the  microscope  and  sometimes  with  a  simple  magnify- 
ing lens. 

MERCURY 

The  rapidity  of  absorption  of  mercury  depends  upon  a  number  of 
conditions  such  as,  mode  of  administration,  the  nature  of  the  com- 
pound and  its  physical  state,  the  state  and  condition  of  the  stomach 
and  intestines,  the  quantity  and  quality  of  the  food  in  the  stomach 
and  the  state  of  the  circulation  of  the  portal  of  entrance.  There  is 
no  definite  knowledge  as  to  the  form  in  which  it  is  absorbed.  Elimina- 
tion depends  upon  the  state  of  the  excretory  organs.  It  is  eliminated 
as  an  albuminate  in  all  the  excretions  of  the  body,  urine,  feces,  saliva, 
sweat,  tears,  and  milk.  Elimination  begins  about  two  hours  after 
introduction.  Depending  upon  the  amount  introduced  and  absorbed, 
the  time  required  for  its  complete  elimination  varies  from  24  hours  to 
many  weeks.  Mercury  may  be  detected  in  the  urine  by  the  following 
methods. 


URINE  465 

1.  Reinsch's  Test. — The  procedure  is  carried  out  in  the  same  manner  as  for 
arsenic  (see  above).     A  piece  of  arsenic-free  copper  foil  is  introduced  into  the  urine 
acidified  with  one-fifth  its  volume  of  pure  hydrochloric  acid.     The  urine  is,  how- 
ever, not  heated  to  boiling,  but  warmed  to  50°  or  60°  and  set  aside  for  12  hours 
or  preferably  24  hours.     Metallic  mercury  is  deposited  on  the  foil  as  a  bright  lus- 
trous mirror.     The  foil  is  then  washed  with  pure  water,  alcohol,  ether,  and  dried 
without  heat,  rolled  into  a  scroll,  inserted  into  a  glass  tube  and  heated  in  the  same 
manner  as  under  arsenic.     The  mercury  is  deposited  in  the  metallic  state  in  the 
form  of  globules  readily  distinguished  with  the  microscope. 

2.  Amalgamation  Test. — A  more  rapid  method  than  the  above  is  by  amalga- 
mation with  zinc.     Add  5  grams  of  zinc  dust  to  the  urine  and  heat  for  15  minutes, 
stirring  continuously.     Allow  the  amalgamated  zinc  to  settle  and  decant  the  urine. 
Then  wash  by  decantation  several  times  with  pure  water,  then  with  alcohol,  and 
finally  with  ether  and  dry  in  air.     Now  introduce  the  dry  zinc  into  a  narrow  dry 
glass  tube  sealed  at  one  end.     With  the  Bunsen  burner  soften  the  tube  about  2 
inches  above  the  zinc  and  constrict  the  tube  by  pulling  the  ends  apart.     Introduce  a 
small  bit  of  glass  wool  or  asbestos  sufficient  to  support  a  small  piece  of  iodine.    In- 
troduce the  iodine  supported  by  the  asbestos  at  the  constriction.     Apply  heat  to  the 
zinc  amalgam,  and  then  gently  to  the  region  holding  the  iodine  to  gently  volatilize 
it,  and  immediately  reapply  heat  to  the  zinc.     The  mercury  volatilizes  and  meeting 
the  iodine  vapor  unites  with  it,  and  is  deposited  as  the  red  iodide  of  mercury. 

CHOH 

/\ 

HOHC     CHOH 

INOSITOL, 

HOHC     CHOH 


'CHOH 

Inositol  occasionally  occurs  in  the  urine  in  albuminuria,  diabetes 
mellitus,  and  diabetes  insipidus.  It  is  claimed  also  that  copious  water- 
drinking  causes  this  substance  to  appear  in  the  urine.  Inositol  was  at 
one  time  considered  to  be  a  sugar  but  is  now  known  to  be  hexahy- 
droxybenzene,  as  the  above  formula  indicates.  It  is  an  example  of  a 
non-carbohydrate  in  whose  molecule  the  H  and  O  are  present  in  the 
proportion  to  form  water.  In  other  words  it  has  the  formula  of  the 
hexoses,  i.e.,  CeH^Oe.  Inositol  occurs  widely  distributed  in  the 
vegetable  kingdom,  and  because  of  this  fact  the  theory  has  been  voiced 
that  it  represents  one  of  the  first  stages  in  the  conversion  of  a  car- 
bohydrate into  the  benzene  ring.  It  is  found  in  the  liver,  spleen, 
lungs,  brain,  kidneys,  suprarenal  capsules,  muscles,  leucocytes,  testes, 
and  urine  under  normal  conditions. 

EXPERIMENT 

i.  Detection  of  Inositol  (Scherer).— Acidify  the  urine  with  concentrated  nitric 
acid  and  evaporate  nearly  to  dryness.    Add  a  few  drops  of  ammonium  hydroxide 
30 


466  PHYSIOLOGICAL  CHEMISTRY 

and  a  little  calcium  chloride  solution  to  the  moist  residue  and  evaporate  the  mixture 
to  dryness.    In  the  presence  of  inositol  (o.ooi  gram)  a  bright  red  color  is  obtained. 
For  a  more  satisfactory  test,  which  is  also  more  time-consuming,  see  Salkowski's1 
modification  of  Scherer's  test. 

LAIOSE 

This  substance  is  occasionally  found  in  the  urine  in  severe  cases  of 
diabetes  mellitus.  By  some  investigators  laiose  is  classed  with  the 
sugars.  It  resembles  fructose  in  that  it  has  the  property  of  reducing 
certain  metallic  oxides  and  is  levorotatory,  but  differs  from  fructose 
in  being  amorphous,  non-fermentable,  and  in  not  possessing  a  sweet 
taste. 

MELANINS 

These  pigments  never  occur  normally  in  the  urine,  but  are  present 
under  certain  pathological  conditions,  their  presence  being  especially 
associated  with  melanotic  tumors.  Ordinarily  the  freshly  passed  urine 
is  clear,  but  upon  exposure  to  the  air  the  color  deepens  and  may  at 
last  be  very  dark  brown  or  black  in  color.  The  pigment  is  probably 
present  in  the  form  of  a  chromogen  or  melanogen  and  upon  coming 
into  contact  with  the  air  oxidation  occurs,  causing  the  transforma- 
tion of  the  melanogen  into  melanin  and  consequently  the  darkening 
of  the  urine. 

It  is  claimed  that  melanuria  is  proof  of  the  formation  of  a  visceral 
melanotic  growth.  In  many  instances,  without  doubt,  urines  rich  in 
indican  have  been  wrongly  taken  as  diagnostic  proof  of  melanuria. 
The  pigment  melanin  is  sometimes  mistaken  for  indigo  and  melanogen 
for  indican.  It  is  comparatively  easy  to  differentiate  between  indigo 
and  melanin  through  the  solubility  of  the  former  in  chloroform. 

In  rare  cases  melanin  is  found  in  urinary  sediment  in  the  form  of  fine 
amorphous  granules. 

EXPERIMENTS 

1.  Ferric  Chloride  Reaction   (von  Jaksch-Pollak). — Add  a  few  drops  of 
ferric  chloride  solution  to  10  c.c.  of  urine  in  a  test-tube  and  note  the  formation  of 
a  gray  color.    Upon  the  further  addition  of  the  chloride  a  dark  precipitate  forms, 
consisting  of  phosphates  and  adhering  melanin.    An  excess  of  ferric  chloride 
causes  the  precipitate  to  dissolve. 

This  is  the  most  satisfactory  test  for  the  identification  of  melanin  in  the 
urine. 

2.  Bromine  Test  (Zeller). — To  50  c.c.  of  urine  in  a  small  beaker  add  an  equal 
volume  of  bromine  water.    In  the  presence  of  melanin  a  yellow  precipitate  will 
form  and  will  gradually  darken  in  color,  ultimately  becoming  black. 

1  Salkowski:  Zeit.  physiol.  chem.,  69,  478,  1910. 


URINE  467 

UROROSEIN 

This  is  a  pigment  which  is  not  present  in  normal  urine  but  may 
be  detected  in  the  urine  in  various  diseases,  such  as  pulmonary  tuber- 
culosis, typhoid  fever,  nephritis,  and  stomach  disorders.  Urorosein, 
in  common  with  various  other  pigments,  does  not  occur  preformed  in 
the  urine,  but  is  present  in  the  form  of  a  chromogen,  which  is  trans- 
formed into  the  pigment  upon  treatment  with  a  mineral  acid.  Herter1 
showed  this  chromogen  to  be  indole  acetic  acid, 

H 

C  •  C  •  COOH 
CH 

NH        H 

Normal  urine  responds  to  the  urorosein  reaction  (see  below)  if  nitrites 
are  present. 

EXPERIMENTS 

1.  Nitrite-Hydrochloric  Acid  Test  (Urorosein  Reaction). — To  10  c.c.  of  urine 
in  a  test-tube  add  2  c.c.  of  concentrated  hydrochloric  acid  and  a  few  drops  of  a 
i  per  cent  solution  of  potassium  nitrite.    A  rose-red  color  indicates  urorosein. 

The  chromogen  (indole  acetic  acid)  has  been  changed  into  urorosein 
by  oxidation. 

2.  Robin's  Reaction. — Acidify  10  c.c.  of  urine  with  about  15  drops  of  con- 
centrated hydrochloric  acid.     Upon  allowing  the  acidified  urine  to  stand,  a  rose-red 
color  will  appear  if  urorosein  is  present. 

3.  NencM  and  Sieber's  Reaction. — To  100  c.c.  of  urine  in  a  beaker  add  10  c.c. 
of  25  per  cent  sulphuric  acid.    Allow  the  acidified  urine  to  stand  and  note  the  ap- 
pearance of  a  rose-red  color.    The  pigment  may  be  separated  by  extraction  with 
amyl  alcohol. 

NEPHROROSEIN 

This  pigment  is  closely  related  to  urorosein2  and  like  urorosein  it  is 
produced  from  a  chromogen  when  the  urine  is  treated  with  nitric  acid 
or  with  concentrated  hydrochloric  acid  and  a  little  sodium  nitrite 
solution.  It  is  sometimes  called  ^-urorosein  to  differentiate  it  from  the 
true  urorosein  which  is  termed  a-urorosein.  Nephrorosein  occurs  only 
in  pathological  urines. 

DROCHROMOGEN 

This  is  the  chromogen  of  urochrome,  the  normal  urinary  pigment 
(see  Chapter  XXII) .  It  is  claimed  that  the  urochromogen  reaction  of  the 

1  Herter:  Jour.  Biol.  Chem.,  4,  253,  1908. 
3  Arnold:  Zeit.  physioL  Chem.,  71. 


468  PHYSIOLOGICAL  CHEMISTRY 

urine  is  an  aid  to  prognosis  and  diagnosis  of  pulmonary  tuberculosis. 
Urochromogen  is  not  present  in  normal  urine.  Its  presence  in  patho- 
logical urine  is  due  probably  to  faulty  oxidation,  i.e.,  failure  to  oxi- 
dize the  chromogen  to  urochrome.  Urochromogen  may  be  detected  by 
oxidizing  it  to  urochrome  by  means  of  potassium  permanganate.  In 
this  process  a  certain  antecedent  of  Urochromogen  is  also  oxidized 
to  urochrome.  Whereas  the  diazo  reaction  (see  page  469)  is  also 
given  by  urines  containing  Urochromogen,  it  is  claimed  that  the  diazo 
reaction  does  not  show  the  presence  of  the  precursor  of  Urochromogen. 
Hence  the  Urochromogen  reaction  is  said  to  be  more  constant  and 
uniform  in  its  appearance. 

EXPERIMENT 

Urochromogen  Reaction  (Weisz).1 — Fill  a  test-tube  a  little  less  than  one- 
third  full  of  urine,  dilute  it  with  2  volumes  of  distilled  water  and  mix  thoroughly. 
Pour  one-half  the  diluted  urine  into  another  tube  and  to  one  of  the  tubes  add  3 
drops  of  a  i  per  cent  solution  of  potassium  permanganate.  Shake  the  tube 
thoroughly.  In  the  presence  of  urochromogen  a  yellow  tint  will  appear  in  the 
tube  to  which  permanganate  was  added. 

The  reaction  is  due  to  the  oxidation  of  urochromogen  to  urochrome, 
and  is  believed  to  be  of  value  as  an  aid  in  prognosis  and  diagnosis  of 
pulmonary  tuberculosis.  The  presence  of  sugar,  albumin  or  urobilin 
in  low  concentration  does  not  interfere  with  the  test.  The  test  often 
runs  parallel  with  the  diazo  reaction  (see  below).  The  test  is  supposed 
to  be  positive  when  the  focus  of  the  lung  is  so  active  or  extensive  as  to 
flood  the  blood  with  toxins  or  to  break  down  the  defensive  forces  of  the 
body.  It  is  claimed,  therefore,  that  this  test  will  differentiate  the 
cases  in  which  the  tuberculosis  is  beyond  help  from  the  tuberculin 
from  those  in  which  the  body  is  liable  to  respond  favorably  to  its 
action.2  Some  investigators  claim  the  test  is  not  specific  and  that  a 
positive  reaction  will  be  obtained  in  many  disorders  other  than 
tuberculosis.3 

1  Weisz:  Munch,  med.  Woch.,  58,  1348,  1911. 

Vitri:  Semana  Medica,  20,  No.  28,  1913. 

Heflebower:  Am.  Jour.  Med.  Sci.,  143,  221,  1912. 

Metzger  and  Watson:  Jour.  Am.  Med.  Ass'n,  62,  1886,  1914. 

Pignacca:  Gazetta  d.  Osp.  e  delle  Clin.,  25,  353,  1914- 

Ferrannini:  Riforma  med.,  31,  479,  1915. 
8  M.  and  A.  Weisz:  Wien.  klin.  Woch.,  25,  1183,  1912. 

Dozzi:  Gazetta  d.  Osp.  e  delle  Clin.,  34,  815,  1914. 

Burgess:  Jour.  Am.  Med.  Ass'n,  66,  82,  1916. 
3  Tuliato:  Gazetta  d.  Osp.  e  delle  Clin.,  35,  1914. 

Martelli  and  Pizzetti:  Policlinico,  21,  April  i,  1914. 


URINE  469 


UNKNOWN  SUBSTANCES 

i.  Ehrlich's  Diazo  Reaction. — Place  equal  volumes  of  urine  and  Ehrlich's 
diazobenzenesulphonic  acid  reagent1  in  a  test-tube,  mix  thoroughly  by  shaking, 
and  quickly  add  ammonium  hydroxide  in  excess.  The  test  is  positive  if  both  the 
fluid  and  the  foam  assume  a  red  color.  If  the  tube  is  allowed  to  stand  a  precipi- 
tate forms,  the  upper  portion  of  which  exhibits  a  blue,  green,  greenish-black,ror 
violet  color.  Normal  urine  gives  a  brownish-yellow  reaction  with  the  above 
manipulation. 

The  exact  nature  of  the  substance  or  substances  upon  whose  presence 
in  the  urine  this  reaction  depends  is  not  well  understood.  Some  in- 
vestigators claim  that  a  positive  reaction  indicates  an  abnormal  de- 
composition of  protein  material,  whereas  others  assume  it  to  be  due 
to  an  increased  excretion  of  alloxyproteic  acid,  o^xyproteic  acid,  or  uro- 
ferric  acid.  Weisz2  claims  that  urochromogen  is  the  principal  urinary 
substance  which  causes  a  positive  diazo  reaction. 

The  reaction  may  be  taken  as  a  metabolic  symptom  of  certain  dis- 
orders, which  is  of  value  diagnostically  only  when  taken  in  connection 
with  the  other  symptoms.  The  reaction  appears  principally  in  the  urine 
in  febrile  disorders  and  in  particular  in  the  urine  in  typhoid  fever, 
tuberculosis,  and  measles.  The  reaction  has  also  been  obtained  in  the 
urine  in  various  other  disorders  such  as  carcinoma,  chronic  rheumatism, 
diphtheria,  erysipelas,  pleurisy,  pneumonia,  scarlet  fever,  syphilis, 
typhus,  etc.  The  administration  of  alcohol,  chrysarobin,  creosote, 
cresol,  dionin,  guaiacol,  heroin,  morphine,  naphthalene,  opium,  phenol, 
tannic  acid,  etc.,  will  also  cause  the  urine  to  give  a  positive  reaction. 

The  following  chemical  reactions  take  place  in  this  test: 

(a)  NaN02+HCl->HN02+NaCl. 

NH2  N 

/  /\ 

(b)  C6H4  +  HN02->C6H4          N+2H20. 

HSO3  S03 

Sulphanilic  acid  Diazo-benzenesulphonic  acid. 

1  Two  separate  solutions  should  be  prepared  Sid  mixed  in  definite  proportions  when 
needed  for  use: 

(a)  Five  grams  of  sodium  nitrite  dissolved  in  i  liter  of  distilled  water. 

(b)  Five  grams  of  sulphanilic  acid  and  50  c.c.  of  hydrochloric  acid  in  i  liter  of  distilled 
water. 

Solutions  a  and  b  should  be  preserved  in  well-stoppered  vessels  and  mixed  in  the  propor- 
tion i :  50  when  required.  Green  asserts  that  greater  delicacy  is  secured  by  mixing  the 
solutions  in  the  proportion  1:100.  The  sodium  nitrite  deteriorates  upon  standing  and 
becomes  unfit  for  use  in  the  course  of  a  few  weeks. 

2  Weisz:  Munch,  med.  Woch.,  58,  1348,  1911. 


470  PHYSIOLOGICAL   CHEMISTRY 

2.  Methylene  Blue  Reaction  (Russo).1 — To  5  c.c.  of  urine  add  4  drops  of  a  o.i  per 
cent  solution  of  methylene  blue.  In  cases  of  typhoid  fever,  measles,  smallpox  and 
certain  other  disorders  there  will  be  a  change  in  color  from  blue  to  green.  In 
normal  urine  the  blue  color  persists.  The  test  is  sometimes  used  as  a  substitute 
for  the  diazo  reaction  (see  p.  469). 

PHENOLSULPHONEPHTHALEIN  TEST  FOR  KIDNEY 
EFFICIENCY 

This  test  for  renal  function  was  devised  by  Rowntree  and  Geraghty.2 
It  depends  upon  the  injection  into  the  tissues  of  a  dyestuff  which 
is  eliminated  rapidly  by  the  normal  kidneys,  and  can  be  easily  estimated 
quantitatively  in  the  urine. 

This  dyestuff,  phenolsulphonephthalein,  is  non-irritative  to  the 
body  either  when  taken  by  mouth  or  when  injected  into  the  tissues,3 
so  that  it  does  no  harm  to  an  already  weakened  kidney. 

The  patient  upon  whom  the  test  is  to  be  performed  is  given  300-400 
c.c.  of  water  20-30  minutes  previously,  in  order  to  assure  a  free  flow 
of  urine. 

The  procedure  is  as  follows :  One  c.c.  of  a  solution  containing  6  mg.  of  phenol- 
sulphonephthalein4 per  c.c.  is  injected  intramuscularly  in  the  lumbar  region,  the 
time  of  injection  being  noted.  The  patient  is  then  catheterized  and  the  urine  as 
it  forms  thereafter  allowed  to  drop  into  a  beaker  containing  2  drops  of  25  per 
cent  NaOH.  The  appearance  of  a  red  color  in  the  alkalinized  urine  indicates 
beginning  excretion  of  the  drug,  the  normal  time  being  within  5  to  10  minutes 
after  its  injection.  Urine  is  now  collected  in  one-hour  samples.  In  patients 
with  obstruction  to  the  flow  of  urine  from  the  bladder  the  retention  catheter  is 
stoppered  and  the  urine  drawn  off  at  the  end  of  each  hour.  Other  patients  may 
simply  be  allowed  to  urinate  at  the  hourly  periods. 

To  each  hour  sample  of  urine  is  added  25  per  cent  NaOH,  drop  by  drop,  until 
the  maximum  intensity  of  color  appears.  This  color  will  remain  constant  for  an 
indefinite  period  of  time.  Each  sample  is  then  placed  in  a  1000  c.c.  volumetric 
flask  and  diluted  to  the  mark  with  distilled  water. 

Comparison  is  made  in  a  Duboscq  or  other  colorimeter  (see  p.  508)  with 
a  standard  consisting  of  3  mg.  of  phenolsulphonephthalein  in  1000  c.c.  of  solu- 
tion. The  cylinder  containing  the  standard  may  conveniently  be  placed  at  the  10 
mm.  mark.  Since  the  volume  of  each  urine  sample  is  the  same  as  that  of  the 
standard,  the  percentage  elimination  of  phenolsulphonephthalein  in  each  may  be 
easily  calculated  as  follows :  0 

1  Russo:  Riforma  med.,  No.  19,  1905. 
Peskow:  Semaine  med.,  103,  1912. 
da  Pozzo:  Gaz.  Osp.  Clin.,  35,  865,  1914. 

'Rowntree  and  Geraghty:  Jour.  Pharm.  and  Exper.  Therap.,  i,  579,  1910:  also  Arch. 
Int.  Med.,  March,  1912,  p.  284. 

3  Abel  and  Rowntree:  Jour.  Pharm.  and  Exper.  Therap.,  i,  231,  1910. 

4  This  solution  is  prepared  by  adding  0.6  gram  phenolsulphonephthalein  and  0.84  c.c. 
of  2/N  NaOH  to  enough  0.75  per  cent  NaCl  solution  to  make  100  c.c.    This  gives  the  mono- 
sodium  or  acid  salt  which  is  slightly  irritant  locally  when  injected.    It  is  necessary  to  add 
2-3  drops  more  2/N  NaOH  which  changes  the  color  to  a  bordeaux  red.     This  prepara- 
tion is  non-irritant. 


URINE  471 

Reading  of  Urine :  Reading  of  Standard ::  50 :  X. 

The  amount  of  the  drug  eliminated  normally  is  40-60  per  cent  during 
the  first  hour  and  20-25  Per  cent  during  the  second  hour,  or  a  total  of 
60-85  per  cent  for  two  hours.  The  amount  of  the  drug  excreted  has 
been  found  to  be  independent  of  the  quantity  of  urine  obtained. 
In  case  of  delayed  excretion  the  collection  of  hourly  samples  may  be 
continued  until  practically  all  of  the  drug  has  been  recovered  in  the 
urine. 

If  it  is  desired  to  test  the  function  of  each  kidney  separately, 
ureteral  catheterization  must  be  resorted  to,  the  experiment  other- 
wise being  performed  as  above  described. 

The  phenolsulphonephthalein  test  may  be  used  to  indicate  the 
amount  of  derangement  in  quantitative  functional  disturbance  of  the 
kidneys,  as  in  chronic  interstitial  and  chronic  parenchymatous  neph- 
ritis or  uremia. 

McLean1  has  very  recently  suggested  a  method  for  studying  kidney 
function  which  is  based  upon  the  relationship  between  the  urea  con- 
tent of  the  blood  and  the  rate  at  which  the  urea  is  excreted  by  the 
kidney.  It  gives  similar  values  to  the  phenolsulphonephthalein  test. 
It  has  an  advantage  in  that  it  enables  one  to  measure  kidney  function 
by  a  study  of  an  actual  normal  function  of  the  organ,  i.e.,  urea  excre- 
tion. The  method,  however,  is  more  or  less  complex. 

Mosenthal  Test  for  Kidney  Function.2 — Principle. — The  patient 
under  examination  is  placed  for  a  day  on  a  more  or  less  definite  diet 
which  should  contain  a  sufficient  quantity  of  protein,  salt,  fluid,  and 
purine  derivatives,  i.e.,  diuretic  materials  such  as  are  present  in  an 
ordinary  diet.  The  urine  is  collected  in  six  two-hour  periods  during 
the  day  and  one  twelve-hour  night  period.  These  urine  specimens 
are  analyzed  for  volume,  specific  gravity,  total  nitrogen,  and  chlorides. 

Procedure. — On  the  day  of  the  test  have  the  patient  empty  the  bladder  at 
8  A.M.  and  start  the  diet  for  the  day  which  is  selected  to  contain  approximately 
13-14  grams  of  nitrogen,  8-9  grams  of  salt,  1700-1800  c.c.  of  fluid,  and  con- 
siderable purine  material  in  meat,  soup,  tea,  and  coffee.8  No  solid  food  nor 
fluid  of  any  kind  must  be  taken  between  meals  and  especial  care  must  be  ob- 
served that  nothing  is  eaten  nor  drunk  during  the  night.  The  meals  should 
start  at  8  A.M.,  12  Noon,  and  5  P.M.  respectively. 

1  McLean:  Jour.  Am.  Med.  Ass'n,  66,  415,  1916. 

2  Mosenthal:  Boston  Med.  and  Su~g.  Jour.,  170,  245,  1914. 

3  A  diet  suitable  to  ordinary  hospital  conditions  is  given  by  Kahn:  "Functional  Diag- 
nosis," p.  260,  New  York,  1920.     It  is  emphasized  that  the  diet  need  not  be  exactly  the 
same  as  that  given  since  the  foods  found  in  the  ordinary  household  contain  sufficient  diuretic 
materials  for  the  proper  carrying  out  of  the  test.     In  private  practice  it  is  only  necessary 
to  ask  the  patient  to  eat  three  full  meals  a  day  and  write  down  the  approximate  quantities, 
as — i  cup  of  coffee,  two  slices  of  toast,  two  tablespoonfuls  of  oatmeal,  etc. 


472  PHYSIOLOGICAL  CHEMISTRY 

Collect  the  urine  punctually  at  the  end  of  every  two-hour  period  until  8 
P.M.  and  place  in  separate  bottles.  Collect  the  night  urine  from  8  P.M.  to 
8  A.M.  of  the  following  day  in  another  bottle.  Measure  the  volume  of  each 
specimen  of  urine  and  determine  in  each  case  the  specific  gravity,  total  nitrogen, 
and  total  chlorides. 

Interpretation.1 — The  test  is  of  particular  value  apparently  as 
giving  earlier  indications  of  diminished  kidney  efficiency  than  is  true 
of  other  tests  used.  It  is  sometimes  difficult  to  interpret  the  results 
obtained  in  terms  of  renal  involvement  because  of  the  influence  of 
possible  extrarenal  factors.2  In  general,  however,  the  normal  response 
is  one  in  which  the  specific  gravity  figures  vary  10  points  or  more  from 
the  highest  to  the  lowest  and  the  volume  of  the  night  urine  is  750  c.c. 
or  less.  If  the  percentage  of  nitrogen  and  sodium  chloride  in  the  night 
urine  or  in  the  highest  of  any  of  the  day  specimens  is  i  per  cent  a 
normal  condition  is  indicated.  Values  under  i  per  cent,  however, 
may  or  may  not  be  abnormal. 

When  kidney  function  becomes  involved  the  first  signs  are  usually 
demonstrated  in  the  night  urine.  The  quantity  becomes  increased  and 
the  specific  gravity  and  the  nitrogen  concentration  are  lowered.  One  or 
all  of  these  changes  from  the  normal  may  occur.  In  severe  cases  of 
chronic  nephritis  an  advanced  degree  of  functional  inadequacy  of  the 
kidney  is  indicated  by  a  markedly  fixed  and  low  specific  gravity;  a 
diminished  output  of  both  salt  and  nitrogen,  a  tendency  to  total  poly- 
uria  and  a  night  urine  showing  an  increased  volume,  low  specific  gravity, 
and  low  concentration  of  nitrogen.  Such  functional  pictures  are, 
however,  not  confined  to  nephritis.  They  are  found  frequently  in 
many  other  conditions:  pyelitis,  cystitis,  hypertrophied  prostate, 
marked  anemia,  pyelonephritis,  polycystic  kidney,  and  diabetes  in- 
sipidus.  The  following  table  taken  from  Mosenthal  shows  the  response 
of  a  normal  individual: 

1Kahn:  loc.  cit.\  Mosenthal:  Arch.  Int.  Med.,  22,  770,  1918. 
2Lyle  and  Sharlit:  Arch.  Int.  Med.,  21,  366,  1918. 
Mosenthal  and  Lewis:  Jour.  Am.  Med.  Ass'n.,  67,  933,  1916. 


URINE 


473 


Time  of  day 

Urine 

Sodium  chloride 

Nitrogen 

c.c. 

Sp.gr. 

Per  cent 

Grams 

Per  cent 

Grams 

8-10 

iS3 
156 
194 
260 
114 
238 

.016 
.019 

.012 
.014 
.O2O 
.OIO 

1.32 
1.25 
0.64 
0.77 
0.99 
0-43 

2  .02 

i-95 
1.24 

2  .OO 

M3 

1.02 

0.89 
0.74 

0-59 
0.56 

o-9S 
0.52 

.26 
•15 
•14 
.46 
.08 
1-235 

10-12  

12—2.  .  .                

2—4 

4-6  
6-8  

Total  day  

"*5 

375 

I  .O2O 

9-36 
2.36 

1.23 

7-32 
4.61 

Night,  8-8  

0.63 

Total   24  hours 

1490 
1760 



II  .72 

8.5 

II-93 
13-4 

Intake  

Balance  

+  270 



...... 

-3-« 

+  1-47 

In  addition  to  the  methods  cited  above  a  number  of  studies  of 
kidney  efficiency,  based  on  the  elimination  of  administered  urea,  have 
been  made  by  various  investigators,  among  whom  may  be  mentioned 
McCaskey,1  Addis  and  Watenabe,2  MacLean  and  De  Wesselow*  and 
Weiss.4 

1  McCaskey:  Med.  Rec.,  85,  507,  1914. 

2  Addis  and  Watenabe:  Jour.  Biol.  Chem.,  28,  251,  1916. 

3  MacLean  and  DeWesselow:  Brit.  Jour.  Exp.  Path.,  i,  i,  1920. 

4  Weiss:  Jour.  Am.  Med.  Ass'n.,  76,  298,  1921. 


CHAPTER  XXV 

URINE:  ORGANIZED  AND  UNORGANIZED 
SEDIMENTS 

THE  data  obtained  from  carefully  conducted  microscopical  exami- 
nations of  the  sediment  of  certain  pathological  urines  are  of  very  great 
importance  diagnostically.  Too  little  emphasis  is  sometimes  placed 
upon  the  value  of  such  findings. 

The  sedimentary  constituents  may  be  divided  into  two  classes, 
i.e.,  organized  and  unorganized.  The  sediment  is  ordinarily  collected 


FIG.  138. — THE  PURDY  ELECTRIC  CENTRIFUGE. 


FIG.  139. — SEDIMENT  TUBE  FOR  THE 
PURDY  ELECTRIC  CENTRIFUGE. 


for  examination  by  means  of  the  centrifuge  (Fig.  138).  An  older 
method,  and  one  still  in  vogue  in  some  quarters,  is  the  so-called  gravity 
method.  This  simply  consists  in  placing  the  urine  in  a  conical  glass 
and  allowing  the  sediment  to  settle.  The  collection  of  the  sediment  by 
means  of  the  centrifuge,  however,  is  much  preferable,  since  the  process 
of  sedimentation  may  be  accomplished  by  the  use  of  this  instrument  in  a 
few  minutes,  and  far  more  perfectly,  whereas  when  the  other  method  is 
used  it  is  frequently  necessary  to  allow  the  urine  to  remain  in  the  con- 

474 


URINE  475 

ical  glass  12-24  hours  before  sufficient  sediment  can  be  secured  for  the 
microscopical  examination. 

(a)  Unorganized  Sediments 

Ammonium  magnesium  phosphate  ("triple  phosphate"). 

Calcium  oxalate. 

Calcium  carbonate. 

Calcium  phosphate. 

Calcium  sulphate. 

Uric  acid. 

Urates. 

Cystine. 

Cholesterol. 

Hippuric  acid. 

Leucine  (?)  and  tyrosine.  v, 

Hematoidin  and  bilirubin. 

Magnesium  phosphate. 

Indigo. 

Xanthine. 

Melanin. 

Ammonium    Magnesium    Phosphate    ("Triple    Phosphate")- — 

Crystals  of  "triple  phosphate"  are  a  characteristic  constituent  of  the 
sediment  when  alkaline  fermentation  of  the  urine  has  taken  place 
either  before  or  after  being  voided.  They  may  even  be  detected  in 
amphoteric  or  slightly  acid  urine  provided  the  ammonium  salts  are 
present  in  large  enough  quantity.  This  substance  may  occur  in  the 
sediment  in  two  forms,  i.e.,  prisms  and  the  feathery  type.  The  pris- 
matic form  of  crystals  (Fig.  134,  page  426)  is  the  one  most  commonly 
observed  in  the  sediment;  the  feathery  form  (Fig.  134,  page  426)  pre- 
dominates when  the  urine  is  made  ammoniacal  with  ammonia. 

The  sediment  of  the  urine  in  such  disorders  as  are  accompanied  by 
a  retention  of  urine  in  the  lower  urinary  tract  contains  "triple  phos- 
phate" crystals  as  a  characteristic  constituent.  The  crystals  are  fre- 
quently abundant  in  the  sediment  during  paraplegia,  chronic  cystitis, 
enlarged  prostate,  and  chronic  pyelitis. 

Calcium  Oxalate. — Calcium  oxalate  is  found  in  the  urine  in  the 
form  of  at  least  two  distinct  types  of  crystals,  i.e.,  the  dumb-bell  type 
and  the  octahedral  type  (Fig.  140,  page  476).  Either  form  may  occur 
in  the  sediment  of  neutral,  alkaline,  or  acid  urine,  but  both  forms  are 
found  most  frequently  in  urine  having  an  acid  reaction.  Occasionally, 
in  alkaline  urine,  the  octahedral  form  is  confounded  with  "triple  phos- 


476 


PHYSIOLOGICAL   CHEMISTRY 


phate"  crystals.     They  may  be  differentiated  from  the  phosphate 
crystals  by  the  fact  that  they  are  insoluble  in  acetic  acid. 

The  presence  of  calcium  oxalate  in  the  urine  is  not  of  itself  a  sign  of 
any  abnormality,  since  it  is  a  constituent  of  normal  urine.  It  is  increased 
above  the  normal,  however,  in  such  pathological  conditions  as  diabetes 


M     * 


FIG.  140.— CALCIUM  OXALATE.    (Ogden.) 

mellitus,  in  organic  diseases  of  the  liver,  and  in  various  other  conditions 
which  are  accompanied  by  a  derangement  of  digestion  o/of  the  oxida- 
tion mechanism,  such  as  occurs  in  certain  diseases  of  the  heart  and 
lungs. 

Calcium  Carbonate. — Calcium  carbonate  crystals  form  a  typical 
constituent  of  the  urine  of  herbivorous  animals.     They  occur  less  fre- 


FIG.  141. — CALCIUM  CARBONATE. 


quently  in  human  urine.  The  reaction  of  urine  containing  these 
t  crystals  is  nearly  always  alkaline,  although  they  may  occur  in  ampho- 
teric  or  in  slightly  acid  urine.  It  generally  crystallizes  in  the  form 
of  granules,  spherules,  or  dumb-bells  (Fig.  141).  The  crystals  of 
calcium  carbonate  may  be  differentiated  from  calcium  oxalate  by  the 


URINE  477 

fact  that  they  dissolve  in  acetic  acid  with  the  evolution  of  carbon  dioxide 
gas. 

Calcium  Phosphate  (Stellar  Phosphate). — Calcium  phosphate  may 
occur  in  the  urine  in  three  forms,  i.e.,  amorphous,  granular,  or  crystal- 
line. The  crystals  of  calcium  phosphate  are  ordinarily  pointed,  wedge- 
shaped  formations  which  may  occur  as  individual  crystals  or  grouped 
together  in  more  or  less  regularly  formed  rosettes  (Fig.  no,  page  340). 
Acid  sodium  urate  crystals  (Fig.  143,  page  479)  are  often  mistaken  for 
crystals  of  calcium  phosphate.  We  may  differentiate  between  these 
two  crystalline  forms  by  the  fact  that  acetic  acid  will  readily  dissolve 
the  phosphate,  whereas  the  urate  is  much  less  soluble  and  when  finally 
brought  into  solution  and  recrystallized  one  is  frequently  enabled  to 
identify  uric  acid  crystals  which  have  been  formed  from  the  acid  urate 
solution.  The  clinical  significance  of  the  occurrence  of  calcium  phos- 
phate crystals  in  the  urinary  sediment  is  similar  to  that  of  "triple 
phosphate"  (see  page  426). 

Calcium  Sulphate. — Crystals  of  calcium  sulphate  are  of  quite  rare 
occurrence  in  the  sediment  of  urine.  Their  presence  seems  to  be 
limited  in  general  to  urines  which  are  of  a  decided  acid  reaction. 
Ordinarily  it  crystallizes  in  the  form  of  long,  thin,  colorless  needles  or 
prisms  (Fig.  133,  page  423)  which  may  be  mistaken  for  calcium  phos- 
phate crystals.  There  need  be  no  confusion  in  this  respect,  however, 
since  the  sulphate  crystals  are  insoluble  in  acetic  acid,  which  reagent 
readily  dissolves  the  phosphate.  As  far*  as  is  known  their  occurrence 
as  a  constituent  of  urinary  sediment  is  of  very  little  clinical  significance. 

Uric  Acid. — Uric  acid  forms  a  very  common  constituent  of  the  sedi- 
ment of  urines  which  are  acid  in  reaction.  It  occurs  in  more  varied 
forms  than  any  of  the  other  crystalline  sediments  (Plate  V,  opposite 
page  397,  and  Fig.  142),  some  of  the  more  common  varieties  of  crystals 
being  rhombic  prisms,  wedges,  dumb-bells,  whetstones,  prismatic 
rosettes,  irregular  or  hexagonal  plates,  etc.  Crystals  of  pure  uric  acid 
are  always  colorless  (Fig.  127,  page  397),  but  the  .form  occurring  in 
urinary  sediments  is  impure  and  under  the  microscope  appears  pig- 
mented,  the  depth  of  color  varying  from  yellow  to  a  dark  reddish- 
brown  according  to  the  size  and  form  of  the  crystal. 

The  presence  of  a  considerable  uric  acid  sediment  does  not,  of  neces- 
sity, indicate  a  pathological  condition  or  a  urine  of  increased  uric  acid 
content,  since  this  substance  very  often  occurs  as  a  sediment  in  urines 
whose  uric  acid  content  is  diminished  from  the  normal  merely  as  a  re- 
sult of  changes  in  reaction,  etc.  Pathologically,  uric  acid  sediments  oc- 
cur in  gout,  acute  febrile  conditions,  chronic  interstitial  nephritis,  etc. 
If  the  microscopical  examination  is  not  conclusive,  uric  acid  may  be 


478 


PHYSIOLOGICAL   CHEMISTRY 


differentiated  from  other  crystalline  urinary  sediments  from  the  fact 
that  it  is  soluble  in  alkalis,  alkali  carbonates,  boiling  glycerol,  concen- 
trated sulphuric  acid,  and  in  certain  organic  bases  such  as  ethylamine 
and  piperidin.  It  also  responds  to  the  murexide  test  (see  page  397), 
Schiff's  reaction  (see  page  398)  and  to  Folin's  phosphotungstic  acid 
reaction  (see  page  398). 

Urates. — The  urate  sediment  may  consist  of  a  mixture  of  the  urates 
of  ammonium,  calcium,  magnesium,  potassium,  and  sodium.  The 
ammonium  urate  may  occur  in  neutral,  alkaline,  or  acid  urine,  whereas 
the  other  forms  of  urates  are  confined  to  the  sediments  of  acid  urines. 
Sodium  urate  occurs  in  sediments  more  abundantly  than  the  other 


FIG.  142.  —  VARIOUS  FORMS  OF  URIC  ACID. 


i,  Rhombic  plates;  2,  whetstone  forms;  3,  3,  quadrate  forms;  4,  5,  prolonged  into 
points;  6,  8,  rosettes;  7,  pointed  bundles;  9,  barrel  forms  precipitated  by  adding  hydro- 
chloric acid  to  urine. 

urates.     There  are  two  sodium  urates,  the  mono  and  the  di,  which  may 

Na+\  "NTs  +\ 

be  expressed  thus     H+  ^C5H2^^Or  and  JJ*+  ">C5H2N4O3~.     Both 

salts  dissociate  with  the  production  of  an  alkaline  reaction,  the  alka- 
linity being  stronger  in  the  case  of  the  di-sodium  urate.  The  so-called 
quadriurate  or  hemiurate  have  no  existence  as  chemical  units.1  The 
urates  of  calcium,  magnesium,  and  potassium  are  amorphous  in 
character,  whereas  the  urate  of  ammonium  is  crystalline.  Sodium 
urate  may  be  either  amorphous  or  crystalline.  When  crystalline  it 
forms  groups  of  fan-shaped  clusters  or  colorless,  prismatic  needles  (Fig. 

1  Taylor:  Jour.  Biol.  Chem.,  i,  177,  1905. 


PLATE  VI. 


AMMONIUM  URATES,  SHOWING  SPHERULES  AND  THORN-APPLE-SHAPED  CRYSTALS. 
(From  Ogden,  after  Peyer.) 


URINE 


479 


143).  Ammonium  urate  is  ordinarily  present  in  the  sediment  in  the 
burr-like  form  of  the  "  thorn-apple "  crystal,  i.e.,  yellow  or  reddish- 
brown  spheres,  covered  with  sharp  spicules  or  prisms  (Plate  VI, 
opposite).  The  urates  are  all  soluble  in  hydrochloric  acid  or  acetic 
acid  and  their  acid  solutions  yield  crystals  of  uric  acid  upon  standing. 
They  also  respond  to  the  murexide  test.  The  clinical  significance  of 


FIG.  143. — ACID  SODIUM  URATE. 

urate  sediments  is  very  similar  to  that  of  uric  acid.  A  considerable 
sediment  of  amorphous  urates  does  not  riecessarily  indicate  a  high  uric 
acid  content,  but  ordinarily  signifies  a  concentrated  urine  having  a  very 
strong  acidity. 

Cystine. — Cystine  is  one  of  the  rarer  of  the  crystalline  urinary  sedi- 
ments.    It  has  been  claimed  that  it  occurs  more  often  in  the  urine  of 


/ 


FIG.  144. — CYSTINE.     (Ogden.) 

men  than  of  women.  Cystine  crystallizes  in  the  form  of  thin,  color- 
less, hexagonal  plates  (Fig.  26,  page  75,  and  Fig.  144)  which  are 
insoluble  in  water,  alcohol,  and  acetic  acid,  and  soluble  in  mineral 
acids,  alkalis,  and  especially  in  ammonia.  Cystine  may  be  identified 
by  burning  it  upon  platinum  foil,  under  which  condition  it  does  not 


480  PHYSIOLOGICAL   CHEMISTRY 

melt  but  yields  a  bluish-green  flame.  For  preparation  of  Cystine  see 
Chapter  IV. 

Cholesterol. — Cholesterol  crystals  have  been  but  rarely  detected  in 
urinary  sediments.  When  present  they  probably  arise  from  a  patho- 
logical condition  of  some  portion  of  the  urinary  tract.  Crystals  of 
cholesterol  have  been  found  in  the  sediment  in  cystitis,  pyelitis, 
chyluria,  and  nephritis.  Ordinarily  it  crystallizes  in  large  regular  and 
irregular  colorless,  transparent  plates,  some  of  which  possess  notched 
corners  (Fig.  63,  page  213).  Frequently,  instead  of  occurring  in  the 
sediment,  it  is  found  in  the  form  of  a  film  on  the  surface  of  the  urine. 

Hippuric  Acid. — This  is  one  of  the  rare  sediments  of  human  urine. 
It  deposits  under  conditions  similar  to  those  which  govern  the  formation 

of  uric  acid  sediments.  The  crystals, 
which  are  colorless  needles  or  prisms 
(Fig.  130,  page  406)  when  pure,  are  in- 
variably pigmented  in  a  manner  similar 
to  the  uric  acid  crystals  when  observed 
in  urinary  sediment  and  because  of  this 
fact  are  frequently  confounded  with  the 
rarer  forms  of  uric  acid.  Hippuric  acid 
©  may  be  differentiated  from  uric  acid 

FIG.  145.— CRYSTALS  OF  IMPURE      from  the  fact  that  it  does  not  respond  to 
LEUCINE.     (Ogden.)  .  .  ,  ,    . 

the  murexide  test  and  is  much  more 

soluble  in  water  and  in  ether.  The  detection  of  crystals  of  hippuric 
acid  in  the  urine  has  very  little  clinical  significance,  since  its  pres- 
ence in  the  sediment  depends  in  most  instances  very  greatly  upon 
the  nature  of  the  diet.  It  is  particularly  prone  to  occur  in  the  sedi- 
ment after  the  ingestion  of  certain  fruits  as  well  as  after  the  ingestion  of 
benzoic  acid  (see  pages  405  and  619). 

Leucine  and  Tyrosine. — Leucine  and  tyrosine  have  frequently 
been  detected  in  the  urine,  either  in  solution  or  as  a  sediment.  Neither 
of  them  occurs  in  the  urine  ordinarily  except  in  association  with  the 
others,  i.e.,  whenever  leucine  is  detected  it  is  more  than  probable  that 
tyrosine  accompanies  it.  They  have  been  found  pathologically  in 
the  urine  in  acute  yellow  atrophy  of  the  liver,  in  acute  phosphorus 
poisoning,  in  cirrhosis  of  the  liver,  in  severe  cases  of  typhoid  fever 
and  small-pox,  and  in  leukemia.  In  urinary  sediments  leucine  ordi- 
narily crystallizes  in  characteristic  spherical  masses  which  show  both 
radial  and  concentric  stria tions  and  are  highly  refractive  (Fig.  145). 
Some  investigators  claim  that  these  crystals  which  are  ordinarily  called 
leucine  are,  in  reality,  generally  urates.  This  view  point  has  become 
more  general  in  recent  years.  For  the  crystalline  form  of  pure  leucine 


URINE  481 

obtained  as  a  decomposition  product  of  protein  see  Fig.  28,  page  79. 
Tyrosine  crystallizes  in  urinary  sediments  in  the  well-known  sheaf 
or  tuft  formation  (Fig.  25,  page  75).  For  other  tests  on  leucine  and 
tyrosine  see  pages  85  and  86. 

Hematoidin  and  Bilirubin. — There  are  divergent  opinions  regard- 
ing the  occurrence  of  these  bodies  in  urinary  sediment.  Each  of  them 
crystallizes  in  the  form  of  tufts  of  small  needles  or  in  the  form  of  small 
plates  which  are  ordinarily  yellowish-red  in  color  (Fig.  62,  page  208). 
Because  of  the  fact  that  the  crystalline  form  of  the  two  substances  is 
identical  many  investigators  claim  them  to  be  one  and  the  same  body. 
Other  investigators  claim,  that  while  the  crystalline  form  is  the  same 
in  each  case,  there  are  certain  chemical  differences  which  may  be  brought 
out  very  strikingly  by  properly  testing.  For  instance,  it  has  been 
claimed  that  hematoidin  may  be  differentiated  from  bilirubin  through 
the  fact  that  it  gives  a  momentary  color  reaction  (blue)  when  nitric  acid 
is  brought  into  contact  with  it,  and,  further,  that  it  is  not  dissolved  on 
treatment  with  ether  or  potassium  hydroxide.  Pathologically,  typical 
crystals  of  hematoidin  or  bilirubin  have  been  found  in  the  urinary 
sediment  in  jaundice,  acute  yellow  atrophy  of  the  liver,  carcinoma  of 
the  liver,  cirrhosis  of  the  liver,  and  in  phosphorus  poisoning,  typhoid 
fever,  and  scarlatina. 

Magnesium  Phosphate. — Magnesium  phosphate  crystals  occur 
rather  infrequently  in  the  sediment  of  urine  which  is  neutral,  alkaline, 
or  feebly  acid  in  reaction.  It  ordinarily  crystallizes  in  elongated, 
highly  refractive,  rhombic  plates  which  are  soluble  in  acetic  acid. 

Indigo. — Indigo  crystals  are  frequently  found  in  urine  which  has 
undergone  alkaline  fermentation.  They  result  from  the  breaking 
down  of  indoxyl-sulphates  or  indoxyl-glycuronates.  Ordinarily  indigo 
deposits  as  dark  blue  stellate  needles  or  occurs  as  amorphous  particles 
or  broken  fragments.  These  crystalline  or  amorphous  forms  may  occur 
in  the  sediment  or  may  form  a  blue  film  on  the  surface  of  the  urine. 
Indigo  crystals  generally  occur  in  urine  which  is  alkaline  in  reaction, 
but  they  have  been  detected  in  acid  urine. 

Xanthine. — Xanthine  is  a  constituent  of  normal  urine  but  is  found 
in  the  sediment  in  crystalline  form  very  infrequently,  and  then  only  in 
pathological  urine.  When  present  in  the  sediment  xanthine  generally 
occurs  in  the  form  of  whetstone-shaped  crystals  somewhat  similar  in 
form  to  the  whetstone  variety  of  uric  acid  crystal.  They  may  be  dif- 
ferentiated from  uric  acid  by  the  great  ease  with  which  they  may  be 
brought  into  solution  in  dilute  ammonia  and  on  applying  heat.  Xan- 
thine may  also  form  urinary  calculi.  The  clinical  significance  of 
xanthine  in  urinary  sediment  is  not  well  understood. 
31 


482  PHYSIOLOGICAL  CHEMISTRY 

Melanin. — Melanin  is  an  extremely  rare  constituent  of  urinary 
sediments.  Ordinarily  in  melanuria  the  melanin  remains  in  solution; 
if  it  separates  it  is  generally  held  in  suspension  as  fine  amorphous 
granules. 

(b)  Organized  Sediments 
Epithelial  cells. 
Pus  cells. 

Hyaline. 

Granular. 

Epithelial. 


Casts. 


Blood. 


Fatty. 
Waxy. 
.Pus. 

Cylindroids.' 

Erythrocytes. 

Spermatozoa. 

Urethral  filaments. 

Tissue  debris. 

Animal  parasites. 

Micro-organisms. 

Fibrin. 

Foreign  substances  due  to  contamination. 

Epithelial  Cells. — The  detection  of  a  certain  number  of  these  cells 
in  urinary  sediment  is  not,  of  itself,  a  pathological  sign,  since  they 
occur  in  normal  urine.  However,  in  certain  pathological  conditions 
they  are  greatly  increased  in  number,  and  since  different  areas  of  the 
urinary  tract  are  lined  with  different  forms  of  epithelial  cells,  it  becomes 
necessary,  when  examining  urinary  sediments,  to  note  not  only  the 
relative  number  of  such  cells,  but  at  the  same  time  to  carefully  observe 
the  shape  of  the  various  individuals  in  order  to  determine,  as  far  as 
possible,  from  what  portion  of  the  tract  they  have  been  derived.  Since 
the  different  layers  of  the  epithelial  lining  are  composed  of  cells  dif- 
ferent in  form  from  those  of  the  associated  layers,  it  is  evident  that  a 
careful  microscopical  examination  of  these  cells  may  tell  us  the  par- 
ticular layer  which  is  being  desquamated.  It  is  frequently  a  most  diffi- 
cult undertaking,  however,  to  make  a  clear  differentiation  between  the 
various  forms  of  epithelial  cells  present  in  the  sediment.  If  skillfully 
done,  such  a  microscopical  differentiation  may  prove  to  be  of  very 
great  diagnostic  aid. 

The  principal  forms  of  epithelial  cells  met  with  in  urinary  sediments 
are  shown  in  Fig.  146,  page  483. 


URINE 


483 


Pus  Cells. — Pus  corpuscles  or  leucocytes  are  present  in  extremely 
small  numbers  in  normal  urine.  Any  considerable  increase  in  the 
number,  however,  ordinarily  denotes  a  pathological  condition,  gener- 
ally an  acute  or  chronic  inflammatory  condition  of  some  portion  of  the 
urinary  tract.  The  sudden  appearance  of  a  large  amount  of  pus  in  a 
sediment  denotes  the  opening  of  an  abscess  into  the  urinary  tract* 
Other  form  elements,  such  as  epithelial  cells,  casts,  etc.,  ordinarily 
accompany  pus  corpuscles  in  urinary  sediment  and  a  careful  examination 
of  these  associated  elements  is  necessary  in  order  to  form  a  correct  diag- 
nosis as  to  the  origin  of  the  pus.  Protein  is  always  present  in  urine 
which  contains  pus. 


•        *     •      •     •*  r- 

?-•&  ^cssw      J  m 


FIG.  146. — EPITHELIUM  FROM  DIFFERENT  AREAS  OF  THE  URINARY  TRACT. 
a,  Leucocyte  (for  comparison);  b,  renal  cells;  c,  superficial  pelvic  cells;  d,  deep  pelvic 
cells;  e,  cells  from  calices;/,  cells  from  ureter;  g,  g,  g,  g,  g,  squamous  epithelium  from  the 
bladder;  h,  h,  neck-of-bladder  cells;  i,  epithelium  from  prostatic  urethra;  k,  urethral  cells; 
I,  I,  scaly  epithelium;  m,  m',  cells  from  seminal  passages;  «,  compound  granule  cells;  o 
fatty  renal  cell.  (Ogden.) 

The  appearance  which  pus  corpuscles  exhibit  under  the  microscope 
depends  greatly  upon  the  reaction  of  the  urine  containing  them.  In 
acid  urine  they  generally  present  the  appearance  of  round,  colorless  cells 
composed  of  refractive,  granular  protoplasm,  and  may  frequently  exhibit 
ameboid  movements,  especially  if  the  slide  containing  them  be  warmed 
slightly.  They  are  nucleated  (one  or  more  nuclei),  the  nuclei  being 
clearly  visible  only  upon  treating  the  cells  with  water,  acetic  acid,  or 
some  other  suitable  reagent.  In  urine  which  has  a  decided  alkaline 
reaction,  on  the  other  hand,  the  pus  corpuscles  are  often  greatly  de- 
generated. They  may  be  seen  as  swollen,  transparent  cells,  which 
exhibit  no  granular  structure  and  as  the  process  of  degeneration  con- 


484 


PHYSIOLOGICAL   CHEMISTRY 


tinues  the  cell  outline  ceases  to  be  visible,  the  nuclei  fade,  and  finally 
only  a  mass  of  debris  containing  isolated  nuclei  and  an  occasional 
cell  remains. 

It  is  frequently  rather  difficult  to  make  a  differentiation  between  pus 
corpuscles  and  certain  types  of  epithelial  cells  which  are  similar  in  form. 
.Such  confusion  may  be  avoided  by  the  addition  of  iodine  solution  (I  in 
KI),  a  reagent  which  stains  the  pus  corpuscles  a  deep  mahogany-brown 
and  transmits  to  the  epithelial  cells  a  light  yellow  tint.  The  test  pro- 
posed by  Vitali  often  gives  very  satisfactory  results.  This  simply 
consists  in  acidifying  the  urine  (if  alkaline)  with  acetic  acid,  then  filter- 
ing, and  treating  the  sediment  on  the  filter  paper  with  freshly  prepared 
tincture  of  guaiac.  The  presence  of  pus  in  the  sediment  is  indicated 


FIG.  147. — Pus    CORPUSCLES.     (After    Ultzmann.} 

i,  Normal;  2,  showing  amoeboid  movements;  3,  nuclei  rendered  distinct  by  acetic  acid;  4, 
as  observed  in  chronic  pyelitis;  5,  swollen  by  ammonium  carbonate. 

if  a  blue  color  is  observed.  Large  numbers  of  pus  corpuscles  are  present 
in  the  urinary  sediment  in  gonorrhoea,  leucorrhcea,  chronic  pyelitis, 
and  in  abscess  of  the  kidney.  In  addition  to  the  usual  constituents 
found  in  leucocytes  Mandel  and  Levene1  claim  that  pus  cells  contain 
glucothionic  acid.  See  Pus  tests,  page  447. 

Casts. — These  are  cylindrical  formations,  which  originate  in  the 
uriniferous  tubules  and  are  forced  out  by  the  pressure  of  the  urine. 
The)'1  vary  .greatly  in  size,  but  in  nearly  every  instance  they  possess 
parallel  sides  and  rounded  ends.  The  finding  of  casts  in  the  urine  is 
very  important  because  of  the  fact  that  they  generally  indicate  some 
kidney  disorder;  if  albumin  accompanies  the  casts  the  indication  is 

1  Mandel  and  Levene:  Biochemische  Zeltschrift,  4,  78,  1907. 


URINE 


485 


much  accentuated.  Casts  have  been  classified  according  to  their 
microscopical  characteristics  as  follows:  (a)  hyaline,  (b)  granular,  (c) 
epithelial,  (d)  blood,  (e)  fatty,  (/)  waxy,  (g)  pus. 

(a)  Hyaline  Casts. — These  are  composed  of  a  basic  material  which 
is  transparent,  homogeneous,  and  very  light  in  color  (Fig.  148). 
In  fact,  chiefly  because  of  these  physical  properties,  they  are  the 
most  difficult  form  of  renal  casts  to  detect  under  the  microscope. 
Frequently  such  casts  are  impregnated  with  deposits  of  various  forms, 
such  as  erythrocytes,  epithelial  cells,  fat  globules,  etc.,  thus  rendering 
the  form  of  the  cast  more  plainly  visible.  Staining  is  often  resorted  to 


FIG.  148. — HYALINE  CASTS. 
One  cast  is  impregnated  with  four  renal  cells. 


in  order  to  render  the  shape  and  character  of  the  cast  more  easily 
determined.  Ordinary  iodine  solution  (I  in  KI)  may  be  used  in  this 
connection;  many  of  the  aniline  dyes  are  also  in  common  use  for  this 
purpose,  e.g.,  gentian- violet,  Bismarck-brown,  methylene-blue,  fuchsin, 
and  eosin.  Generally,  but  not  always,  albumin  is  present  in  urine 
containing  hyaline  casts.  Hyaline  casts  are  common  to  all  kidney 
disorders,  but  occur  particularly  in  the  earliest  and  recovering  stages 
of  parenchymatous  nephritis  and  interstitial  nephritis. 

(b)  Granular  Casts. — The  common  hyaline  material  is  ordinarily  the 
basic  substance  of  this  form  of  cast.  The  granular  material  generally 
consists  of  albumin,  epithelial  cells,  fat,  or  disintegrated  erythrocytes  or 


486 


PHYSIOLOGICAL  CHEMISTRY 


leucocytes,  the  character  of  the  cast  varying  according  to  the  nature 
and  size  of  the  granules  (Fig.  149,  and  Fig.  150,  page  487).  Thus 
we  have  casts  of  this  general  type  classified  as  finely  granular  and 
coarsely  granular  casts.  Granular  casts,  and  in  particular  the  finely 
granular  types,  occur  in  the  sediment  in  practically  every  kidney  dis- 
order but  are  probably  especially  characteristic  of  the  sediment  in  in- 
flammatory disorders. 

(c)  Epithelial  Casts. — These  are  casts  bearing  upon  their  surface 
epithelial  cells  from  the  lining  of  the  uriniferous  tubules  (Fig.  151, 
page  487).  The  basic  material  of  this  form  of  cast  may  be  hyaline  or 


FIG.  149. — GRANULAR  CASTS.     (After  Peyer.) 


granular  in  nature.     Epithelial  casts  are  particularly  abundant  in  the 
urinary  sediment  in  acute  nephritis. 

(d)  Blood  Casts. — Casts  of  this  type  may  consist  of  erythrocytes 
borne  upon  a  hyaline  or  a  fibrinous  basis  (Fig.  152,  page  487).     The 
occurrence  of  such  casts  in  the  urinary  sediment  denotes  renal  hemor- 
rhage and  they  are  considered  to  be  especially  characteristic  of  acute 
diffuse  nephritis  and  acute  congestion  of  the  kidney. 

(e)  Fatty-  Casts. — Fatty  casts  may  be  formed  by  the  deposition  of 
fat  globules  or  crystals  of  fatty  acid  upon  the  surface  of  a  hyaline  or 
granular  cast  (Fig.  153,  page  488).    In  order  to  constitute  a  true  fatty 
cast  the  deposited  material  must  cover  the  greater  part  of  the  surface 
area  of  the  cast.     The  presence  of  fatty  casts  in  urinary  sediment  in- 


URINE 


487 


dicates  fatty  degeneration  of  the  kidney;  such  casts  are  particularly 
characteristic  of  subacute  and  chronic  inflammation  of  the  kidney. 


FIG.  150. — GRANULAR  CASTS.  FIG.  151. — EPITHELIAL  CASTS. 

a,  Finely  granular;  b,  coarsely  granular. 

(/)  Waxy  Casts. — These  casts  possess  a  basic  substance  similar  to 
that  which  enters  into  the  foundation  of  the  hyaline  form  of  cast.     In 


FIG.  152. — BLOOD,  Pus,  HYALINE  AND  EPITHELIAL  CASTS. 
a,  Blood  casts;  b,  pus  cast;  c,  hyaline  cast  impregnated  with  renal  cells;  d,  epithelial  casts. 

common  with  the  hyaline  type  they  are  colorless,  refractive  bodies, 
but  differ  from  this  form  of  cast  in  being,  in  general,  of  greater  length 
and  diameter  and  possessing  sharper  outlines  and  a  light  yellow/color 


PHYSIOLOGICAL   CHEMISTRY 


FIG.  153.— FATTY  CASTS.     (After  Peyer.) 


FIG.  154. — FATTY  AND  WAXY  CASTS. 
a,  Fatty  casts;  b,  waxy  casts 


URINE 


489 


(Fig.  154,  page  488).  Such  casts  occur  in  several  forms  of  nephritis, 
but  do  not  appear  to  characterize  any  particular  type  of  the  disorder 
except  amyloid  disease,  in  which  they  are  rather  common. 

(g)  Pus  Casts. — Casts  whose  surface  is  covered  with  pus  cells  or 
leucocytes  are  termed  pus  casts  (Fig.  1 52,  p.  487).  They  are  frequently 
mistaken  for  epithelial  casts.  The  differentiation  between  these  two 
types  is  made  very  simple,  however,  by  treating  the  cast  with  acetic 
acid  which  causes  the  nuclei  of  the  leucocytes  to  become  plainly  visible. 
The  true  pus  cast  is  quite  rare  and  indicates  renal  suppuration. 

Cylindroids. — These  formations  may  occur  in  normal  or  pathological 
urine  and  have  no  particular  clinical  significance.  They  are  frequently 


FIG.  155. — CYLINDROIDS.     (After  Peyer.) 

mistaken  for  true  casts,  especially  the  hyaline  type,  but  they  are 
ordinarily  flat  in  structure  with  a  rather  smaller  diameter  than  casts, 
may  possess  forked  or  branching  ends,  and  are  not  composed  of  homo- 
geneous material  as  are  the  hyaline  casts.  Such  " false  casts"  may 
become  coated  with  urates,  in  which  event  they  appear  granular  in 
structure.  The  basic  substance  of  cylindroids  is  often  the  nucleo- 
protein  of  the  urine  (Fig.  155,  above). 

Erythrocytes. — These  form  elements  are  present  in  the  urinary 
sediment  in  various  diseases.  They  appear  as  the  normal  biconcave, 
yellow  erythrocyte  (Plate  IV,  opposite  page  252)  or  may  exhibit 
certain  modifications  in  form,  such  as  the  crenated  type  (Fig.  156) 
which  is  often  seen  in  concentrated  urine.  Under  different  condi- 


490  PHYSIOLOGICAL  CHEMISTRY 

tions  they  may  become  swollen  sufficiently  to  entirely  erase  the  bicon- 
cave appearance  and  may  even  occur  in  the  form  of  colorless  spheres 
having  a  smaller  diameter  than  the  original  disc-shaped  corpuscles. 
Erythrocytes  are  found  in  urinary  sediment  in  hemorrhage  of  the 
kidney  or  of  the  urinary  tract,  in  traumatic  hemorrhage,  hemorrhage 
from  congestion,  and  in  hemorrhagic  diathesis. 

Spermatozoa. — Spermatozoa  may  be  detected  in  the  urinary  sedi- 
ment in  diseases  of  the  genital  organs,  as  well  as  after  coitus,  nocturnal 
emissions,  epileptic,  and  other  convulsive,  attacks,  and  sometimes  in 
severe  febrile  disorders,  especially  in  typhoid  fever.  In  form  they  con- 
sist of  an  oval  body,  to  which  is  attached-  a  long,  delicate  tail  (Fig. 


FIG.  156. — CRENATED  ERYTHROCYTES. 

I57>  Page  491)-  Upon  examination  they  may  show  motility  or  may  be 
motionless. 

Urethra!  Filaments. — These  are  peculiar  thread-like  bodies  which 
are  sometimes  found  in  urinary  sediment.  They  may  occasionally  be 
detected  in  normal  urine  and  pathologically  are  found  in  the  sediment  in 
acute  and  chronic  gonorrhoea  and  in  urethrorrhcea.  The  ground-sub- 
stance of  these  urethral  filaments  is,  in  part  at  least,  similar  to  that  of  the 
cylindroids  (see  page  489) .  The  urine  first  voided  in  the  morning  is  best 
adapted  for  the  examination  for  filaments.  These  filaments  may  ordi- 
narily be  removed  by  a  pipette  since  they  are  generally  macroscopic. 

Tissue  Debris. — Masses  of  cells  or  fragments  of  tissue  are  frequently 
found  in  the  urinary  sediment.  They  may  be  found  in  the  sediment  in 
tubercular  affections  of  the  kidney  and  urinary  tract  or  in  tumors  of 
these  organs.  Ordinarily  it  is  necessary  to  make  a  histological  ex- 


URINE 


4QI 


animation  of  such  tissue  fragments  before  coming  to  a  final  decision  as 
to  their  origin. 

Animal  Parasites. — The  cysts,  booklets,  and  membrane  shreds 
of  echinococci  are  sometimes  found  in  the  urinary  sediments.  Other 
animal  organisms  which  are  more  rarely  met  with  in  the  urine  are  em- 
bryos of  the  Filaria  sanguinis  and  eggs  of  the  Distoma  hematobium  and 
A  scarifies.  Animal  parasites  in  general  occur  most  frequently  in  the 
urine  in  tropical  countries. 

Micro-organisms. — Bacteria  as  well  as  yeasts  and  moulds  are  fre- 
quently detected  in  the  urine.  Both  the  pathogenic  and  non-patho- 
genic forms  of  bacteria  may  occur.  The  non-pathogenic  forms  most 
frequently  observed  are  micrococcus  urea,  bacillus  urea,  and  staphylo- 
coccus  urea  liquefaciens.  Of  the  pathogenic  forms  many  have  been 


FIG.  157. — HUMAN    SPERMATOZOA. 

observed,  e.g.,  Bacterium  Coli,  typhoid  bacillus,  tubercle  bacillus,  gono- 
coccus,  bacillus  pyocyaneus,  and  proteus  vulgaris.  Yeast  and  moulds 
are  most  frequently  met  with  in  diabetic  urine. 

Fibrin. — Following  hematuria,  fibrin  clots  are  occasionally  ob- 
served in  the  urinary  sediment.  They  are  generally  of  a  semi-gelatin- 
ous consistency  and  of  a  very  light  color,  and  when  examined  under 
the  microscope  they  are  seen  to  be  composed  of  bundles  of  highly  re- 
fractive fibers  which  run  parallel. 

Foreign  Substances  Due  to  Contamination. — Such  foreign  sub- 
stances as  fibers  of  silk,  linen,  or  wool;  starch  granules,  hair,  fat,  and 
sputum,  as  well  as  muscle  fibers,  vegetable  cells,  and  food  particles,  are 
often  found  in  the  urine.  Care  should  be  taken  that  these  foreign 
substances  are  not  mistaken  for  any  of  the  true  sedimentary  con- 
stituents already  mentioned. 


CHAPTER  XXVI 
URINE:  CALCULI 

URINARY  calculi,  also  called  concretions,  or  concrements  are  solid 
masses  of  urinary  sediment  formed  in  some  part  of  the  urinary  tract. 
They  vary  in  shape  and  size  according  to  their  location,  the  smaller 
calculi,  termed  sand  or  gravel,  in  general  arising  from  the  kidney  or  the 
pelvic  portion  of  the  kidney,  whereas  the  large  calculi  are  ordinarily 
formed  in  the  bladder.  There  are  two  general  classes  of  calculi  as 
regards  composition,  i.e.,  simple  and  compound.  The  simple  form  is 
made  up  of  but  a  single  constituent,  whereas  the  compound  type  con- 
tains two  or  more  individual  constituents.  The  structural  plan  of 
most  calculi  consists  of  an  arrangement  of  concentric  rings  about  a 
central  nucleus,  the  number  of  rings  frequently  being  dependent  upon 
the  number  of  individual  constituents  which  enter  into  the  structure 
of  the  calculus.  However,  layers  quite  different  in  macroscopical 
appearance  may  be  almost  identical  in  composition.  In  case  two  or 
more  calculi  unite  to  form  a  single  calculus  the  resultant  body  will 
obviously  contain  as  many  nuclei  as  there  were  individual  calculi 
concerned  in  its  construction.  Under  certain  conditions  the  growth  of 
a  calculus  will  be  principally  in  only  one  direction,  thus  preventing 
the  nucleus  from  maintaining  a  central  location.  The  qualitative 
composition  of  urinary  calculi  is  dependent,  in  great  part,  upon  the 
reaction  of  the  urine,  e.g.,  if  the  reaction  of  the  urine  is  acid  the  calculi 
present  will  be  composed,  in  great  part  at  least,  of  substances  that  are 
capable  of  depositing  in  acid  urine,  e.g.,  uric  acid,  urates  and  calcium 
oxalate. 

According  to  Ultzmann,  out  of  545  cases  of  urinary  calculus,  uric 
acid  and  urates  formed  the  nucleus  in  about  81  per  cent  of  the  cases; 
earthy  phosphates  in  about  9  per  cent;  calcium  oxalate  in  about  6  per 
cent;  cystine  in  something  over  i  per  cent,  while  in  about  3  per  cent 
of  the  cases  some  foreign  body  comprised  the  nucleus. 

More  recent  analyses1  of  twenty-four  calculi  showed  the  nucleus  in 
75  per  cent  of  them  to  be  calcium  oxalate  (60  per  cent)  and  in  25  per 
cent  to  be  phosphate  (56  per  cent).  All  of  the  calculi  contained  some 
uric  acid  and  urates,  but  only  three  gave  more  than  10  per  cent. 

1  Kahn  and  Rosenbloom:  Jour.  Am.  Med.  Ass'n,  59,  2252,  1913. 

492 


URINE  493 

In  the  chemical  examination  of  urinary  calculi  the  most  valuable 
data  are  obtained  by  subjecting  each  of  the  concentric  layers  of  the 
calculus  to  a  separate  analysis.  Material  for  examination  may  be 
conveniently  obtained  by  sawing  the  calculus  carefully  through  the 
nucleus,  then  separating  the  various  layers,  or  by  scraping  off  from 
each  layer  (without  separating  the  layers)  enough  powder  to  conduct 
the  examination  as  outlined  in  the  scheme  (see  page  494). 
• 

Varieties  of  Calculus 

Uric  Acid  and  Urate  Calculi. — Uric  acid  and  urates  constitute  the 
nuclei  of  a  large  proportion  of  urinary  concretions.  Such  stones  are 
always  colored,  the  tint  varying  from  a  pale  yellow  to  a  brownish-red. 
The  surface  of  such  calculi  is  generally  smooth  but  it  .may  be  rough 
and  uneven. 

Phosphatic  Calculi.— Ordinarily  these  concretions  consist  prin- 
cipally of  "triple  phosphate"  and  other  phosphates  of  the  alkaline 
earths,  with  very  frequent  admixtures  of  urates  and  oxalates.  The 
surface  of  such  calculi  is  generally  rough  but  may  occasionally  be  rather 
smooth.  The  calculi  are  somewhat  variable  in  color,  exhibiting  gray, 
white,  or  yellow  tints  under  different  conditions.  When  composed  of 
earthy  phosphates  the  calculi  are  characterized  by  their  friability. 

Calcium  Oxalate  Calculi. — This  is  the  hardest  form  of  calculus 
to  deal  with,  and  is  rather  difficult  to  'crush.  They  ordinarily  occur 
in  two  general  forms,  i.e.,  the  small,  smooth  concretion  which  is  char- 
acterized as  the  hemp-seed  calculus,  and  the  medium-sized  or  large  stone 
possessing  an  extremely  uneven  surface,  which  is  generally  classed  as 
a  mulberry  calculus.  This  roughened  surface  of  the  latter  form  of 
calculus  is  due,  in  many  .instances,  to  protruding  calcium  oxalate 
crystals  of  the  octahedral  type. 

Calcium  Carbonate  Calculi. — Calcium  carbonate  concretions  are 
quite  common  in  herbivorous  animals,  but  of  exceedingly  rare  occur- 
rence in  man.  They  are  generally  small,  white,  or  grayish  calculi, 
spherical  in  form  and  possess  a  hard,  smooth  surface. 

Cystine  Calculi. — The  cystine  calculus  is  a  rare  variety  of  calculus. 
Ordinarily  they  occur  as  small,  smooth,  oval,  or  cylindrical  concretions 
which  are  white  or  yellow  in  color  and  of  a  rather  soft  consistency. 

Xanthine  Calculi. — This  form  of  calculus  is  somewhat  more  rare 
than  the  cystine  type.  The  color  may  vary  from  white  to  brownish- 
yellow.  Very  often  uric  acid  and  urates  are  associated  with  xanthine 
in  this  type  of  calculus.  Upon  rubbing  a  xanthine  calculus  it  has  the 
property  of  assuming  a  wax-like  appearance. 


494 


PHYSIOLOGICAL   CHEMISTRY 


On  Heating  the  Powder  on  Platinum  Foil,  It 

Does  not  burn 

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URINE  495 

Urostealith  Calculi. — This  form  of  calculus  is  extremely  rare. 
Such  concretions  are  composed  principally  of  fat  and  fatty  acid.  When 
moist  they  are  soft  and  elastic,  but  when  dried  they  become  brittle. 
Urostealiths  are  generally  light  in  color. 

Fibrin  Calculi. — Fibrin  calculi  are  produced  in  the  process  of  blood 
coagulation  within  the  urinary  tract.  They  frequently  occur  as  nuclei 
of  other  forms  of  calculus.  They  are  rarely  found. 

Cholesterol  Calculi. — An  extremely  rare  form  of  calculus  somewhat 
resembling  the  cystine  type. 

Indigo  Calculi. — Indigo  calculi  are  extremely  rare,  only  two  cases 
having  been  reported.  One  of  these  indigo  calculi  is  on  exhibition  in 
the  museum  of  Jefferson  Medical  College  of  Philadelphia. 

The  scheme,  proposed  by  Heller  and  given  on  page  494,  will  be 
found  of  much  assistance  in  the  chemical  examination  of  urinary  calculi. 


CHAPTER  XXVII 
URINE:  QUANTITATIVE  ANALYSIS 

IN  analyzing  a  normal  or  pathological  urine  quantitatively  for 
any  of  its  constituents  it  is  particularly  necessary  that  the  complete 
and  exact  24-hour  sample  be  obtained.  For  directions  with  regard  to 
the  collection  and  preservation  of  urine  for  analysis  see  Chapter 
XXII  on  General  Characteristics  of  Normal  and  Pathological  Urine. 
Methods  for  the  determination  of  the  specific  gravity  of  the  urine  are 
also  there  described.  Before  any  urine  is  taken  for  analysis  its  total 
volume  should  be  measured,  using  a  large  graduated  cylinder,  and  this 
volume  is  thereafter  taken  as  a  basis  for  the  calculations  of  the  daily 
output  of  the  individual  constituents  determined.  If  the  urine  be 
pathological  it  is  of  course  necessary  to  precede  its  quantitative 
analysis  by  qualitative  tests  for  the  pathological  constituents. 

PREPARATION  OF  STANDARD  ACID  AND  ALKALI  SOLUTIONS 

Principle. — Many  of  the  quantitative  methods  used  in  physiological 
chemistry  are  volumetric  or  titration  procedures.  For  these  methods 
solutions  of  accurately  known  strength  called  standard  solutions  are 
needed.  Their  strength  is  usually  expressed  in  terms  of  normality. 
A  normal  solution  is  one  which  contains  in  1000  c.c.  one  gram  of  re- 
placeable hydrogen  or  its  equivalent.  Thus  to  make  1000  c.c.  of  a 
normal  solution  of  hydrochloric  acid  (HC1),  we  would  need  36.5  grams 
of  this  acid  containing  one  gram  of  replaceable  hydrogen.  This  we 
derive  from  the  fact  that  the  atomic  weight  of  Cl  is  35.5  and  of  H  is  i, 
so  that  the  molecular  weight  of  HC1  is  36.5,  and  each  36.5  grams  of  this 
acid  contain  i  gram  of  replaceable  hydrogen.1  Sulphuric  acid  (H2SC>4) 
has  a  molecular  weight  of  98  or  (2+32+64),  but  98  grams  of  sulphuric 
acid  contain  2  grams  of  replaceable  hydrogen.  Therefore,  to  prepare 
a  normal  solution  of  this  acid,  we  must  use  one  half  of  98  or  49  grams  of 
sulphuric  (containing  one  gram  of  hydrogen)  for  1000  c.c.  of  normal 
solution.  Oxalic  acid  (H2C2O4  +  2H2O)  has  a  molecular  weight  of 
126  or  (2  +  24  +  64  +  36).  It  also  is  a  dibasic  acid  so  we  must  use 
only  one-half  of  126  or  63  grams  of  oxalic  acid  in  making  a  liter  of 
normal  solution. 

1  See  table  of  atomic  weights  on  last  page  preceding  index. 

496 


URINE  497 

A  normal  alkali  solution  is  exactly  equivalent  to  a  normal  acid 
solution,  i.e.,  'a  liter  of  the  alkali  will  neutralize  a  liter  of  the  acid. 
According  to  the  reaction  of  neutralization,  therefore,  the  36.5  grams 
of  HC1  in  a  liter  of  this  normal  acid  will  require  40.0  grams  of  sodium 
hydroxide  to  neutralize  it,  and  a  liter  of  normal  sodium  hydroxide 
.  must  contain  40.0  grams  of  the  alkali. 

HC1  +  NaOH  ->  NaCl  +  H2O 

(36.5)     (40.0)        (58.5)       (18) 

Having  prepared  solutions  of  acid  and  alkali  of  definitely  known 
strength,  it  is  then  possible  to  determine  the  strength  of  any  unknown 
acid  or  alkali  by  finding  out  how  much  of  these  standard  solutions  is 
required  to  neutralize  a  definite  volume  of  the  unknown  solution. 

In  order  to  tell  when  the  unknown  solution  has  been  exactly  neu- 
tralized, we  use  a  small  amount  of  one  of  a  class  of  substances  called 
indicators.  An  indicator  changes  color  at,  or  "hear,  the  neutral  point, 
and  this  color  change  indicates  the  end  point  of  the  titration. 

When  strong  acids  (as  HC1)  are  being  titrated  with  strong  alkalies 
(as  NaOH),  almost  any  of  the  common  indicators  is  satisfactory.  If 
weak  acids  (acetic  acid)  or  weak  bases  (as  ammonia)  are  being  titrated, 
it  is  necessary  to  be  very  careful  in  the  choice  of  an  indicator  as  all 
indicators  are  not  sufficiently  sensitive  to  those.1 

Preparation  of  N/io  Oxalic  Acid  Solution.— Weigh  accurately  a  watch  glass 
or  a  piece  of  glazed  paper.  Then  add  to  the  weights  on  the  balance  pan  3.1512 
gm.  With  a  spatula  transfer  to  the  watch  glass  enough  pure  oxalic  acid  in  the 
form  of  clear  crystals  to  counterbalance  exactly  the  weights  in  the  opposite 
pan.  Transfer  completely  to  a  250  c.c.  beaker  with  the  aid  of  a  camel's  hair 
brush.  Add  about  150  c.c.  of  distilled  water  and  stir  with  a  glass  rod  until 
dissolved,  warming  gently  if  necessary.  Transfer  every  particle  of  this  solution 
to  a  clean  500  c.c.  volumetric  flask,  rinsing  rod  and  beaker  several  times  with 
distilled  water.  Hold  under  the  tap  until  cooled  to  room  temperature.  Then 
add  distilled  water  until  the  bottom  of  the  meniscus  is  level  with  the  mark  on 
the  neck  of  the  flask  (the  lower  mark  if  there  are  two).  Insert  a  stopper  and 
mix  thoroughly  by  inverting  the  flask  again  and  again.  Transfer  to  a  clean  dry 
bottle.  Label.  This  solution  will  not  keep  indefinitely  and  is  to  be  used  only 
in  the  standardization  of  N/io  alkali. 

Preparation  of  N/io  Sodium  Hydroxide  Solution. — (a)  Preparation  of  con- 
centrated carbonate-free  sodium  hydroxide  solution. — Shake  up  about  120  gm. 
best  quality  NaOH  with  100  c.c.  of  distilled  water  in  a  300  c.c.  Erlenmeyer 
flask  (Pyrex)  to  make  a  saturated  solution.  Stopper  and  allow  to  stand  for  a 
couple  of  days  or  until  the  sodium  carbonate  settles  to  the  bottom  leaving  a  clear 
solution  of  NaOH  practically  free  from  carbonate. 

(b)  Preparation  of  a  Standard  Sodium  Hydroxide  Solution. — Measure  out 
6.3  c.c.  of  the  saturated  NaOH  solution  from  a  burette  into  a  liter  flask.  Add 

1For  a  further  consideration  of  indicators  see  Chapter  VII. 
32 


498  PHYSIOLOGICAL  CHEMISTRY 


750  c.c.  of  distilled  water  and  miy  thoroughly.  Clean  a  burette  by  allowing  it  to 
stand  filled  with  cleaning  mixture  (potassium  dichromate  and  sulphuric  acid)  for 
a  few  minutes  or  longer  if  necessary.  Empty,  rinse  several  times  with  tap 
water,  finally  with  distilled  water,  and  allow  to  drain.  If  necessary  to  use  the 
burette  before  it  is  perfectly  dry,  introduce  a  few  c.c.  of  the  NaOH  solution,  and 
invert  a  couple  of  times  to  rinse  the  burette,  discarding  this  NaOH.  Then 
fill  the  burette  with  the  alkali  solution,  making  sure  that  the  tip  contains  no  air 
bubbles,  and  run  out  solution  until  the  bottom  of  the  meniscus  is  exactly  at  o. 

Into  a  clean  Erlenmeyer  flask  (150-250  c.c.)  now  introduce  25  c.c.  of  N/io 
oxalic  acid  solution  measured  from  an  accurate,  clean  pipette,  previously  rinsed 
by  means  of  a  little  of  the  acid  solution  drawn  up  into  it.  Allow  the  pipette  to 
drain  about  15  seconds  against  the  side  of  the  flask.  Add  2-3  drops  of  a  i  per 
cent  alcoholic  solution  of  phenolphthalein. 

Now  run  in  NaOH  solution  from  the  burette,  rotating  the  flask.  Ten  c.c. 
can  be  added  quite  rapidly  ;  then  add  more  slowly,  and  finally  drop  by  drop  until 
the  last  drop  changes  the  color  of  the  solution  permanently  throughout  to  a 
definite  pink.  Taken  the  burette  reading.  Repeat  the  titration  until  two  exact 
duplicate  readings  are  obtained. 

Calculate  the  strength  of  the  NaOH  solution.  Divide  25  (the  number  of 
c.c.  of  N/io  oxalic  acid  used)  by  the  burette  reading  and  obtain  the  strength  of 
the  NaOH  in  terms  of  N/io  solution.  For  example,  if  15.6  c.c.  were  required  : 
25  -T-  15.6  =  1.603  X  o.i  =  0.1603  N. 

(c)  Preparation  of  the  N/io  NaOH  Solution.  —  Calculate  how  much  of  the 
standard  NaOH  solution  just  prepared  will  be  required  to  make  a  liter  of 
N/io  solution.  To  do  this  divide  1000  c.c.  by  the  strength  of  the  NaOH  in  terms 
of  N/io  solution.  Thus  in  the  example  cited  above:  1000  -r-  1.603  =  623.8  c.c. 
required.  Measure  out  the  exact  amount  of  alkali  required  (using  the  burette, 
pipette,  and  volumetric  flasks)  into  a  1000  c.c.  flask.  Dilute  with  distilled 
water  exactly  to  the  mark.  Mix  very  thoroughly  and  transfer  to  a  clean,  dry 
bottle  with  a  rubber  (not  glass)  stopper.  Check  the  strength  of  the  solution 
by  again  titrating  25  c.c.  portions  of  oxalic  acid  solution.1 

Preparation  of  N/io  Hydrochloric  Acid.—  Concentrated  hydrochloric  acid  is 
about  10  N  or  36.5  per  cent  HC1.  Approximately  N/io  HC1  may,  therefore,  be 
prepared  by  diluting  10  c.c.  of  the  concentrated  acid  to  i  liter  hi  a  volumetric 
flask.  This  must  be  standardized  by  titration  with  N/io  alkali,  using  preferably 
alizarin  red  as  an  indicator. 

Or  introduce  into  a  liter  flask  12  c.c.  of  concentrated  HC1  and  750  c.c.  of 
distilled  water.  Mix  well  and  titrate  10,  15,  or  25  c.c.  portions  of  the  acid  solu- 
tion with  N/io  NaOH,  using  alizarin  as  an  indicator.  Dividing  the  number  of  c.c. 
of  acid  used  by  the  number  of  c.c.  of  N/io  NaOH  required  gives  the  strength  of 
the  HC1  in  terms  of  N/io  solution.  Dividing  1000  by  this  quotient  gives  the 
number  of  c.c.  of  HC1  solution  to  be  measured  into  a  volumetric  flask  and  made 
up  to  1000  c.c. 

This  diluted  solution  will  be  N/io  HC1.  It  should  be  mixed  thoroughly  and 
25  c.c.  portions  of  it  checked  by  titration  with  the  N/io  NaOH.2 

*If  a  very  high  degree  of  accuracy  is  desired,  the  alkali  may  be  checked  against  pure  acid 
potassium  phthalate. 

2The  acid  solution  may  be  standardized  directly  in  the  following  manner:  Introduce  a 
platinum  dish  containing  very  pure  sodium  bicarbonate  or  the  highest  grade  anhydrous 
sodium  carbonate  into  a  hot  air  o^en  previously  heated  to  2oo°C.  Raise  the  temperature 


URINE  499 

Standard  acid  and  alkali  solutions  are  best  kept  in  paraffin-lined  bottles. 
The  acid  solution  is  the  more  permanent  of  the  two.  Alkali  solutions  must  be 
protected  from  the  carbonic  acid  of  the  air,  the  solution  being  best  drawn  over 
into  the  burette  by  means  of  a  siphon  tube  leading  from  the  top  of  the  burette 
to  the  interior  of  the  alkali  bottle.  The  air  inlet  through  the  stopper  of  the  bottle 
should  be  guarded  by  a  tube  containing  soda  lime. 

Acidity  by  Titration 

Folin's  Method.— Principle. — The  urine  is  titrated  with  standard 
sodium  hydroxide  solution,  using  phenolphthalein  as  an  indicator. 
Potassium  oxalate  is  added  to  precipitate  the  calcium  which  would 
otherwise  interfere  with  the  end-point  due  to  the  precipitation  of  calcium 
phosphate  on  neutralization  of  the  urine.  The  acidity  of  the  urine  as 
determined  in  this  way  is  not  a  correct  measure  of  the  true  acidity,  which 
is  dependent  upon  the  concentration  of  hydrogen  ions.  .  The  results 
obtained  do,  however,  ordinarily  show  a  certain  parallelism  with  the 
hydrogen  ion  concentration  and  are  of  value  for  comparative  purposes. 

Procedure. — Place  25  c.c.  of  urine  in  a  200  c.c.  Erlenmeyer  flask  and  add 
15-20  grams  of  finely  pulverized  potassium  oxalate  and  1-2  drops  of  a  i  per  cent 
phenolphthalein  solution  to  the  fluid.  Shake  the  mixture  vigorously  for  1-2 
minutes  and  titrate  it  immediately  with  N/io  sodium  hydroxide  until  a  faint  but 
unmistakable  pink  remains  permanent  on  further  shaking.  Take  the  burette 
reading  and  calculate  the  acidity  of  the  urine  under  examination. 

Calculation. — If  y  represents  the  number  of  cubic  centimeters  of  N/io  sodium 
hydroxide  used  and  y'  represents  the  volume  of  urine  excreted  in  24  hours,  the 
total  acidity  of  the  24-hour  urine  specimen  may  be  calculated  by  means  of  the 
following  proportion : 

25 :  y : :  y' :  x  (acidity  of  24-hour  urine  expressed  hi  cubic  centimeters  of  N/io 

sodium  hydroxide). 

Each  cubic  centimeter  of  N/io  sodium  hydroxide  contains  0.004 'gram  of 
sodium  hydroxide,  and  this  is  equivalent  to  0.0063  gram  of  oxalic  acid.  There- 
fore, in  order  to  express  the  total  acidity  of  the  24-hour  urine  specimen  in  equiva- 
lent j£ams__oijsKidiiim__h^  the  value  of  x,  as  just  determined, 
by  0.004^  or  multiply  the  value  of  x  by  0.0063  if  it  is  desired  to  express  the  total 
acidity  hi  grams  of  oxalic  acid._ 

Interpretation. — (Under  the  heading  "Interpretation"  there  will 
be  found,  in  connection  with  the  various  quantitative  methods  which 
follow,  brief  notes  as  to  the  possible  significance  of  the  results  ob- 
tained. Fur  some  further  points  (and  reference  to  literature)  see  the 
chapters  on  the  Normal  and  Pathological  Constituents  of  Urine  and 

to  27o°-28o°,  but  not  above  300° C.  Heat  for  half  an  hour,  allow  to  cool  in  a  dessicator, 
but  while  still  a  little  warm,  transfer  to  a  glass  stoppered  weighing  bottle.  Weigh  out 
rapidly  o.i  to  0.2  gm.  portions  of  the  sodium  carbonate,  dissolve  in  about  50  c.c.  of  water 
in  an  Erlenmeyer  flask,  and  titrate  using  methyl  orange  as  an  indicator.  One  hundred 
c.c.  of  N/io  acid  are  equivalent  to  0.530  gm.  of  dried  sodium  carbonate. 


5CO  PHYSIOLOGICAL   CHEMISTRY 

on  Metabolism.  Consult  text-books  on  physiological  chemistry  and 
clinical  diagnosis  for  complete  discussion).  The  acidity  of  the  urine 
expressed  in  cubic  centimeters  N/io  alkali  required  to  neutralize  the 
24-hour  output  varies  ordinarily  from  200  to  500  under  normal  con- 
ditions with  an  average  of  perhaps  350.  It  is  dependent  almost 
entirely  upon  the  diet,  being  low  on  a  vegetable  (base-forming)  diet 
and  high  on  a  diet  containing  much  meat,  rice,  whole  wheat  products, 
fruits  containing  benzoic  acid,  as  prunes  and  cranberries,  etc.  (acid- 
forming  foods).  On  the  administration. of  15  grams  of  sodium  bicar- 
bonate it  may  go  down  to  100;  the  ingestion  of  much  acid-forming 
food  may  increase  it  to  600.  In  fasting  it  may  rise  in  a  few  days  to 
800.  It  must  be  borne  in  mind  that  acidities  of  less  than  250  usually 
indicate  a  true  alkalinity  of  the  urine  inasmuch  as  phenolphthalein 
changes  in  an  alkaline  solution.  Samples  of  urine  collected  shortly 
after  a  meal  may  be  alkaline  due  to  the  so-called  "  alkaline  tide." 

Bacterial  decomposition  of  the  urea  of  the  urine  occurring  in  the 
urinary  tract  will  increase  the  amount  of  ammonia  and  decrease  the 
acidity  of  the  urine.  The  same  change  usually  occurs  in  urine  left  in 
contact  with  the  air.  The  acidity  of  the  urine  is  increased  in  acidosis, 
cardio-renal  and  certain  other  disorders.  The  acidity  of  the  urine 
may  be  somewhat  increased  by  administration  of  mineral  acids,  acid 
phosphates,  or  benzpates,  but  it  is  much  more  difficult  to  increase  than 
to  decrease  this  acidity. 

Van  Slyke  and  Palmer1  have  suggested  a  method  for  the  deter- 
mination of  organic  acids  in  urine.-  Inasmuch  as  organic  acids  other 
than  the  acetone  bodies  are  not  excreted  in  significant  amount  in 
diabetic  acidosis  this  method  may  be  used  as  an  approximate  estima- 
tion of  acetone  bodies  in  diabetic  urines. 

Hydrogen  Ion  Concentration  or  True  Acidity 

Indicator  Method  (Henderson  and  Palmer's  Adaptation  of  Soren- 
sen's  Method).2— Principle—The  reaction  of  the  urine  is  estimated 
by  matching  the  colors  produced  when  a  few  drops  of  indicator  are  added 
respectively  to  the  diluted  urine  and  to  standard  solutions  of  known 
reaction  similarly  diluted.  Similar  hydrogen  ion  concentrations 
are  indicated  by  similar  colors.  The  indicator  must  be  properly 
chosen. 

Standard  Solutions. — A  series  of  standard  solutions  of  known  hy- 
drogen ion  concentration  must  be  prepared.  The  solutions  as  indi- 
cated in  Table  I  (page  501)  are  satisfactory  for  urine  analysis.  The 

1  Van  Slyke  and  Palmer:  Jour.  Biol.  Chem.  41,  567,  1920. 

2  Henderson  and  Palmer:  Jour.  Biol.  Chem.,  13,  393,  1913. 


URINE 


501 


table  also  indicates  the  H  ion  concentration  of  each  solution,  the  figure 
given  being  the  logarithm  of  this  concentration  (PH+).  It  is  more 
convenient  and  rational  to  express  the  concentration  by  this  logarithmic 
notation.  True  H  ion  concentrations  corresponding  to  the  logarithmic 
figures  are  given  in  Table  II  (page  502). 

The  13  solutions  indicated  are  made  up  of  the  composition  indicated. 
Solutions  4  to  12  are  all  that  are  ordinarily  required  as  the  normal 
urinary  H  ion  concentrations  lie  between  4.80  and  7.50  and  pathological 
variations  are  usually  within  these  limits.  The  mean  normal  value  is 
almost  exactly  6.00. 

Procedure. — Select  eleven  250  c.c.  flasks  of  good  glass  and  indistinguishable 
in  color  and  form.  Into  each  of  ten  of  these  introduce  10  c.c.  of  the  various  stand- 
ard solutions.  Make  up  to  250  c.c.  with  distilled  water  and  add  to  each  exactly  the 
same  amount  of  an  aqueous  solution  of  sodium  alizarine  sulphonate  (10-15  drops). 
Mix  well  by  inverting.  Introduce  10  c.c.  of  the  urine  to  be  tested  into  a  similar 
250  c.c.  flask,  dilute  and  add  indicator  in  exactly  the  same  way  as  before.  Match 
the  color  of  the  diluted  urine  solution  with  one  of  the  standard  solutions.  By 
consulting  Table  II  (page  502)  determine  to  what  H  ion  concentration  this  corre- 
sponds. This  table  points  out  the  indicators  to  be  used  for  different  ranges  of 
acidity.  From  5.3-6.7  />-nitrophenol  is  satisfactory  and  is  used  in  the  same  way 
as  alizarin  except  that  it  must  be  present  in  concentration  of  0.08  per  cent. 
Neutral  red  is  used  in  the  same  way  for  acidities  from  6.7-7.5  about  1.5  c.c.  of 
the  i  per  cent  solution  being  required.  For  acidities  greater  than  5.5  methyl  red 
is  used  in  the  following  way :  10  c.c.  portions  of  the  standard  solutions  are  intro- 
duced into  carefully  selected  colorless  test-tubes  and  10  c.c.  of  urine  is  introduced 
into  another  tube.  The  standard  solutions  are  then  colored  to  match  the  urine 
by  the  addition  of  small  amounts  of  />-nitrophenol,  methyl  orange,  alizarine  or 
bismark  brown.  Then  to  standard  solutions  and  urine  add  0.15  c.c.  of  a  satu- 
rated solution  in  50  per  cent  alcohol,  of  methyl  red  and  match  the  colors.  For 
concentrations  of  7.5-9.27  or  less  undiluted  urine  is  matched  in  test-tubes  against 
undiluted  standard  solutions,  using  phenolphthalein  as  an  indicator  (without 
previous  coloration  of  standard  solution).  In  all  cases  estimations  are  made  in 
duplicate. 

TABLE  I 


No.      NaH2PO4 


Na2HPO< 


I 

o.  1000  N 

2 

o.oooi  N 

0.0480  N 

3 

o.oooi  N 

O.OI2O  N 

4 

0.0166  N 

0.0833  N 

5 

o.ooio  N 

.  0.0060  N 

6 

o.ooio  N 

0.0023  N 

PH+      '•   •  Indicator 

9.27] 

8.7    \  Phenolphthalein 

8.0   J   } 

7-48      L  Neutral  red  ) 

6.90      J 


CH3COOH         CHsCOONa 


9 

10 
ii 

12 
13 


0.0009  N 
0.0023  N 
0.0046  N 
0.0092  N 
0.0230  N 
o . 0460  N 
0.0920  N 


0.0920  N 
0.0920  N 
0.0920  N 
0.0920  N 
0.0920  N 
0.0920  N 
0.0920  N 


6.70 
6.30 
6.00 
5-70 
5-3° 
4.90 
4.70 


/>-Nitrophenol 
1  Methyl  red 


Sodium  alizarine 
sulphonate 


502  PHYSIOLOGICAL  CHEMISTRY 

TABLE  II 

Log  +  Log  + 

H  H 

4.6  2SoXio~7  6.4  4.0  Xio~7 

4.8  i6oXio-7  6.6  2.5  Xio~7 

5.0  iooXio~7  6.8  1.6  Xio~7 

5.2  63Xio~7  7.0  i.o  Xicr7 

5.4  4oXio~7  7.2  o.63Xio~7 

5.6  asXio"7  7.4  o.4oXio~7 

5-8  i6Xio~7  7.6  o.2sXio-7 

6.0  ioXio-7  7.8  o.i6Xio-7 

6.2  6.3Xio~7  8.0  o.ioXio-7 

Interpretation. — The  H  ion  concentration  of  the  urine  is  influenced 
by  the  same  factors  as  the  titratable  acidity  (see  page  499).  The 
normal  values  lie  between  4.80  and  7.50  with  a  mean  value  of  almost 
exactly  6.00.  For  vegetarians  the  mean  value  is  about  6.64.  In 
cardio-renal  disorders  the  mean  is  5.3.  In  most  pathological  conditions 
the  hydrogen  ion  concentration  is  increased. 

Determination  of  Hydrogen-Ion  Concentration  Using  the  Solutions  of  Clark 
and  Lubs.1 — The  following  indicators  are  suggested:  thymol  blue  covering  the 
range  of  P//I.2  —  2.8;  brom-phenol  blue,  2.8  —  4.6;  methyl  red,  4.4  —  6.0; 
brom-cresol  purple,  5.2  —  6.8;  brom-thymol  blue,  6.0  —  7.6;  phenol  red, 
6.8  -  8.4 ;  cresol-red,  7.2  -  &8 ;  thymol  blue,  8.0  -  9.6.  Solutions  of  0.04 
per  cent  strength  are  used  except  for  the  phenol  and  cresol  reds,  which  are  used 
in  0.02  per  cent  solution  and  the  methyl  red  in  0.02  per  cent  solution  hi  60  per 
cent  alcohol.2  About  10  drops  of  each  of  these  indicator  solutions  are  added  to 
10  c.c.  portions  of  standard  buffer  solutions  and  of  unknown  solutions  hi  test 
tubes  and  the  comparisons  made.  The  following  standard  buffer  solutions  are 
recommended  :3 

1Clark:  The  Determination  of  Hydrogen-Ions,  Baltimore,  1920. 

2These  indicators  may  be  obtained,  dry  or  in  prepared  solutions,  from  the  LaMotte 
Chemical  Products  Co.  or  Hynson,  Westcott  and  Dunning,  Baltimore,  Maryland.  Pre- 
pared and  standardized  buffer  solutions  may  also  be  obtained. 

3The  constituent  solutions  are  prepared  as  follows: 

0.2  M  potassium  chloride.  Dissolve  14.912  gm.  in  distilled  water  and  make  up  to  i 
liter.  The  salt  should  be  recrystallized  and  dried  at  about  i2o°C.  for  two  days. 

0.2  M  acid  potassium  phthalate.  Dissolve  40.828  gm.  in  distilled  water  and  make  up 
to  i  liter.  The  salt  should  be  recrystallized  from  distilled  water  and  dried  at  iio°-ii5° 
C.  for  some  hours. 

0.2  M  acid  potassium  phosphate.  Dissolve  27.232  gm.  in  distilled  water  and  make  up 
to  i  liter.  The  salt  should  be  recrystallized  from  distilled  water  and  dried  at  iio°-ii5° 
C.  for  some  hours. 

0.2  M  Boric  Acid  in  0.2  KCL  Dissolve  12.4048  gm.  of  air  dried  boric  acid  and  14.912 
gm.  pure  KC1  in  distilled  water  and  make  up  to  i  liter. 

o.  2  N  Sodium  Hydroxide.  Dissolve  100  grams  of  the  best  NaOH  in  100  c.c.  of  distilled 
water  in  an  Erlenmeyer  flask  (Pyrex).  Cover  the  mouth  of  the  flask  with  tin  foil,  and 
allow  the  solution  to  stand  overnight  till  the  carbonate  has  settled.  Cut  a  hardened 
filter  paper  to  fit  a  Buchner  funnel.  Treat  it  with  warm,  strong  (i  :  i)  NaOH  solution. 
Decant  the  soda  and  wash  the  paper  first  with  absolute  alcohol,  then  with  dilute  alcohol 
and  finally  with  targe  quantities  of  distilled  water.  Place  the  paper  on  the  Buchner  funnel 
and  apply  gentle  suction  until  the  greater  part  of  the  water  has  evaporated.  Now  pour 
the  concentrated  alkali  upon  the  middle  of  the  paper,  spread  it  with  a  glass  rod,  and  filter 
under  suction.  The  clear  solution  is  now  diluted  quickly  with  cold  distilled  water,  that 
has  recently  been  boiled  to  remove  CO2,  to  make  approximately  N  NaOH  (about  50  c.c. 
per  liter) .  Ten  c.c.  of  this  is  withdrawn  and  roughly  standardized  against  N  HC1.  It  is 
then  diluted  till  it  is  approximately  0.2  N  with  COr-free  water  and  the  solution  poured 


URINE 


503 


Group  i. — To  50  c.c.  of  M/5  KC1  add  the  indicated  number  of  c.c. 
of  M/5  HC1  and  dilute  to  200  c.c.     Indicator:  thymol  blue. 


p* 

HC1 

P* 

HC1 

p* 

HC1 

P* 

HC1 

I  .2 
1.4 

64-5 
4i-5 

1.6 
1.8 

26.3 
16.6 

2.O 

10.6 

2.2 

6.7 

Group  2. — To  50  c.c.  of  0.2  M  acid  potassium  phthalate  add  the 
indicated  number  of  c.c.  of  0.2  N  HC1  and  dilute  to  200  c.c.  Indica- 
tors: thymol  blue  and  brom-phenol  blue. 


p* 

HC1 

p* 

HC1 

P/f 

HC1 

P# 

HC1 

2.2                46  .  7O 

2.8 

26.42 

3-2 

14.70 

3-6 

5-97 

2.4 

39.60 

3-° 

20.32 

3-4 

9.90 

3-8 

2.63 

2.6 

32.95 

- 

Group  3. — To  50  c.c.  of  0.2  M  acid  potassium  phthalate  add  the 
indicated  number  of  c.c.  of  0.2  N  NaOH  and  dilute  to  200  c.c.  Indi- 
cators: brom-phenol  blue,  methyl  red,  and  brom-cresol  purple. 


P/r         NaOH 

P* 

NaOH  | 

P* 

NaOH 

P/r 

NaOH 

4-0 

0.40 

4-6 

12.15 

5-2 

29-95 

5.8 

43.00 

4.2 

3-70 

4-8 

17.70 

5-4- 

35-45 

6.0 

45-45 

4.4 

7-50 

5-o 

23-85 

5-6 

39-85 

6.2 

47.00 

Group  4. — To  50  c.c.  of  0.2  M  acid  potassium  phosphate  add  the 
indicated  number  of  c.c.  of  0.2  N  NaOH  and  dilute  to  200  c.c.  Indi- 
cators: brom-cresol  purple,  brom- thymol  blue,  and  phenol  red. 


p* 

NaOH 

Pff 

NaOH 

Pff 

NaOH 

P# 

NaOH 

5-8 

3-72 

6-4 

12.60 

7.0 

29.63 

7-6 

42.80 

6.0 

•  5-70 

6.6 

17.80 

7-2 

35-oo 

7-8 

45.20 

6.2 

8.60 

6.8 

23-65 

7-4 

39-50 

8.0 

46.80 

into  a  paraffined  bottle,  to  which  a  burette  and  soda-lime  guard  tubes  have  been  attached. 
The  solution  is  then  accurately  standardized  against  weighed  amounts  of  the  pure  acid 
potassium  phthalate.  To  do  this  accurately  weigh  up  about  1.6  gms.  of  the  salt,  dissolve 
in  about  30  c.c.  of  distilled  water,  add  phenolphthalein  and  titrate  with  the  alkali  till  a 
faint  but  distinct  and  permanent  pink  is  developed.  A  current  of  CO2  free  air  should  be 
blown  through  the  solution  during  the  titration. 

Grams  of  phthalate  used  X  1000      ...         ,.,      .  XT  ^^ 
-r  =  Normality  of  NaOH. 
204.14  X  c.c.  NaOH  required 

It  is  not  necessary  to  make  exactly  0.2  N,  but  the  true  strength  must  be  considered  in 
making  standards. 

0.2   N  Hydrochloric  Acid. — Dilute  concentrated  HC1  to  20  per  cent.    Distill,  dilute 
distillate,  and  standardize  against  the  standard  soda,  using  methyl  red  as  the  indicator. 


5°4 


PHYSIOLOGICAL   CHEMISTRY 


Group  5. — To  50  c.c.  of  0.2  M  boric  acid  in  0.2  M  KC1  add  the 
indicated  number  of  c.c.  of  0.2  N  NaOH  and  dilute  to  200  c.c.  Indi- 
cators: cresol  red  and  thymol  blue. 


i                | 

i 

p/, 

NaOH           Pff          NaOH 

Ptf 

NaOH 

?#             NaOH 

7-8 

2.61 

8-4 

8.50 

Q.O 

21.30 

9-6              36-85 

8.0 

3-97 

8.6 

12  .OO 

9.2 

26.70 

9.8              40.80 

8.2 

5-90 

8.8 

16.30 

9-4 

32.00 

10.  0                    43-90 

Total  Solids 

1.  Drying  Method. — Place  5  c.c.  of  urine  in  a  weighed  shallow  dish,  acidify 
very  slightly  with  acetic  acid  (1-3  drops),  and  dry  it  in  vacuo  in  the  presence  of  sul- 
phuric acid  to  constant  weight.     Calculate  the  percentage  of  solids  in  the  urine 
sample  and  the  total  solids  for  the  24-hour  period. 

Interpretation. — The  average  excretion  of  total  solids  by  a  normal  adult  man  is 
about  70  grams.  It  is  largely  dependent  upon  the  protein  and  salts  of  the  diet. 
It  may  be  decreased  in  severe  nephritis  due  to  impaired  excretion,  and  greatly  in- 
creased in  diabetes  with  high  sugar  elimination. 

Practically  all  the  methods  the  technic  of  which  includes  evaporation  at  an 
increased  temperature,  either  under  atmospheric  conditions  or  in  vacuo,  are  attended 
with  error. 

Shackell's  method1  which  entails  the  vacuum  desiccation  of  the  frozen  sample 
is  extremely  satisfactory  and  should  be  used  in  all  biological  work  where  the  great- 
est accuracy  is  desired. 

2.  Calculation  by  Long's  Coefficient. — The  quantity  of  solid  material  contained 
in  the  urine  excreted  for  any  24-hour  period  may  be  approximately  computed  by 
multiplying  the  second  and  third  decimal  figures  of  the  specific  gravity  by  2.6. 
This  gives  us  the  number  of  grams  of  solid  matter  in  i  liter  of  urine.     From  this  value 
the  total  solids  for  the  24-hour  period  may  easily  be  determined. 

Calculation. — If  the  volume  of  urine  for  the  24  hours  was  1120  c.c.  and  the  spe- 
cific gravity  1.018,  the  calculation  would  be  as  follows: 

(a)  18  X  2.6  =  46.8  grams  of  solid  matter  in  i  liter  of  urine. 


(b) 


46.8  X   1120 


1000 


=  52.4  grams  of  solid  matter  in  1120  c.c.  of  urine. 


Long's  coefficient  was  determined  for  urine  whose  specific  gravity  was  taken 
at  25°C.  and  is  probably  more  accurate,  for  conditions  obtaining  in  America,  than 
the  older  coefficient  of  Haeser,  2.33. 

Interpretation. — See  above. 

Total  Nitrogen 

i.  Kjeldahl  Method.2— Principle. — The  principle  of  this  method  is 
the  conversion  of  the  various  nitrogenous  bodies  of  the  urine  into  am- 

1  Shackell:  American  Journal  of  Physiology,  24,  325,  1909. 

2  There  are  numerous  modifications  of  the  original  Kjeldahl  method;  the  one  described 
here,  however,  has  given  excellent  satisfaction  and  is  recommended  for  the  determination  of 
the  nitrogen  content  of  urine. 


URINE  505 

monium  sulphate  by  boiling  with  concentrated  sulphuric  acid,  the 
subsequent  decomposition  of  the  ammonium  sulphate  by  means  of 
a  fixed  alkali  (NaOH)  and  the  collection  of  the  liberated  ammonia  in 
an  acid  of  known  strength.  Finally,  this  partly  neutralized  acid  solu- 
tion is  titrated  with  an  alkali  of  known  strength  and  the  nitrogen 
content  of  the  urine  under  examination  computed. 

Procedure. — Place  5  c.c.  of  urine  in  a  500  c.c.  long-necked  Jena  glass 
Kjeldahl  flask,  add  20  c.c.  of  concentrated  sulphuric  acid  and  about  0.2  gram 
of  copper  sulphate  and  boil  the  mixture  for  some  time  after  it  is  colorless 
(about  one  hour).  If  a  suitable  hood  or  fume  chamber  is  not  available  the 
sulphuric  acid  vapors  may  be  carried  away  by  suction.  Connect  the  outlet  tube 
of  a  2-3  liter  wash  bottle  filled  with  caustic  soda  solution  with  a  suction  pump. 
The  inlet  tube  is  connected  with  a  Folin  fume  absorption  tube  such  as  illustrated 
in  Fig.  158.  If  such  a  tube  is  not  at  hand  a  small  funnel 
may  be  attached.  The  absorption  tube  is  placed  loosely 
over  the  mouth  of  the  digestion  flask  and  a  constant  current 
of  air  drawn  through  the  apparatus. 

Allow  the  flask  to  cool  and  dilute  the  contents  with 
about  200  c.c.  of  ammonia-free  water.  Add  a  little  more 
of  a  concentrated  solution  of  NaOH  than  is  necessary  to 
neutralize  the  sulphuric  acid1  and  introduce  into  the  flask 
a  little  coarse  pumice  stone  or  a  few  pieces  of  granulated 
zinc,2  to  prevent  bumping,  and  a  small  piece  of  paraffin  to 
lessen  the  tendency  to  froth.  By  means  of  a  safety-tube 

connect  the  flask  with  a  condenser  so  arranged  that  the       _ 

.   .  ,  FIG.    158.— FOLIN 

delivery-tube  passes   into  a  vessel  containing  a  known        FUME  ABSORBER. 

volume  (the  volume  used  depending  upon  the  nitrogen 
content  of  the  urine)  of  N/io  sulphuric  acid,  using  care  that  the  end  of  the 
delivery-tube  reaches  beneath  the  surface  of  the  fluid.3  Mix  the  contents  of 
the  distillation  flask  very-  thoroughly  by  shaking  and  distil  the  mixture  until 
its  volume  has  diminished  about  one-half.  Titrate  the  partly  neutralized  N/io 
sulphuric  acid  solution  by  means  of  N/io  sodium  hydroxide,  using  congo  red  as 
indicator,  and  calculate  the  content  of  nitrogen  of  the  urine  examined. 

Calculation. — Subtract  the  number  of  cubic  centimeters  of  N/io  sodium 
hydroxide  used  in  the  titration  from  the  number  of  cubic  centimeters  of  N/io 
sulphuric  acid  taken.  The  remainder  is  equivalent  to  the  number  of  cubic  centi- 
meters of  N/io  sulphuric  acid,  neutralized  by  the  ammonia  of  the  urine.  One 
c.c.  of  N/io  sulphuric  acid  is  equivalent  to  0.0014  gram  of  nitrogen.  Therefore, 
if  y  represents  the  volume  of  urine  used  in  the  determination,  and  y'  the  number 
of  cubic  centimeters  of  N/io  sulphuric  acid  neutralized  by  the  ammonia  of  the 
urine,  we  have  the  following  proportion : 

y:  ioo::y'Xo.ooi4:  x  (percentage  of  nitrogen  hi  the  urine  examined). 

Calculate  the  quantity  of  nitrogen  in  the  24-hour  urine  specimen. 

1  This  concentrated  sodium  hydroxide  solution  should  be  prepared  in  quantity  and 
"check"  tests  made  to  determine  the  volume  of  the  solution  necessary  to  neutralize  the 
volume  (20  c.c.)  of  concentrated  sulphuric  acid  used. 

a  Powdered  zinc  may  be  substituted. 

3  This  delivery- tube  should  be  of  large  caliber  in  order  to  avoid  the  "sucking  back" 
of  the  fluid. 


506  PHYSIOLOGICAL  CHEMISTRY 

Interpretation. — An  adult  of  medium  size  on  a  mixed  diet  will  usually 
excrete  12-18  grams  of  nitrogen  per  day.  It  varies,  however,  almost 
directly  with  the  protein  ingestion  and  hence  usually  runs  parallel  to 
the  excretion  of  urea  (see  page  516).  In  a  normal  adult  the  total 
nitrogen  of  the  feces  and  of  the  urine  will  often  be  almost  exactly 
equal  to  the  total  nitrogen  of  the  food.  Such  a  condition  is  called 
"nitrogen  equilibrium.7'  The  feces  usually  contain  very  little  nitrogen. 
(See  also  Ammonia,  Creatinine,  etc.) 

Calculation  of  Percentage  Nitrogen  Distribution. — In  modern  metabo- 
lism studies  where  the  various  forms  of  nitrogen  are  determined,  in 
addition  to  the  total  nitrogen  as  yielded  by  the  Kjeldahl  method,  it  is 
customary  to  indicate  what  portion  of  the  total  nitrogen  was  present  in 
the  form  of  each  of  the  individual  nitrogenous  constituents.  These 
percentage  values  are  secured  by  dividing  the  weight  (grams)  of 
nitrogen  excreted  for  the  day  in  the  form  of  each  individual  nitrogenous 
constituent  by  the  weight  of  the  total  nitrogen  output  for  the  same 
period.  For  example,  if  the  total  nitrogen  excretion  is  9.814  grams 
and  the  excretion  of  urea-nitrogen  is  81520  grams  and  the  excretions 
of  nitrogen  in  the  forms  of  ammonia  and  creatinine  are  0.271  gram  and 
0.639  gram  respectively,  the  percentage  distribution  for  these  forms  of 
nitrogen  would  be  calculated  as  follows: 

8. 5 20  grams  urea-nitrogen  -T-  9.814  grams  total  nitrogen    =  84.3  per  cent 

0.271  gram  ammonia-nitrogen     -f-  9.814  grams  total  nitrogen    =     2. 7  per  cent 
0.639  gram  creatinine-nitrogen    •*•  9.814  grams  total  nitrogen    =     6. 5  per  cent 

Nitrogen  Partition  in  Urines  Containing  Albumin. — If  the  urine  to 
be  tested  contains  albumin  this  must  be  removed  before  an  attempt  at 
a  nitrogen  partition  is  made.  This  may  be  done  by  heating  to  boil- 
ing, acidifying  with  acetic  acid  to  coagulate  the  protein,  filtering  and 
making  up  the  filtrate  to  the  original  volume  of  the  urine.  If  very  small 
amounts  of  albumin  are  present  this  is  attended  with  difficulty.  In 
these  cases  Tracy  and  Welker1  have  suggested  the  use  of  aluminium 
hydroxide  cream.  It  apparently  removes  none  of  the  nitrogenous  con- 
stituents of  normal  urine. 

Procedure. — One  liter  of  urine  (containing  not  over  i  per  cent  of  albumin) 
is  mixed  with  one  liter  of- aluminium  hydroxide  cream2  and  filtered. 

2.  Folin-Wright  Simplified Macro-KjeldahlMethod.3— Principle  — 
The  method  differs  from  the  Kjeldahl  procedure  in  that  the  digestion 

1  Tracy  and  Welker:  Jour.  Biol.  Ghent.,  22,  55,  1915.  For  other  applications  of  alu- 
minium hydroxide  precipitation  of  colloids,  see  Welker  and  Marshall,  /.  Am.  Chem.  Soc.t 
25,  820,  1913. 

*  Aluminium  Hydroxide  Cream. — To  a  i  per  cent  solution  of  ammonium  alum  at  room 
temperature  add  a  slight  excess  of  a  i  per  cent  solution  of  ammonium  hydroxide.  Wash  by 
decantation  until  the  wash  water  shows  only  the  faintest  trace  of  residue  on  evaporation. 
Stronger  solutions  should  not  be  used. 

3Folin  and  Wright:  Jour.  Biol.  Chem.,  38,  461,  1919. 


URINE 


507 


of  the  urine  is  brought  about  by  means  of  a  mixture  of  phosphoric  and 
sulphuric  acids  aided  by  ferric  chloride,  and  that  the  liberated  ammonia 
is  distilled  without  the  use  of  a  condenser.  In  this  manner  the  time 
required  for  the  completion  of  a  determination  is  very  much  shortened. 

Procedure.—  Place  5  c.c.  of  urine  in  a  300  c.c.  Kjeldahl  flask  (Pyrex),  add 
5  c.c.  of  phosphoric-sulphuric  acid  mixture,2  2  c.c.  of  10  per  cent  ferric  chloride 
solution,  and  4  to  6  small  pebbles  or  glass  beads  to  prevent  bumping.  Boil 
vigorously  in  a  hood  over  a  microburner.3  The  burner  should  give  a  strong 
flame  and  the  top  of  the  burner  should  be  not  more  than  i  cm.  away  from  the 
bottom  of  the  flask.  In  3  or  4  minutes  the  foam  which  forms  at  first  will  entirely 
disappear  and  the  flask  will  be  filled  with  dense  white  fumes.  When  this  stage 
is  reached  (but  no  earlier)  cover  the  mouth  of  the  flask  with  a  small  watch  glass 
and  continue  the  vigorous  heating  for  2  minutes.  At 
the  end  of  2  minutes  dilute  urines  will  be  green  or  blue 
and  concentrated  urines  will  be  a  light  straw  yellow,  the 
black  carbonaceous  matter  being  completely  destroyed.4 
Turn  the  flame  very  low  and  continue  the  gentle  boiling 
process  for  2  minutes.  Remove  the  flame,  let  the  flask 
cool  for  4  to  5  minutes  (not  longer),  add  50  c.c.  of 
ammonia  free  water,  then  15  c.c.  of  saturated  sodium 
hydroxide  solution  (50  to  55  per  cent)  and  connect  the 
flask  promptly,  by  means  of  a  rubber  stopper  and 
ordinary  glass  tubing,  with  a  receiver  containing  from 
35  to  75  c.c.  of  N/io  acid  together  with  enough  water  to 
make  a  total  volume  of  150  c.c.,  and  a  drop  or  two  of 
alizarin  red.  (The  arrangement  of  the  distillation  ap- 
paratus is  shown  in  Fig.  159).  As  soon  as  connection 
with  the  receiver  is  made,  apply  the  flame  again  at  full 
force,  but  not  directly  under  the  center  of  the  flask 
until  the  acid  and  alkali  have  had  time  to  mix.  The 

contents  of  the  flask  begin  to  boil  almost  at  once  and  4  to  5  minutes  boiling  trans- 
fers all  of  the  ammonia  to  the  receiver.  Under  the  conditions  described  the 
temperature  of  the  contents  of  the  receiver  reaches  only  6s-7o°C.  Disconnect 
the  receiver  and  titrate  the  excess  of  acid  with  N/io  alkali.  If  the  distillate 
is  titrated  without  cooling  it  is  essential  that  a  faint  red  color  shall  be  accepted 
as  the  end  point.  The  color  will  deepen  on  cooling  and  if  time  permits  it  is 
better  to  cool  the  distillate  in  running  water  before  titrating. 

Calculation.—  Same  as  Kjeldahl  method  (p.  505). 

Interpretation.  —  Same  as  Kjeldahl  method  (p.  506). 


FIG.  159. — FOLIN 
WRIGHT  DISTILLATION 
APPARATUS.1 


^olin  and  Wright:  Jour.  Biol.  Chem.,  38,  461,  1919. 

2  To  50  c.c.  of  5  to  6  per  cent  copper  sulphate  solution  add  300  c.c.  of  85  per  cent  phos- 
phoric acid  and  100  c.c.  of  concentrated  sulphuric  acid. 

3  A  very  convenient  clamp  for  holding  the  Kjeldahl  flasks  in  position  is  the  one  listed  as 
No.  24598  in  Arthur  H.  Thomas  Company's  catalogue.     The  microburner  suggested  by 
Folin  is  listed  under  No.  1506  in  Eimer  and  Amend's  catalogue. 

4  This  method  as  far  as  the  destructive  digestion  is  concerned  is  primarily  intended  for 
urine  only.     It  is  not  applicable  to  highly  resistant  materials,  as  for  example  milk,  which 
cannot  be  completely  destroyed  in  6  minutes.     Urines  containing  much  sugar  belong  in 
this  class.     If  2  c.c.  of  fuming  sulphuric  acid  are  used  in  addition  to  5  c.c.  of  the  regular 
reagent  sugar  urines  are  readily  destroyed  within  the  required  heating  period  of  4  to  5 
minutes. 


r0S  PHYSIOLOGICAL   CHEMISTRY 

J  • 

3.  Folin -Farmer  Microchemical  Method.1 — Principle. — This 
method  belongs  with  the  so-called  microchemical  methods  inasmuch  as 
it  is  adapted  to  the  determination  of  amounts  of  nitrogen  in  the  neigh- 
borhood of  i  mg.  while  in  the  ordinary  Kjeldahl  procedure  30-100  mg. 
of  nitrogen  are  generally  manipulated.  One  c.c.  of  diluted  urine  is 
decomposed  with  sulphuric  acid  as  in  the  Kjeldahl  method,  the  am- 
monia formed  is  set  free  by  the  addition  of  alkali  and  carried  over  into 
an  acid  solution  by  means  of  a  current  of  air.  The  ammonia  solution 
is  then  treated  with  the  Xessler-Winkler  reagent  and  the  color  produced 
compared  with  that  of  a  standard  solution  of  an  ammonium  salt 
treated  in  the  same  way. 


FIG.  i6a — DDBOSCQ  COLOEHCETEK. 

Colorimeter. — For  this  method  as  well  as  for  a  number  of  other 
methods  commonly  used  in  urinary  and  blood  analysis  an  instrument 
known  as  a  colorimeter  is  required.  Through  its  aid  we  are  able  ac- 
curately to  measure  the  respective  depths  of  color  in  two  solutions  and 
hence  to  calculate  the  comparative  amounts  of  substances  which  form 
colored  compounds  in  a  quantitative  manner.  The  most  satisfactory 
instrument  for  this  purpose  is  the  Duboscq  colorimeter  (see  Fig.  160, 
above).  This  enables  the  two  colored  solutions  to  be  compared  in 
1  Folin  and  Farmer,-  Jour.  Bid.  Ckcm.,  u,  493,  1912. 


URINE 


509 


the  same  optical  field  and  with  a  degree  of  accuracy  of  about  i  per 
cent.  The  later  type  of  the  Duboscq  colorimeter  with  cylinders  instead 
of  prisms  movable  is  to  be  preferred,  particularly  as  this  type  may  be 
readily  adapted  to  the  comparison  of  cloudy  solutions  or  suspensions, 
the  instrument  thus  modified  being  called  a  nephelometer  (see  Fig.  94, 
page  295).  In  this  later  form  of  colorimeter  the  depths  of  the  colored 
solutions  through  which  the  light  passes  are  regulated  by  raising  or 
lowering  the  cups  and  are  accurately  indicated  in  millimeters  on  a 
vernier  scale  at  the  back  of  the  instrument.  The  standard  solution  is 
placed  at  any  convenient  depth  and  the  color  of  the  solution  to  be  ex- 
amined is  matched  with  it  by  raising  or  lowering  cups.  When  the  color 


FIG.  161. — BOCK  BEN-EDICT  COLORIMETER  ILLUSTRATIONS   FROM  MYERS.    "PRACTICAL 
CHEMICAL  ANALYSIS  OP  BLOOD,"*  ST.  Louis,  1921. 

is  of  the  same  intensity  as  the  standard  the  depth  of  the  solution  is 
read.  The  amounts  of  the  colored  substance  in  solution  are  inversely 
proportional  to  the  depths  of  the  columns  of  fluid.  Thus  if  the  standard 
is  set  at  10  mm.  and  the  solution  under  examination  has  the  same  color 
density  at  20  mm.  the  latter  has  just  one-half  the  concentration  of  the 
standard. 

A  large  number  of  other  colorimeters  have  been  devised  and 
may  be  used  in  place  of  the  Duboscq.  Among  these  are  the  Kriise 
model  of  the  Duboscq,  the  Hellige,  the  Bock-Benedict  and  the  Kober. 
A  simple  colorimeter,  costing  only  about  one  dollar,  has  been  devised 
and  used  with  considerable  success  by  Peebles  and  Lewis.1  It  is 
claimed  to  compare  favorably  in  accuracy  with  other  colorimeters  and 
to  be  applicable  to  clinical  and  student  use.  A  relatively  cheap 
although  accurate  colorimeter  has  been  developed  by  Bock  and  Bene- 
dict2 in  which  the  place  of  costly  prisms  is  taken  by  mirrors  (See  Fig. 
161).  Kober  has  devised  a  combined  colorimeter  and  nephelometer 

1  Peebles  and  Le\ns:  /.  Am.  Ifed.  Ass'n.,  70,  679,  1918. 

*  Bock  and  Benedict:  Jour.  Biol.  Chem.,  33,  xix,  1918;  35,  227,  1918. 


PHYSIOLOGICAL   CHEMISTRY 


which  may  be  obtained  in  this  country  (see  page  297).  For  merely 
approximate  determinations  the  color  comparisons  may  be  made 
directly  with  a  series  of  colored  standards  of  varying  strengths  made 
up  in  exactly  similar  test-tubes  or  small  flasks.  Myers1  has  suggested 
a  satisfactory  form  of  test-tube  instrument  (see  Fig.  162). 

Procedure.— Introduce  5  c.c.  of  urine  into  a  50  c.c.  volumetric  flask  if  the 
specific  gravity  of  the  urine  is  over  1018,  or  into  a  25  c.c.  flask  if  the  specific 
gravity  is  less  than  ioi8.2  Fill  the  flask  to  the  mark 
with  distilled  water  and  invert  it  several  times  in 
order  to  guarantee  thorough  mixing.  Transfer  i  c.c.3 
of  the  diluted  urine  to  a  large  (20-25  mm.  X  200  mm.) 
Jena-glass  test-tube.  Add  to  this  i  c.c.  of  concen- 
trated sulphuric  acid,  i  gram  of  potassium  sulphate, 
i  drop  of  5  per  cent  copper  sulphate  solution  and  a 
small,  clean,  quartz  pebble  or  glass  bead.  (The 
pebble  or  bead  is  added  to  prevent  bumping.)  Boil 
the  mixture  over  a  micro-burner4  for  about  six 
minutes,  i.e.,  about  two  minutes  after  the  mixture  has 
become  colorless.  Allow  to  cool  until  the  digestion 
mixture  begins  to  become  viscous.  This  ordinarily 
takes  about  three  minutes,  but  hi  any  event  the 
mixture  must  not  be  permitted  to  solidify.  Add 
about  6  c.c.  of  water  (a  few  drops  at  a  time,  at  first, 
then  more  rapidly)  to  prevent  solidification.  To  this 
acid  solution  add  an  excess  of  sodium  hydroxide 
(3  c.c.  of  a  saturated  solution  is  sufficient)  and 
aspirate  the  liberated  ammonia  by  means  of  a  rapid 
air  current5  into  a  volumetric  flask  (100  c.c.)  contain- 
ing about  20  c.c.  of  ammonia-free  water  and  2  c.c. 
of  N/io  hydrochloric  acid  (see  Figs.  163  and  164, 
page  511).  The  air  current  should  be  only  moder- 
ately rapid  for  the  first  two  minutes  but  at  the  end 
of  this  two-minute  period  the  current  should  be  run 
at  its  maximum  speed  for  an  interval  of  eight  minutes. 

Disconnect  the  flask,  dilute  the  contents  to  about  60  c.c.  with  ammonia- 
free  water  and  dilute  similarly  i  mg.  of  nitrogen  hi  the  form  of  ammonium  sul- 

^Myers:  Jour.  Lab.  and  Clin.  Med.  i,  178,  1916. 

8  The  purpose  is  to  so  dilute  the  urine  that  i  c.c.  of  the  diluted  fluid  shall  contain  0.75- 
1.5  mg.  of  nitrogen. 

3  This  measurement  should  be  made  by  means  of  a  modified  Ostwald  pipette  (see  Ost- 
wald-Luther:    Physiko-Chemische  Messungen,  2d.  ed.,  p.  135).    Such  pipettes  may  be 
obtained  from  Eimer  and  Amend,  New  York. 

4  A  type  of  burner  which  has  proven  satisfactory  is  Eimer  and  Amend's  No.  2587. 

6  Either  a  vacuum  pump  or  compressed  air  or  a  force  pump  may  be  used.  The  com- 
pressed air  method  is  rather  the  more  convenient  inasmuch  as  the  ammonia  may  be  col- 
lected directly  in  a  volumetric  flask.  Inasmuch  as  the  necks  of  such  flasks  (100  c.c.)  are 
not  large  enough  to  permit  of  the  use  of  a  two-hole  rubber  stopper  when  suction  is  used, 
the  ammonia  should  be  collected  in  one  of  the  Jena  test-tubes  previously  described  which 
contains  2  c.c.  of  N/io  hydrochloric  acid  and  about  5  c.c.  of  ammonia-free  water.  The  am- 
monium salt  is  then  transferred  to  the  volumetric  flask  with  40-50  c.c.  of  water  and  Nes- 
slerized  as  described. 


FIG.  162.— Myers  Test- 
tube  Colorimeter.  From 
Myers,  "Practical  Chemical 
Analysis  of  Blood,"  St. 
Louis,  1921. 


URINE 


phate1  in  a  second  volumetric  flask.  Nesslerize  both  solutions  as  nearly  as 
possible  at  the  same  time  with  5  c.c.  of  Nessler-Winkler  solution2  diluted,  imme- 
diately before'using,  with  about  25  c.c.  of  ammonia-free  water  to  avoid  turbidity. 
Immediately  fill  the  two  flasks  to  the  mark  with  ammonia-free  water,  mix  well 


FIG.  163.  FIG.  164. 

FIGS.  163  AND  164. — FORMS  OF  APPARATUS  USED  IN  METHODS  OF  FOLIN  AND  ASSOCI- 
ATES FOR  DETERMINATION  OF  TOTAL  NITROGEN,  UREA  AND  AMMONIA.  (From  Jour.  Biol. 
Chem.  vol.  n,  1912.) 

and  determine  the  relative  intensity  of  the  two  colors  by  means  of  a  Duboscq 
colorimeter.8 

1  Care  should  be  taken  to  secure  the  pure  salt.    All  ammonium  salts  contain  pyridine 
bases  which  titrate  like  ammonia  but  do  not  react  with  Nessler's  reagent.    Pure  ammonium 
sulphate  may  be  prepared  by  decomposing  a  high-grade  ammonium  salt  with  sodium  hy- 
droxide and  passing  the  liberated  ammonia  into  pure  sulphuric  acid.    The  salt  is  then  pre- 
cipitated by  means  of  alcohol,  then  brought  into  solution  in  water  and  re-precipitated  by 
alcohol.    The  final  product  should  be  dried  in  a  desiccator  over  sulphuric  acid.     Dr.  H.L. 
Emerson  of  Boston  prepares  a  salt  which  is  very  satisfactory  for  use  in  this  method. 
According  to  Bock  and  Benedict,  Kahlbaum's  "Zur  Analyse"  ammonium  chloride  is 
satisfactory. 

2  Chem.  Zeit.,  1899,  p.  541.    The  Nessler-Winkler  solution  has  the  following  formula: 

Mercuric  iodide 10  grams. 

Potassium  iodide 5  grams. 

Sodium  hydroxide 20  grams. 

Water 100  c.c. 

The  mercuric  iodide  is  rubbed  up  in  a  small  porcelain  mortar  with  water,  then  washed 
into  a  flask  and  the  potassium  iodide  added.  The  sodium  hydroxide  is  dissolved  in  the 
remaining  water  and  the  cooled  solution  added  to  the  above  mixture.  The  solution  cleared 
by  standing  is  preserved  in  a  dark  bottle. 

The  25  c.c.  portion  of  the  diluted  reagent  should  be  added  about  one-third  at  a  time  to 
the  contents  of  the  flask.  It  is  very  essential  that  the  dilution  of  the  reagent  takes  place 
immediately  preceding  its  use,  inasmuch  as  the  diluted  reagent  deteriorates  in  a  few  minutes  as 
is  indicated  by  the  formation  of  a  brick-red  precipitate.  Fortunately  the  reagent  does  not 
decompose  in  this  manner  in  the  presence  of  the  ammonium  salt. 

3  The  standard  may  be  set  at  any  desired  depth  but  a  very  satisfactory  depth  is  20  mm. 
The  depth  should  be  uniform  throughout  any  series  of  comparative  tests. 


512 


PHYSIOLOGICAL  CHEMISTRY 


The  color  of  the  unknown  should  be  adjusted  to  that  of  the  standard  both  from 
above  and  below  the  level  of  the  latter.  The  matching  of  the  colors  is  ordinarily 
very  easy.  It  is  desirable  to  make  the  readings  by  diffused  daylight  if  possible. 
If  electric  light  must  be  used,  a  sheet  of  smooth  white  paper  should  be  interposed 
between  the  colorimeter  and  the  source  of  light. 

Calculation. — The. reading  of  the  standard  divided  by  the  reading  of  the  un- 
known gives  the  nitrogen  hi  milligrams  in  the  volume  of  the  urine  taken.  Calcu- 
late the  total  nitrogen  output  for  the  24-hour  period. 

Interpretation. — See  page  506. 

4.  Bock  and  Benedict's  Modification  of  the  Folin-Farmer  Procedure. — 
Bock  and  Benedict1  have  found  distillation  of  the  ammonia  more  accurate  than 


FIG.  165. — BOCK  AND  BENEDICT  APPARATUS. 

aspiration.  They  connect  the  large  Jena  test-tube  in  which  the  digestion  was 
carried  out  with  a  small  Liebig  condenser  (made  from  a  piece  of  glass  tubing 
30  by  150  mm.  with  two-hole  rubber  stoppers  at  each  end  through  which  pass 
the  inlet  and  outlet  tubes  and  the  condenser  tube  itself).  See  Fig.  171.  The 
lower  end  of  the  condenser  is  connected  with  a  glass  tube  (or  better  an  old  pipette, 
to  prevent  back  suction)  which  reaches  nearly  to  the  bottom  of  the  volumetric 
flask  used  as  a  receiver.  The  distillation  tube  also  has  a  two-hole  rubber  stop- 
per. It  is  connected  with  the  condenser  and  also  carries  a  long  straight  tube 
which  reaches  nearly  to  the  bottom  of  the  test-tube,  and  is  closed  above  with  a 
piece  of  rubber  tubing  and  a  pinch-cock.  The  digestion  is  carried  out  just  as  in 
the  Folin-Farmer  method  (see  page  508)  and  when  partially  cool  7  c.c.  of  water 
are  added.  Into  the  long  tube  passing  through  the  stopper  suck  3  c.c.  of  satu- 
rated sodium  hydroxide  solution  and  close  the  pinch-cock.  Insert  the  stopper, 
connect  with  the  condenser  and  allow  the  alkali  to  run  into  the  test-tube.  The 
fluids  are  mixed  by  blowing  a  few  bubbles  of  air  through  the  apparatus.  The 
test-tube  is  then  heated  to  vigorous  boiling  (over  a  large  free  flame),  the  distilla- 
tion being  continued  until  a  separation  of  salts  occurs  in  the  test-tube  and  the 
mixture  begins  to  bump.  This  distillation  requires  about  two  minutes.  The 

1  Bock  and  Benedict:  Jour.  Biol.  Chem.,  20,  47,  1915.  -\ 


URINE 


513 


test-tube  is  then  disconnected  from  the  condenser  and  the  latter  washed  down 
with  a  few  cubic  centimeters  of  water.  The  liquid  in  the  receiving  flask  is 
diluted  and  Nesslerized  as  in  the  FoUn -Farmer  method  (see  page  508). 

Bock  and  Benedict,  while  holding  the  distillation  procedure  to  be 
more  accurate  than  aspiration,  do  not  consider  that  the  colorimetric 
method  is  equivalent  to  the  standard  Kjeldahl  procedure  in  accuracy 
or  reliability,  although  usually  it  agrees  with  the  latter  method  within 
about  2-3  per  cent,  and  is  indispensable  where  very  small  amounts  of 
nitrogen  are  to  be  determined.  According  to  Folin1  and  others  the 
method  is  capable  of  greater  accuracy  than  this,  and  the  aspiration 
procedure  gives  satisfactory  results.  The  method  should  be  checked 
up  carefully  by  each  new  learner  of  the  method,  using  pure  solutions. 
Outside  air  is  better  than  laboratory  air  for  aspiration  purposes. 
Care  is  needed  in  using  the  pipettes,  which  should  be  of  the  Ostwald 
type  and  accurate.  In  using  them  allow  the  pipette  to  drain  against 
the  side  of  the  vessel  for  10  seconds  and  then  blow  out  clean  so  that 
nothing  is  left  behind  in  the  tip.  The  reagents  used  must  be  as  free 
as  possible  from  ammonia  and  must  be  checked  up,  particularly  the 
sulphuric  acid  and  potassium  sulphate.  Those  who  have  trouble  in 
using  a  colorimeter  may  substitute  titration  with  N/5O  hydrochloric 
acid  using  alizarin,  or  better  methyl  red,  as  an  indicator. 

Direct  Nesslerization  Method  of  Folin  and  Denis.2 — Principle. — A 
small  amount  of  urine  is  digested  with  a.  mixture  of  sulphuric  and 
phosphoric  acids  to  destroy  the  organic  matter,  the  digestion  mixture 
treated  directly  with  Nessler's  reagent  and  compared  with  a  standard 
ammonia  solution  also  Nesslerized. 

Procedure. — This  determination  requires  0.7  to  1.5  mg.  of  nitrogen. 
Dilute  5,  10  or  20  c.c.  of  urine  to  100  c.c.,  mix  and  with  an  Ostwald 
pipette  transfer  i  c.c.  of  the  diluted  urine  to  a  large  hard  glass  test  tube. 
With  an  ordinary  pipette  add  i  c.c.  of  the  phosphoric-sulphuric  acid- 
copper  sulphate  mixture3  together  with  a  small  pebble,  to  prevent 
bumping.  Heat  over  a  micro  burner  until  the  water  is  driven  off  and 
fumes  become  abundant  within  the  tube.  This  should  take  place  in 
about  two  minutes.  When  filled  with  fumes  close  the  mouth  of  the 
test  tube  with  a  watch  glass  and  continue  the  boiling  at  such  a  rate 
that,  the  tube  remains  filled  with  fumes  yet  almost  none  escape.  With- 
in two  minutes  after  the  mouth  of  test  tube  was  closed  the  contents 
should  become  clear,  and  bluish  or  light  green.  Continue  the  gentle 

1  Folin:  Jour.  Biol.  Chem.,  21,  195,  1915. 

2J7olin  and  Denis:  /.  Biol.  Chem.,  26,  486,  1916. 

3Made  by  mixing  50  c.c.  of  5  per  cent,  copper  sulphate  solution  with  300  c.c.  of  85  per 
cent  phosphoric  acid  and  then  adding  100  c.c.  of  concentrated  sulphuric  acid  free  from 
ammonia.  Keep  well  covered. 

33 


514  PHYSIOLOGICAL   CHEMISTRY 

boiling  for  30  to  60  seconds,  longer,  provided,  however,  that  the  total 
boiling  period,  with  test  tube  closed,  must  not  be  less  than  two  minutes. 
Remove  the  flame  and  let  cool  for  a  little  less  than  two  minutes,  then 
add  water.  Rinse  the  hot  digestion  mixture  (sometimes  turbid  from 
silica)  into  a  200  c.c.  volumetric  flask,  using  for  this  purpose  about 
125  c  c..of  water. 

Transfer  10  c.c.  of  standard  ammonium  sulphate  so!ution  containing 
i  mg.  of  nitrogen  into  another  200  c.c.  volumetric  flask.  Add  i 
c.c.  of  the  concentrated  phosphoric-sulphuric  acid  mixture,  to  balance 
the  acid  in  the  unknown,  and  dilute  to  a  volume  of  about  150  c.c. 
When  both  flasks  are  thus  ready  give  each  flask  a  whirl  and  add  30  c.c. 
of  Nessler's  reagent.  Shake  a  little  more  and  dilute  both  flasks  to  the 
200  c.c.  mark. 

If  the  unknown  Nesslerized  digestion  mixture  is  turbid,  centrifuge 
a  portion,  giving  a  crystal  clear  fluid  above  a  white  sediment  (silica). 
If  the  sediment  is  colored  the  Nesslerization  was  not  successful  and  the 
determination  must  be  discarded.  Compare  unknown  and  standard 
in  a  colorimeter. 

Reading  Standard 
Calculation.-Reading  rf  Unknown  =  mg.  of  nitrogen  m  amount  of 

urine  used.  Calculate  percentage  of  nitrogen  and  daily  output  in 
grams. 

Urea 

i.  Urease  Methods. — Principle. — These  methods  depend  upon  the 
principle  that  the  enzyme  urease  is  able,  at  ordinary  temperatures,  to 
transform  urea,  quickly  and  completely,  into  ammonium  carbonate. 
Takeuchi1  in  1909  discovered  the  presence  of  this  enzyme  in  the  soja 
or  soy  bean.  The  application  of  this  enzyme  to  the  determination 
of  urea  in  urine,  blood,  etc.,  was  first  proposed  by  Marshall,2  whose 
methods  have  been  modified  by  Van  Slyke  and  Cullen.3  These  latter 
investigators  prepared  a  permanent  preparation  of  the  enzyme,  in  a 
water-soluble  form,  the  use  of  which  makes  more  convenient  the  rapid 
and  accurate  determination  of  urea  in  urine,  blood  and  other  biological 
fluids. 

The  urease  method  is  probably  the  most  satisfactory  of  all  methods 
for  the  determination  of  urea.  Other  nitrogenous  constituents  such 
as  allantoin  are  not  decomposed  by  urease.  The  method  involves  no 

1  Takeuchi:  Journ.  Coll.  Agr.,  Tokyo,  1909,  Part  i. 

2  Marshall,  E.  K.,  Jr.:  /.  Biol.  Chem.,  14,  283,  1913;  15,  495,  1913;  15,  487,  1913;  17, 
351,  1914. 

3  Van  Slyke  D.  D.,  and  Cullen,  G.  E.:  /.  Am.  Med.  Ass'n,  62,  1558,  1914.     See,  also, 
/.  Biol.  Chem.,  19,  141,  1914. 


URINE 


515 


carefully  regulated  heating  procedures,  and  is  applicable  to  diabetic 
urines. 

The  procedure  for  the  determination  in  urine  consists  in  treating 
the  urine  sample  with  urease,  aerating  the  ammonia  formed  into  fiftieth- 
normal  acid,  and  titrating  the  excess  of  acid  with  fiftieth-normal 
alkali.  (For  colorimetric  procedure  see  page  517.) 

Preparation  of  Solid  Urease.1 — Digest  one  part  of  soy  bean  meal  with  five  parts 
of  water  at  room  temperature,  with  occasional  stirring,  for  an  hour,  and  clear  the  solu- 
tion by  filtration  through  paper  pulp  or  centri- 
fugation.  Pour  this  extract  slowly,  with  stirring, 
into  at  least  10  volumes  of  acetone.  The  ace- 
tone dehydrates  the  enzyme  preparation.  Filter, 
dry  in  vacuum,  and  powder.  The  activity  of 
the  preparation  is  retained  indefinitely.  Thus 
prepared  it  is  not  perfectly  soluble  in  water,  but 
this  fact  interferes  in.no  way  with  its  use. 

Standardization  of  the  Enzyme  Preparation. 
— Make  up  accurately  a  3  per  cent  solution  of 
pure  urea.  Treat  this  solution  exactly  as  the 
urine  is  treated  in  the  following  method,  using 
%  c.c.  of  the  solution.  The  ammonia  formed 
should  neutralize  25  c.c.  of  N/5o  acid.  If  it  does 
so  the  preparation  is  of  sufficient  strength  to  use 
as  indicated.  If  not,  more  of  the  preparation 
must  be  used  for  a  determination. 

The  ground  soy  bean  may  also  be  used 
directly  in  this  determination.  It  should  pass 
through  a  2o-mesh  sieve.  Rose  and  Coleman  for 
their  micro-procedure  (see  below)  use  0.2-0.4  gram  of  bean  flour  acting  in  a 
water-bath  at  50-60°  for  five  minutes.  In  their  macro-method,  using  5  c.c.  of 
urine  they  dilute  with  30  c.c.  of  water  warmed  to  50-60°  and  then  add  5  grams 
of  the  soy  bean  flour  and  let  stand  for  30  minutes.  They  then  add  5  c.c.  of 
saturated  sodium  carbonate  solution  and  aerate  as  usual. 

(a)  Procedure  of  Van  Slyke  and  Cullen. — Dilute  5  c.c.  of  urine  to  50  c.c.  with 
ammonia-free  water.  Measure  5  c.c.  of  the  diluted  urine  into  Tube  "A"  (see 
Fig.  1 66),  add  i  drop  of  caprylic  alcohol  (to  prevent  frothing),  and  i  c.c. 
of  enzyme  solution.2  Close  "A"  with  stopper  shown  in  figure,  and  let  the  tube 
stand  15  minutes  for  the  enzyme  to  act.  Measure  into  Tube  "B"  25  c.c.  of  N/SO 
HC1  or  H2SO4.  Add  i  drop  of  caprylic  alcohol  and  i  drop  of  a  i  per  cent  alizarin 
solution,3  as  indicator.  Connect  "A"  and  "B"  as  shown  in  the  figure.  At  the 

xVan  Slyke  and  Cullen:  Jour.  Biol.  Chem.,  19,  211,  1914.  Satisfactory  preparations 
of  Urease  in  powder  or  tablet  form  may  be  obtained  from  the  Arlington  Chemical  Company, 
Yonkers,  N.  Y.,  and  from^Hynson,  Westcott  and  Dunning,  Baltimore. 

2  The  enzyme  solution  is  prepared  by  dissolving  2  grams  of  the  enzyme  preparation,  0.6 
gram  of  dipotassium-hydrogen  phosphate,  and  0.4  gram  of  monopotassium-dihydrogen 
phosphate  in  10  c.c.  of  water.     Solution  is  aided  by  stirring  with  a  glass  rod.    The  slightly 
opalescent  solution  should  be  covered  with  toluol  and  may  be  kept  for  two  weeks  without 
losing  activity. 

3  Folin  states  that  methyl  red  is  preferable  to  alizarin  for  ammonia  titrations. 


FIG.  166. — VAN  SLYKE  AND 
CULLEN  APPARATUS. 


51 6  PHYSIOLOGICAL   CHEMISTRY 

end  of  15  minutes  aspirate  for  about  one -half  minute  to  remove  any  ammonia 
present  in  the  free  condition  in  "A."  After  this  aspiration,  open  "A"  and 
introduce  5  c.c.  of  saturated  potassium  carbonate.  Close  "A"  at  once  and 
aspirate  until  all  the  ammonia  has  been  removed  from  "A"  and  carried  over 
into  the  acid  in  "B."  The  time  needed  for  the  aspiration  varies  for  different 
pumps  from  5  to  30  minutes,  and  should  be  determined  by  trial  for  the  par- 
ticular apparatus  used.  At  the  end  of  the  time  needed  for  the  aeration,1  the 
pump  is  dIBonnected  (care  being  taken  to  avoid  back  suction)  and  the  ex- 
cess acid  in  "B"  is  titrated  by  means  of  fiftieth-normal  alkali. 

Calculations. — The  number  of  cubic  centimeters  of  fiftieth-normal  acid 
neutralized  is  multiplied  by  the  factor  0.056  to  give  the  number  of  grams 
of  urea-plus  ammonia-nitrogen  hi  100  c.c.  of  the  urine.  The  ammonia 
alone  may  be  determined  at  the  same  time  as  the  ammonia  plus  urea,  using 
the  same  technic  except  that  5  c.c.  of  the  undiluted  urine,  no  urease,  and  the 
factor  0.0056  are  used  for  the  determination  of  ammonia  alone.  The  am- 
monia tubes  are  run  hi  the  same  series  as  those  for  the  urea  determination, 
using  the  same  air  current  for  all. 

Interpretation. — The  mean  average  daily  excretion  of  urea  by  normal 
adults  is  usually  placed  at  about  30-35  grams  but  is  very  closely  de- 
pendent upon  the  protein  ingestion  and  hence  may  vary  widely.  It 
is  of  significance  only  when  the  amount  of  nitrogen  ingested  is  known 
with  some  degree  of  accuracy.  In  disorders  associated  with  increased 
tissue  catabolism  as  in  fevers,  the  excretion  of  urea  is  increased.  It 
may  be  decreased  in  pronounced  kidney  and  liver  disorders  due  to 
decreased  formation  and  decreased  power  of  elimination,  but  these 
findings  are  not  constant. 

The  per  cent  of  the  total  nitrogen  of  the  urine  occurring  as  urea 
varies  on  the  average  from  80-90.  On  a  high  protein  diet  it  is  nearer 
90  per  cent;  on  a  very  low  nitrogen  but  high  calorie  diet  it  may  not 
be  over  60  per  cent.  In  marked  acidosis  it  may  be  considerably 
decreased  relative  to  the  total  nitrogen  (see  ammonia). 

(b)  Youngburg's  Modification  of  Van  Slyke  and  Cullen's  Method.2 
— Principle. — The  ammonia  of  the  urine  to  be  analyzed  is  removed  by 
use  of  permutit,  and  urea  is  determined  in  the  ammonia  free  filtrate 
by  the  Van  Slyke  and  Cullen  procedure  using  the  alcoholic  urease 
solution  of  Folin  and  Youngburg  in  place  of  the  acetone  insoluble 
urease. 

Procedure. — Dilute  5  c.c.  of  urine  to  50  c.c.  (10  to  50  if  very  dilute  urine) 
and  mix  well.  Place  3  to  4  grams  of  dry  permutit  in  a  wide  bottomed  flask, 
preferable  a  200  c.c.  or  250  c.c.  volumetric,  and  add  20  to  25  c.c.  of  the  diluted 
urine.  Agitate  for  5  minutes.  Allow  to  settle  15  to  30  seconds  and  pour  through 

1  See  Fiske  (Jour.  Biol.  Chem.,  23,  455,  1915)  and  Van  Slyke  and  Cullen  (Jour.  Bid. 
Chem.,  24,  117,  1916)  for  discussion  of  details  of  method. 
2Youngburg,  G.  E.:  Jour.  Biol.  Chem.,  45,  391,  1921. 


URINE  517. 

a  thin  filter  paper  which  must  not  contain  any  appreciable  amount  of  ammonia. 
If  there  is  no  permutit  "  dust "  the  urine  may  be  decanted  without  filtering.  To 
5  c.c.  of  the  ammonia  free  filtrate  add  2  c.c.  of  alcoholic  urease  solution1  and  2 
drops  of  buffer  solution.2  Allow  15  minutes  for  decomposition  of  urea  by  the 
urease  solution  and  proceed  as  in  the  Van  Slyke  and  Cullen  method. 

Calculation.— The  number  of  cubic  centimeters  of  fiftieth-normal 
acid  neutralized  by  ammonia  during  aspiration  multiplied  by  the 
factor  0.056  gives  the  number  of  grams  of  urea  nitrogen  in  100  c.c.  of 
the  original  urine.  In  case  the  original  dilution  was  10  to  50  this  value 
must  be  divided  by  2. 

Interpretation. — See  page  516. 

(c)  Colorimetric  Modification  of  Van  Slyke  and  Cullen's  Method. — Rose  and 
Coleman3  suggest  the  colorimetric  determination  of  the  ammonia  which  is  carried 
over  by  the  aspiration,  rather  than  titration  of  the  excess  of  acid.  They  Nesslerize 
the  solution  in  "B,"  and  compare  the  color  produced  with  the  color  of  a  Nesslerized 
solution  of  known  ammonia  content,  as  in  the  Folin-Farmer  method  for  total 
nitrogen.  If  this  procedure  is  followed,  the  amount  of  urea  and  ammonia  nitrogen 
in  the  solution  acted  upon  by  the  urease  must  not  exceed  2  mg.  This  procedure 
has  been  found  useful  where  small  quantities  of  urea  are  to  be  estimated. 

(d)  Direct  Nesslerization  Method  of  Folin  and  Youngburg.4— 

Principle.— The  ammonia  is  removed  from  urine  by  permutit  and 
direct  Nesslerization  carried  out  on  the  ammonia — free  filtrate  follow- 
ing the  decomposition  of  the  urea  by  use  of  the  permutit  treated  urease 
solution. 

Procedure. — Place  i  c.c.  of  the  ammonia — free  urine  filtrate  (prepared  as 
described  in  the  preceding  method)  in  a  test  tube,  add  i  c.c.  of  the  alcoholic 
urease  solution,  and  i  drop  of  buffer  solution.  Digest  in  a  beaker  of  warm 
water  (4O-55°C.)  for  5  minutes  or  at  room  temperature  for  15  minutes,  at  the 
end  of  which  tune  transfer  the  contents  of  the  test  tube  to  a  200  c.c.  volumetric 
flask,  diluting  to  a  volume  of  about  150  c.c.  Prepare  a  standard  in  another 
200  c.c.  flask  by  adding  i  mg.  of  N  in  the  form  of  ammonium  sulphate,  i  c.c. 
of  urease  solution,  and  enough  ammonia  free  water  to  make  about  150  c.c. 
Then  add  20  c.c.  of  Nessler  solution5  to  each  flask,  dilute  to  volume  and  compare 
the  two  solutions  in  a  colorimeter. 

1  To  prepare  the  alcoholic  urease  solution  place  3  grams  of  permutit  in  a  flask,  wash 
once  with  2  per  cent  acetic  acid,  then  twice  with  water;  and  5  grams  of  fine  jack  bean  meal 
and  100  c.c.  of  30  per  cent  alcohol.     Shake  gently  but  continuously  for  10  to  15  minutes 
and  filter.     The  filtrate  contains  practically  all  of  the  urease  and  extremely  little  of  other 
materials. 

2  Dissolve  and  make  up  to  1000  c.c.  142  ,gms.  Na2HPO4  and  120  gms.  NaH2PO4  or 
equivalent  amounts  of  the  crystalline  salts. 

3  Rose  and  Coleman:  Biochem.  Bull.,  3,  411,  1914. 

4  Folin  and  Youngburg:  Jour.  Biol.  Chem.,  38,  in,  1919;  and  Youngburg:  ibid.,  45, 
319,  1921. 

6  The  Nessler  solution  is  prepared  according  to  the  procedure  of  Folin  and  Wu :  Jour. 
Biol.  Chem.,  38,  89,  1919,  in  the  following  manner. 

Mercuric  Potassium  Iodide  Preparation. — Transfer  150  gm.  of  potassium  iodide  and 
no  gm.  iodine  to  a  500  c.c.  Florence  flask;  add  100  c.c.  of  water  and  an  excess  of  metallic 
mercury,  140  to  150  gm.  Shake  the  flask  continuously  and  vigorously  for  7  to  15  minutes 
or  until  the  dissolved  iodine  has  nearly  disappeared.  The  solution  becomes  quite  hot. 


518  PHYSIOLOGICAL  CHEMISTRY 

Calculation. — The  standard  reading  divided  by  the  reading  of  the 
unknown  gives  the  number  of  milligrams  of  urea  N  in  0.5  c.c.  of  un- 
diluted urine. 

Interpretation. — See  page  516. 

(e)  Marshall's  Urease  Method.1 — Principle. — This  is  a  simple  clin- 
ical method  for  the  determination  of  urea  in  urine.     It  differs  from  the 
preceding  method  in  that  instead  of  aspirating  off  the  ammonia  formed 
from  the  urea  by  the  action  of  the  urease,  it  is  titrated  directly  in  the 
urine  mixture,  thus  simplifying  the  procedure.     The  method  is  nearly 
as  accurate  as  the  preceding,  for  normal  urine  the  error  being  only 
about  2  per  cent  which  is  very  satisfactory  for  a  rapid  clinical  procedure. 
For  diabetic  urines  the  aeration  procedure  should  be  used  as  such  urines 
contain  substances  which  render  the  titration  inaccurate. 

Procedure. — Two  5  c.c.  portions  of  the  urine  are  measured  into  flasks  of 
200-300  c.c.  capacity  and  diluted  with  distilled  water  to  about  100-125  c.c. 
One  c.c.  of  a  10  per  cent  solution  of  urease2  prepared  as  described  on  page  520  is 
added  to  one  flask,  a  few  drops  of  toluene  to  each  and  the  solution  allowed  to 
remain,  well  stoppered,  at  room  temperature  over  night  (or  five  hours).  The 
fluid  in  each  flask  is  titrated  to  a  distinct  pink  color  with  N/io  hydrochloric  acid 
using  methyl  orange  as  an  indicator.  A  few  cubic  centimeters  of  the  enzyme 
solution  used  should  also  be  titrated  to  determine  the  amount  of  N/io  hydro- 
chloric acid  required  to  neutralize  i  c.c. 

Calculation. — The  amount  of  hydrochloric  acid  required  for  the  contents  of 
the  flask  containing  the  urine  and  enzyme  solution,  less  the  amount  used  for 
5  c.c.  of  urine  alone  and  that  previously  determined  for  i  c.c.  of  enzyme  solution, 
corresponds  to  the  urea  originally  present  in  the  sample  of  urine.  Since  i  c.c. 
of  N/io  HC1  is  equivalent  to  3  mg.  of  urea,  the  number  of  cubic  centimeters 
required,  multiplied  by  0.6  gives  the  value  of  urea  expressed  in  grams  per  liter 
of  urine. 

Interpretation. — Seepage  516. 

(f)  Stehle's  Gasometric  Method  for  Urea.3— Shake  25  c.c.  of  diluted  urine 
(diluted  i  :  10)  with  4  grams  of  permutit  for  4  minutes.     Filter.     Introduce  i  c.c. 
of  the  nitrate  into  the  Van  Slyke  CO2  apparatus,  (see  p.  312),  rinsing  with  i  c.c.  of 

When  the  red  iodine  solution  has  begun  to  become  visibly  pale,  though  still  red,  cool  in 
running  water  and  continue  the  shaking  until  the  reddish  color  of  the  iodine  has  been  re- 
placed by  the  greenish  color  of  the  double  iodide.  The  whole  operation  usually  does  not 
take  more  than  15  minutes.  Now  separate  the  solution  from  the  surplus  mercury  by 
decantation  and  washing  with  liberal  quantities  of  distilled  water.  Dilute  the  solution 
and  washings  to  a  volume  of  2  liters.  If  the  solution  is  not  clear  allow  it  to  stand  for  i  or  2 
days  before  diluting  with  alkali  to  make  the  finished  Nessler  solution. 

Preparation  of  final  Nessler  Solution. — From  completely  saturated  caustic  soda  solu- 
tion containing  about  55  gm.  of  NaOH  per  100  c.c.  decant  the  clear  supernantant  liquid 
and  dilute  to  a  concentration  of  10  per  cent.  (It  is  well  to  determine  by  titration  that  the 
error  in  this  fo  per  cent  solution  is  not  over  5  per  cent).  Introduce  into  a  large  bottle 
3500  c.c.  of  10  per  cent  sodium  hydroxide  solution,  and  add  750  c.c.  of  the  stock  double 
iodide  solution  and  750  c.c.  of  distilled  water,  giving  5  liters  of  Nessler's  solution. 

1  Marshall:  Jour.  Biol,  Chem.,  14,  283,  1913. 

*  In  this  particular  method  urease  free  from  phosphate  should  be  used  as  the  presence 
of  these  salts  interferes  with  the  production  of  a  satisfactory  end-point. 

3  Private  communication  from  the  author. 


URINE  519 

water.  Extract  and  expel  the  air  from  urine  and  water.  Then  introduce  i  c.c.  of 
sodium  hypobromite1  solution.  The  mercury  is  lowered  to  the  50  c.c.  mark  and 
apparatus  is  then  shaken  vigorously  for  about  half  a  minute.  The  aqueous  solution 
is  collected  in  the  proper  chamber  below  the  lower  stopcock,  mercury  is  admitted  to 
the  50  c.c.  chamber,  and  after  adjusting  the  pressure,  the  volume  of  nitrogen  is  read. 
This  is  reduced  to  standard  conditions,  and  correction  is  made  for  air  in  the  hypo- 
bromite solution.  Between  15°  and  2o°C.  the  correction  is  0.006  c.c.,  and  between 
21°  and  25°C.,  it  is  0.005  c-c-  The  corrected  volume  is  then  transformed  into 
grams  of  nitrogen,  using  gas  reduction  tables  in  Chapter  IV. 

Ammonia 

.  I.  Folin's  Method. — Principle. — The  ammonia  of  the  urine  is  set 
free  by  the  addition  of  an  alkali  and  this  ammonia  is  then  carried  over 
by  an  air  current  into  a  flask  containing  a  measured  amount  of  standard 
acid.  The  excess  acid  is  then  titrated.  The  necessity  for  distillation 
is  avoided. 

Procedure. — Place  25  c.c.  of  urine  in  an  aerometer  cylinder,  30-40  cm.  in 
height  (Fig.  167,  below),  add  about  i  gram  of  dry  sodium  carbonate  and  introduce 
some  crude  petroleum  to  prevent  foaming.  Insert  into  the  neck  of  the  cylinder  a 
rubber  stopper  provided  with  two  perforations,  into  each  of  which  passes  a  glass 
tube,  one  of  which  reaches  below  the  surface  of  the  liquid.  The  shorter  tube 
(10  cm.  in  length)  is  connected  with  a  calcium  chloride  tube  filled  with  cotton,  and 
this  tube  is  in  turn  joined  to  a  glass  tube  extending  to  the  bottom  of  a  500  c.c. 


FIG.  167. — FOLIN  AMMONIA  APPARATUS. 

wide-mouthed  flask  which  is  intended  to  absorb  the  ammonia  and  for  this  pur- 
pose should  contain  20  c.c.  of  N/io  sulphuric  acid,  200  c.c.  of  ammonia-free 
distilled  water  and  a  few  drops  of  an  indicator  (alizarin  red  or  Congo  red).  To 
insure  the  complete  absorption  of  the  ammonia  the  absorption  flask  is  provided 
with  a  Folin  improved  absorption  tube  (Fig.  168),  which  is  very  effective  in 

xMade  by  mixing  equal  volume  of  two  solutions,  one  containing  12.5  gm.  sodium 
bromide  and  12.5  gm.  bromine  per  100  c.c.,  and  the  other  28  gm.  of  NaOH  per  100  c.c. 


520 


PHYSIOLOGICAL   CHEMISTRY 


causing  the  air  passing  from  the  cylinder  to  come  into  ultimate  contact  with 
the  acid  in  the  absorption  flask.  In  order  to  exclude  any  error  due  to  the 
presence  of  ammonia  in  the  air  a  similar  absorption  apparatus  to  the  one  just 
described  is  attached  to  the  other  side  of  the  aerometer  cylinder,  thus  insur- 
ing the  passage  of  ammonia-free  air  into  the  cylinder.  With  an  ordinary  filter 
pump  and  good  water  pressure  the  last  trace  of  ammonia  should  be  removed 
from  the  cylinder  in  about  one  and  one-half  hours.1  The  number  of  cubic 
centimeters  of  the  N/io  sulphuric  acid  neutralized  by  the  ammonia  of  the 
urine  may  be  determined  by  direct  titration  with  N/io  sodium  hydroxide. 

Steele2  has  suggested  a  modification  for  use  on  urines  containing 
triple  phosphate  sediments.  In  this  modification  0.5-1  .o  gram  of  NaOH 
and  about  15  grams  of  NaCl  are  substituted  for  the  Na2COs  of  the  Folin 
method.  The  use  of  sodium  hydroxide  and  chloride  instead  of  carbo- 
nate has  also  been  recommended  by  other  workers3  as  a  general  pro- 
cedure, inasmuch  as  triple  phosphate  crystals  are  almost  always  formed 
on  adding  sodium  carbonate  and  these  are  decomposed  with  some 
difficulty  by  sodium  carbonate  but  readily  by  the  hydroxide.  It 
has  not  been  shown  that  the  use  of  sodium  hydroxide  in  this  manner 

brings  about  the  decomposition  of  any  other  urinary 

nitrogen  compounds. 

Calculation. — Subtract  the  number  of  cubic  centimeters 
of  N/io  sodium  hydroxide  used  in  the  titration  from  the 
number  of  cubic  centimeters  of  N/io  sulphuric  acid  taken. 
The  remainder  is  the  number  of  cubic  centimeters  of  N/io 
sulphuric  acid  neutralized  by  the  NH3  of  the  urine.  One 
c.c.  of  N/io  sulphuric  acid  is  equivalent  to  0.0017  gram  of 
NH3.  Therefore  if  y  represents  the  volume  of  urine  used 
in  the  determination  and  y'  the  number  of  cubic  centi- 
meters of  N/io  sulphuric  acid  neutralized  by  the  NH3  of 
the  urine,  we  have  the  following  proportion : 

y':ioo::y'  X  0.0017  :x  (percentage  of  NH3  in  the  urine 
examined). 

Calculate  the  quantity  of  NH3  in  the  24-hour  urine 
specimen. 

Interpretation. — The  average  daily  output  of 
ammonia  in  the  urine  is  about  0.7  gram,  amounting 
to  2.5-4.5  per  cent  of  the  total  nitrogen  excretion. 
It  is  increased  by  the  ingestion  of  acids  or  acid-forming  foods  and 
decreased  by  the  ingestion  of  alkalis  or  base-forming  foods.  In  acid- 

1  With  any  given  filter  pump  a  "check"  test  should  be  made  with  urine  or,  better,  with  a 
solution  of  an  ammonium  salt  of  known  strength  to  determine  how  long  the  air  current  must 
be  maintained  to  remove  all  the  ammonia  from  25  c.c.  of  the  solution. 

2  Steele:  Jour.  Biol.  Chem.,  8,  365,  1910. 

3  Benedict  and  Osterberg:  Biochem.  Bull.,  3,  41,  1913. 
Shulansky  and  Gies:  Biochem.  Bull.,  3,  45,  1913. 


FIG.  1 6 8. —FOLIN 
IMPROVED  ABSORP- 
TION TUBE, 


URINE  521 

osis  it  may  be  very  greatly  increased,  being  excreted  in  combina- 
tion with  hydroxy butyric  and  other  acids.  Values  of  5  grams 
have  been  noted.  It  is  at  the  same  time  increased  relative  to  total 
nitrogen  and  urea.  In  pronounced  liver  disorders  the  same  thing  is 
noted,  as  ammonia  is  not  so  completely  transformed  into  urea  before 
excretion. 

2.  Micro-chemical  Method  of  FolinandMacCallum.1 — Principle. — 
This  method  is  a  combination  of  the  aeration  procedure  for  ammonia 
with  its  colorimetric  determination  by  means  of  Nessler-Winkler  solu- 
tion.    It  gives  satisfactory  results,  but  is  probably  not  as  accurate  as 
the  regular  Folin  procedure  where  the  amount  of  substance  for  analysis 
is  not  limited. 

Procedure. — By  means  of  Ostwald  pipettes  introduce  1-5  c.c.  of  urine2 
into  a  Jena  test-tube  (20-25  nun,  by  200  mm.)  and  add  to  the  urine  a  few  drops  of 
a  solution  containing  10  per  cent  of  potassium  carbonate  and  15  per  cent  of 
potassium  oxalate.  To  prevent  foaming  add  a  few  drops  of  kerosene  or  heavy, 
crude  machine  oil.  Pass  a  strong  air  current  (see  page  519)  through  the  mixture 
until  the  ammonia  has  been  entirely  removed.3  Collect  the  ammonia  in  a  100 
c.c.  volumetric  flask  containing  about  20  c.c.  of  ammonia-free  water  and  2  c.c. 
of  N/io  acid. 

Nesslerize  as  described  in  the  method  for  total  nitrogen,  page  510,  and  com- 
pare with  i  mg.  of  nitrogen  obtained  from  a  standard  ammonium  sulphate  solu- 
tion and  similarly  Nesslerized. 

It  has  been  noted  that  a  trace  of  something  capable  of  giving  a  color  with 
the  Nessler-Winkler  solution  continues  to  come  long  after  all  the  ammonia 
has  been  removed  from  the  urine.  The  nature  of  this  substance  has  not  yet 
been  determined.  In  actual  determinations  by  this  method,  the  influence  of 
this  unknown  substance,  because  of  the  small  volume  of  urine  used,  is  entirely 
negligible. 

3.  Formol  Titration  Method  (Malfatti).4— Principle.— This  method 
is    based    on    the   reaction    taking   place    when    formalin  solution  is 
added    to   a   solution   containing   ammonium   salts    (see   Amino-acid 
Nitrogen,    below).     An    acid    reaction   is    produced  in   the  mixture, 
which  is  then  titrated  with  standard  alkali  using  phenolphthalein  as 
an  indicator.     Amino-acids  give  the  same  reaction  so  that  the.  result 
of    the   titration   represents   ammonia  +  amino-acid   nitrogen.     This 
method  may  be  used  for  the  rapid  clinical  estimation  of  these  forms  of 
nitrogen  as  a  substitute  for  an  ammonia  determination,  but  the  results 
do  not  represent  ammonia  as  is  sometimes  stated. 

1  Folin  and  MacCallum:  Jour.  Biol,  Chem.,  n,  523,  1912. 

*  The  volume  of  urine  taken  should  contain  0.75-1.5  mg.  of  ammonia  nitrogen.  With 
normal  urines  2  c.c.  will  generally  yield  the  desired  amount.  With  very  dilute  urines  5 
c.c.  may  be  required,  while  with  diabetic  urines  rich  in  ammonium  salts  i  c.c.  may  be  exces- 
sive, thus  requiring  dilution. 

1  Ordinarily  a  period  of  ten  minutes  is  sufficiently  long 

4  Malfatti:  Z.  anal.  Chem.,  47,  273,  1908. 


522  PHYSIOLOGICAL  CHEMISTRY 

Procedure. — To  25  c.c.  of  urine  in  a  200  c.c.  Erlenmeyer  flask  add  15-20 
grams  of  finely  pulverized  potassium  oxalate,  a  few  drops  of  phenolphthalein, 
and  titrate  to  a  faint  but  permanent  pink  color  with  N/io  NaOH.  (The  urine 
mixture  just  after  neutralization  in  the  urinary  acidity  determination  (see  page 
499)  may  be  used.)  Then  add  10  c.c.  of  neutral  formalin  solution  (see  amino- 
acid  nitrogen),  mix  well  and  titrate  with  N/io  sodium  hydroxide  to  a  permanent 
pink  color. 

Calculation. — One  c.c.  of  N/io  sodium  hydroxide  is  equivalent  to  1.7 
mg.  of  ammonia.  Multiply  the  number  of  cubic  centimeters  of  N/io  alkali 
used  by  1.7  and  by  4  to  get  the  number  of  milligrams  of  ammonia  +  amino- 
acid  nitrogen  (expressed  as  ammonia)  in  100  c.c.  of  the  urine  examined. 

4.  Permutit  Method.1 — Principle. — The  urine  is  shaken  with 
particles  of  an  "  exchange  silicate,"  which  remove  the  ammonia  from 
solution.  The  ammonia  is  set  free  from  the  silicate  by  treating  with 
alkali  solution.  This  is  then  Nesslerized  and  compared  with  a  standard 
ammonia  solution  treated  in  the  same  way. 

Procedure. — Introduce  about  2  gm.  of  permutit  powder  into  a  200  c.c.  volu- 
metric flask.  Add  about  5  c.c.  of  water  (no  more),  and  with  an  Ostwald  pipette 
introduce  i  or  2  c.c.  of  urine,  or  with  a  5  c.c.  pipette  introduce  5  c.c.  of  previously 
diluted  urine  (corresponding  to  i  or  2  c.c.  of  the  original  urine).  With  urines 
very  low  in  ammonia  it  may  be  necessary  to  use  more  urine  (5  c.c.),  but,  in  so 
far  as  it  is  practicable,  it  is  better  not  to  use  more  than  2  c.c.  and  to  employ 
weaker  standard  (0.5  mg.  of  ammonia  nitrogen)  for  the  color  comparison. 
Rinse  down  the  added  urine  by  means  of  a  little  water  (i  to  5  c.c.),  and  shake 
gently  but  continuously  for  5  minutes.  Rinse  the  powder  to  the  bottom  of  the 
flask  by  the  addition  of  water  (25  to  40  c.c.)  and  decant.  Add  water  once  more 
and  decant.  (In  the  case  of  urines  rich  in  bile  it  is  advisable  to  wash  once  or 
twice  more.)  Add  a  little  water  to  the  powder,  introduce  2  c.c.  of  10  per  cent 
sodium  hydroxide,  shake  for  a  few  moments  and  set  aside,  while  preparing  the 
standard  ammonium  sulphate  solution  as  follows : 

Transfer  10  c.c.  of  the  standard  ammonium  sulphate  solution  (see  p.  511) 
containing  i  mg.  of  nitrogen  to  another  200  c.c.  volumetric  flask  and  add  2  c.c. 
of  10  per  cent  sodium  hydroxide  (to  balance  the  alkali  added  to  the  permutit 
mixture  in  the  other  flask).  Dilute  to  about  150  c.c.  and  mix.  Transfer  20  c.c. 
of  Nessler's  solution  (see  p.  517)  to  a  measuring  cylinder.  Now  give  the  volu- 
metric flask  a  vigorous  whirl  so  as  to  set  the  solution  spinning  within  the  flask 
and  add  at  once  the  whole  of  the  Nessler  solution  in  the  cylinder.  With  another 
whirling  movement  complete  the  mixing  of  the  contents  of  the  flask.  If  the 
process  of  Nesslerization  has  been  successful  a  deep  red  but  crystal  clear  solu- 
tion is  obtained.  If  it  is  not  perfectly  clear  throw  it  away  and  prepare  a  fresh 
standard.  Then  dilute  the  contents  of  the  flask  containing  the  permutit  and  the 
urinary  ammonia  to  about  150  c.c.,  whirl  the  mixture  and  add  the  Nessler  reagent 
(20  c.c.)  exactly  as  in  the  case  of  the  standard  solution.  Dilute  the  contents 
of  both  flasks  to  volume  (200  c.c.)  and  compare  in  a  colorimeter  with  the  stand- 
ard set  at  20  mm. 

1  Folin  and  Bell:  Jour.  BioL  Chem.,  29,  329,  1917. 


URINE  523 

~  .    ,    .        20  (reading  of  standard)  .    __ . 

Calculation :  _  ,  ,  — r-  =  me.  of  ammonia  N  in  amount  of  urine 

R  (reading  of  unknown) 

used. 

Calculate  the  per  cent  of  ammonia  and  the  24  hour  output. 

Interpretation. — See  page  520. 

Amino-acid  Nitrogen 

i.  Henriques-Sorensen  Formol  Titration  Method.1— Principle. — 
A  solution  containing  ammo-acids  is  nearly  neutral  in  reaction.  If 
formaldehyde  be  added,  however,  the  following  reaction  takes  place 
with  the  formation  of  methylene  derivatives  which  are  more  strongly  acid 
in  reaction  due  to  the  destruction  of  the  basic  properties  of  the  ammo 
groups.  The  carboxyl  groups  may  then  be  titrated  using  phenol- 
phthalein  as  an  indicator. 

R.CH.NH2 

+  CH20  =  R—  CH— N:  CH2  +  H2O. 
COOH 

COOH 

The  acidity  as  shown  by  the  titration  is  a  measure  of  the  amount  of 
amino-acid  nitrogen  present.  Ammonia  likewise  reacts  with  formalde- 
hyde in  a  similar  manner  as  is  shown  in  the  following  equation: 

4NH4C1  +  6CH20  =  N4(CH2)e  +  6H20  +  4HC1. 

Hence  the  formol  titration  in  the  presence  of  ammonia  gives  results 
which  include  both  amino-acid  and '  ammonia  nitrogen.  Ammonia 
may  be  determined  and  a  correction  applied,  or  the  ammonia  may  be 
removed  by  means  of  phosphotungstic  acid.  Phosphates  also  inter- 
fere by  obscuring  the  end-point  and  are  removed  by  the  addition  of 
barium  salts. 

It  must  be  borne  in  mind  that  polypeptides  and  still  more  complex 
protein  derivatives  likewise  react  with  formol  to  a  certain  degree  so 
that  the  results  do  not  strictly  represent  "  amino-acid  nitrogen." 

The  method  is,  with  some  modifications  involving  the  preparation 
of  the  solution  to  be  titrated,  applicable  in  the  determination  of  amino- 
acids  in  any  medium,  e.g.,  urine,  protein  digests,  etc.  When  poorly 
dissociated  acids,  e.g.,  some  fatty  acids,  are  present,  these  will  in  part 
be  included  in  the  result  and  lead  to  values  which  are  too  high.  Certain 
of  the  amino-acids  when  present  in  large  amounts  will  give  erroneous 
results,  but  in  the  ordinary  urine  or  digest  these  errors  are  either 
negligible  or  compensate  each  other.  In  the  titration  of  colored  solu- 
tions the  control' solution  which  is  necessary  in  this  method  must  be 
colored  to  correspond  with  the  color  of  the  unknown  solution. 

1  Henriques  and  Sorensen:  Zeit.  physiol.  chem.,  64,  120,  1909 


524 


PHYSIOLOGICAL   CHEMISTRY 


Procedure. — The  determination  of  the  amino-acids  is  carried  out  as  follows : 
The  solution  to  be  analyzed,  if  carbonates,  phosphates  and  ammonia  are  absent, 
is  made  neutral  to  litmus  (paper)  and  the  solution  titrated  with  formalde- 
hyde as  below.1  In  case  carbonates,  phosphates  or  ammonia  are  present  a 
preliminary  treatment  is  necessary  which  will  vary  according  to  the  quantity 
of  ammonia  present. 

(a)  For  Small  Amounts  of  Ammonia. — Applicable  to  most  urines.    Fifty 
c.c.  of  the  material  under  examination  is  pipetted  into  a  100  c.c.  measuring 
flask  and  i  c.c.  phenolphthalein  solution2  and  2  grams  of  solid  barium  chloride 
are  added ;  the  whole  is  shaken,  to  saturate  the  solution  with  barium  chloride ; 
saturated  barium  hydroxide  solution  is  added  until  the  red  color  of  the  phenol- 
phthalein develops  and  then  an  excess  of  5  c.c.  is  added.    The  flask  is  filled 
to  the  graduation  mark  with  water,  shaken  and  permitted  to  stand  for  15  minutes, 
after  which  it  is  filtered  through  a  dry  filter.    Eighty  c.c.  of  the  clear  red  filtrate 
(which  corresponds  to  40  c.c.  of  the  liquid  under  examination)  are  placed  in 
a  100  c.c.  measuring  flask,  neutralized  to  litmus  and  diluted  to  100  c.c.  with 
freshly  boiled  water.    Equal  portions  of  this  solution,  40  c.c.  (equivalent  to 
16  c.c.  of  the  original  solution),  may  be  taken  for  analysis,  one  for  the  formol 
titration  and  the  other  for  the  determination  of  ammonia  nitrogen.3 

(b)  For  Large  Amounts  of  Ammonia. — After  the  treatment  with  phenol- 
phthalein, barium  chloride,  and  barium  hydroxide,  and  the  solution  has  been 
diluted  to  100  c.c.  as  in  (a)  above,  the  ammonia  is  distilled  off,  in  vacuo.4 

In  case  the  solution  is  deeply  colored,  as  in  protein  digests,  it  may  be  neces- 
sary to  decolorize5  before  the  titration  is  attempted. 

Final  Titration. — For  the  final  titration  a  volume  of  from  20-40  c.c.  which  con- 
tains approximately  0.025  gram  of  nitrogen  is  the  most  desirable.  A  control 
solution  is  run  composed  of  an  equal  volume  of  boiled  distilled  water  and  20  c.c. 
of  the  formaldehyde  mixture.6  This  control  solution  is  colored7  so  that  its 
tint  matches  that  of  the  solution  to  be  titrated. 

To  this  control  is  added  about  half  the  volume  of  N/s  alkali  which  will  be 
used  in  the  titration  of  the  solution  under  investigation  and  it  is  then  titrated 
with  N/s  acid  to  a  faint  red  (first  stage).8 

An  additional  drop  of  N/5  alkali  is  added,  which  imparts  a  distinct  red  to  the 
solution  (second  stage). 

The  solution  to  be  analyzed  is  now  titrated  to  the  color  produced  in  the 

1  As  a  standard  of  comparison  the  litmus  paper  used  for  neutralization  is  contrasted  with 
a  similar  piece  dipped  in  a  phosphate  solution  having  a  neutral  reaction  (M/is  KH2PO4  and 
M/is  NasHPOO. 

2  A  solution  of  0.5  gram  of  phenolphthalein  in  50  c.c.  of  alcohol  and  50  c.c.  of  water. 

3  The  determination  of  ammonia  may  be  dispensed  with  in  case  a  separate  determina- 
tion is  made. 

4  For  particulars  with  regard  to  the  distillation,  etc.,  see  Henriques  and  Sorensen:  Zeit. 
physiol.  Chem.,  64,  137,  IQOQ. 

5  For  methods  see  jessen-Hansen,  Abderhalden's  Arbeits  Methoden,  vol.  6,  p.  262,  1912. 

6  The  formaldehyde  solution  is  freshly  prepared  for  each  set  of  determinations  as  follows: 
to  50  c.c.  of  commercial  formaldehyde  (formol)  (30-40  per  cent)  add  i  c.c.  of  the  phenol- 
phthalein solution.    N/5  alkali  is  then  added  until  the  mixture  acquires  a  faint  red  color. 
The  volume  of  the  formaldehyde  used  will  vary  with  the  volume  of  the  solution  to  be  ana- 
lyzed; approximately  10  c.c.  of  the  formalin  solution  are  added  for  each  20  c.c.  of  the  un- 
known solution. 

7  Solution  of  Bismark  brown  is  very  satisfactory  for  urines.     Tropaeolin  O,  Tropaeolin 
00,  £-nitro-phenol,  methyl  orange  or  alizarin  sulphonate,  may  be  used. 

8  This  procedure  is  recommended  in  order  that  the  final  volume  of  the  control  and  the 
unknown  solutions  shall  be  approximately  the  same  when  the  process  is  complete. 


URINE  525 

second  stage  of  the  control.  The  formaldehyde  mixture  is  now  added ;  10  c.c. 
for  each  20  c.c.  of  the  solution,  and  the  mixture  again  titrated  to  the  second 
stage  with  N/5  alkali.1 

Two  drops  of  the  N/5  alkali  are  now  added  to  the  control  solution  which 
assumes  a  deep  red  color  (third  stage).  Fifth  normal  alkali  is  now  added  to 
the  solution  under  examination  until  it  assumes  a  color  corresponding  to  the 
third  stage  of  the  control.  This  completes  the  titration. 

Calculation. — The  calculations  are  similar  to  those  which  pertain  to  any 
acidimetry  procedure.  Each  cubic  centimeter  of  an  N/5  alkali  or  acid  solution 
is  equivalent  to  0.0028  gram  of  nitrogen.  An  example  will  illustrate  the  pro- 
cedure: 40  c.c.  of  solution  (16  c.c.  of  urine)  required  5.10  c.c.  N/5  NaOH;  con- 
trol, o.io  c.c.  N/5  NaOH;  total  required  for  amino-acids  5.00  c.c.  equivalent  to 
0.014  gram  of  nitrogen.  Ammonia  nitrogen  in  16  c.c.  of  urine  0.007  gram  N. 
Then  0.014—0.007  =  0.007  gram  ammo-acid  nitrogen  in  16  c.c.  of  urine. 

Interpretation. — The  excretion  of  total  amino-acid  nitrogen  by  a 
normal  adult  averages  between  0.4  to  i.o  gram  per  day  or  from  2  to  6 
per  cent  of  the  total  nitrogen.  Free  amines-acid  nitrogen  (see  Van 
Slyke  procedure) " is  considerably  less  than  this,  ordinarily  0.5  to  i.o 
per  cent  of  the  total  nitrogen.  The  amount  may  be  largely  increased 
in  disorders  associated  with  tissue  waste  as  typhoid,  in  pronounced 
atrophy  of  the  liver,  acidosis,  etc. 

2.  Benedict-Murlin  Modification.2 — Principle. — In  this  method  the  ammonia  is 
removed  by  means  of  phosphotungstic  acid,  and  excess  acid  as  well  as  carbonates 
and  phosphates  carried  down  with  barium. 

Procedure. — Measure  into  a  500  c.c.  Erlenmeyer  flask  200  c.c.  of  a  24-hour  urine 
which  has  been  diluted  to  2000  c.c.  (or  its  equivalent).  Add  an  equal  volume 
of  10  per  cent  phosphotungstic  acid  (Merck)3  in  2  per  cent  HC1.  Let  stand  at  least 
three  hours,  better  over  night.  Pour  off  250  c.c.  of  the  clear  fluid,  add  i  c.c.  of  a 
0.5  per  cent  solution  of  phenolphthalein  and  then  barium  hydroxide  in  substance 
until  the  whole  fluid  turns  decidedly  pink.  The  barium  hydroxide  should  be  added 
a  very  little  at  a  time.  Let  stand  one  hour.  Filter  off  two  100  c.c.  samples  ( =  50 
c.c.  urine).  Neutralize  these  samples  to  litmus  (using  good  quality  litmus  paper) 
with  N/5  HC1.  Add  at  once  10-20  c.c.  of  neutral  formalin4  and  titrate  cautiously 
to  a  deep  red  color,  i.e.,  until  the  drop  produces  no  additional  color  with  N/io 
NaOH.  Deduct  from  the  result  thus  obtained  the  amount  of  N/io  NaOH  neces- 
sary to  produce  the  same  depth  of  color  in  an  equal  quantity  of  water,  freed  from 
carbon  dioxide  by  boiling  and  cooling,  and  to  which  an  equal  volume  of  neutral 
formalin  has  been  added. 

Calculation. — One  c.c.  of  N/io  NaOH  is  equivalent  to  1.4  nag.  of  amino-acid 
nitrogen.  Multiply  the  number  of  cubic  centimeters  of  N/io  NaOH  used  (after 
deducting  for  control  as  indicated  above)  by  1.4  and  by  2  (as  the  equivalent  of  50 

1  This  is  best  accomplished  by  adding  alkali  until  the  color  is  -deeper  than  that  of  the 
control,  then  acid  again  until  lighter  and  finally  alkali  to  the  desired  color. 

2  Benedict  and  Murlin:  Jour.  Biol.  Chem.,  16,  385,  1913. 

3  Kahlbaum's  preparation  is  a  very  different  substance. 

4  To  50  c.c.  commercial  formalin  solution  (30-40  per  cent)  add  i  c.c.  of  phenolphthalein 
solution  and  then  N/5  NaOH  to  a  very  faint  pink  color.    The  solution  should  be  freshly 
prepared. 


526  PHYSIOLOGICAL   CHEMISTRY 

c.c.  of  urine  was  used)  to  obtain  the  number  of  milligrams  of  amino-acid  nitrogen 
in  100  c.c.  of  the  urine. 

Interpretation. — See  page  525. 

3.  Method  of  Frey-Gigon. — The  ammonia  is  removed  from  the  urine  by  aspir- 
ation after  treatment  with  barium  hydroxide  and  the  formol  titration  performed  in 
the  usual  manner  (see  Frey  and  Gigon:  Biochem.  Zeit.,  22,  309,  1909). 

The  amino-acid  nitrogen  may  also  be  approximately  determined  by  carrying 
out  the  titration  for  ammonia  +  amino-acid  nitrogen  as  given  under  Ammonia, 
page  521,  making  a  separate  determination  of  ammonia,  and  subtracting  the  latter 
result  from  the  former. 

4.  Van  Slyke's  Method  for  Total  Amino-Acid  Nitrogen.1— Take  25  c.c.  of 
urine2  and  mix  with  i  c.c.  of  concentrated  sulphuric  acid  and  heat  in  an  auto- 
clave at  180°  (oil  bath  temperature)  for  one  and  one-half  hours.    Transfer  to  a 
50  c.c.  flask  and  add  2  grams  powdered  calcium  hydroxide.    Shake  thoroughly, 
make  up  to  50  c.c.  and  filter  through  a  dry  folded  filter.    Transfer  20  c.c.  of  the 
filtrate  to  a  Jena  glass  evaporating  dish  and  concentrate  to  dryness  on  the  water - 
bath.    This  requires  about  half  an  hour.    The  residue  is  moistened  with  i  c.c. 
of  50  per  cent  acetic  acid  to  bring  the  calcium  hydroxide  and  carbonate  into 
solution,  and  is  then  washed  into  a  10  c.c.  flask  and  filled  up  to  the  mark.    One 
can  use  the  entire  solution  for  determination  of  the  amino-nitrogen  in  the  large 
amino-apparatus,  or  use  2  c.c.  portions  for  the  micro-apparatus.     (See  Van 
Slyke  Apparatus,  Figs.  34  and  35,  p.  87  in  Chapter  IV  on  Proteins.) 

The  length  of  time  which  the  nitrous  acid  solution  should  be  shaken  in  order 
to  drive  off  all  the  amino-nitrogen  depends  somewhat  on  the  temperature. 
When  the  latter  is  15-20°  the  time  should  be  five  to  four  minutes;  for  20-25°  it 
is  three  minutes,  for  25-30°,  two  and  a  half  to  two  minutes.  It  is  preferable 
that  the  solution  should  be  shaken  vigorously  with  a  motor  and  the  time  kept 
down  to  these  limits,  for  the  sake  not  only  of  rapidity  but  of  accuracy. 

Van  Slyke's  Method  for  Free  Amino-Acid  Nitrogen. — To  25  c.c.  of  urine2 
hi  a  50  c.c.  flask  add  urease  solution  and  allow  to  stand  for  one  and  one-half 
times  the  interval  which  has  been  found  necessary  to  effect  the  maximum  de- 
composition of  urea,  as  observed  by  titration  of  the  ammonia.  The  last  traces 
of  urea  are  decomposed.  At  the  end  of  the  digestion  period  10  c.c.  of  a  10  per 
cent  suspension  of  calcium  hydroxide  are  added,  the  mixture  shaken  and  made 
up  to  50  c.c.  Then  filter,  evaporate,  and  complete  the  determination  according 
to  the  method  outlined  under  total  amino-acid  nitrogen,  above. 

Creatinine 

Folin's  Colorimetric  Method.— Principle. — This  method  is  based 
upon  the  characteristic  property  possessed  by  creatinine,  of  yielding  a 
certain  definite  color-reaction  in  the  presence  of  picric  acid  in  alkaline 
solution.  The  picric  acid  is  reduced  to  picramic  acid. 

Procedure. — Place  10  c.c.  of  urine  in  a  500  c.c.  volumetric  flask,  add  15  c.c.  of 
a  saturated  solution  of  picric  acid  and  5  c.c.  of  a  10  per  cent  solution  of  sodium  hy- 
droxide, shake  thoroughly  and  allow  the  mixture  to  stand  for  five  minutes.  Dur- 

1  Van  Slyke:  Jour.  Biol.  Chem.,  16,  125,  1913. 

2  See  (Van  Slyke:  Proc.  Soc.  Exp.  Biol.  and  Med.,  13,  63,  1915)  for  treatment  of  urines 
containing  glucose  or  albumin. 


URINE  527 

ing  this  interval  pour  a  little  N/2  potassium  bichromate  solution1  into  each  of  the 
two  cylinders  of  the  colorimeter  (Duboscq's,  see  Fig.  160,  p.  508)  and  carefully 
adjust  the  depth  of  the  solution  in  one  of  the  cylinders  to  the  8  mm.  mark.  A  few 
preliminary  colorimetric  readings  may  now  be  made  with  the  solution  in  the 
other  cylinder,  in  order  to  insure  greater  accuracy  in  the  subsequent  examination 
of  the  solution  of  unknown  strength.  Obviously  the  two  solutions  of  potassium 
bichromate  are  identical  in  color  and  in  their  examination  no  two  readings  should 
differ  more  than  0.1-0.2  mm.  from  the  true  value  (8  mm.).  Four  or  more  read- 
ings should  be  made  in  each  case  and  an  average  taken  of  all  of  them  exclusive 
of  the  first  reading,  which  is  apt  to  be  less  accurate  than  the  succeeding  readings. 
In  time  as  one  becomes  proficient  in  the  technic  it  is  perfectly  safe  to  take  the 
average  of  the  first  two  readings. 

At  the  end  of  the  five-minute  interval  already  mentioned,  the  contents  of  the 
500  c.c.  flask  are  diluted  to  the  500  c.c.  mark,  the  bichromate  solution  is  thor- 
oughly rinsed  out  of  one  of  the  cylinders  and  replaced  with  the  solution  thus  pre- 
pared and  a  number  of  colorimetric  readings  are  immediately  made. 

Ordinarily  10  c.c.  of  urine  is  used  in  the  determination  by  this  method,  but  if 
the  content  of  creatinine  is  above  15  mg.  or  below  5  mg.  the  determination  should 
be  repeated  with  a  volume  of  urine  selected  according  to  the  content  of  creatinine. 
This  variation  in  the  volume  of  urine  according  to  the  content  of  creatinine  is  quite 
essential,  since  the  method  loses  in  accuracy  when  more  than  15  mg.  or  less  than 
5  mg.  of  creatinine  is  present  in  the  solution  of  unknown  strength. 

Calculation.— By  experiment  it  has  been  determined  that  10  mg.  of  pure  crea- 
tinine, when  brought  into  solution  and  diluted  to  500  c.c.  as  explained  hi  the  above 
method,  yields  a  mixture  8.1  mm.  of  which  possesses  the  same  colorimetric  value 
as  8  mm.  of  a  N/2  solution  of  potassium  bichromate.  Bearing  this  in  mind  the 
computation  is  readily  made  by  means  of  the  following  proportion  in  which  y 
represents  the  number  of  millimeters  of  the  solution  of  unknown  strength  equiva- 
lent to  the  8  mm.  of  the  potassium  bichromate  solution : 

y  :8.i : :  10  :x  (mg.  of  creatinine  hi  the  quantity  of  urine  used). 

This  proportion  may  be  used  for  the  calculation  no  matter  what  volume  of 
urine  (5,  10,  or  15  c.c.)  is  used  in  the  determination.  The  10  represents  10  mg. 
of  creatinine  which  gives  a  color  equal  to  8.1  mm.,  whether  dissolved  in  5,  10,  or 
15  c.c.  of  fluid. 

Calculate  the  quantity  of  creatinine  in  the  24-hour  urine  specimen. 

Interpretation. — The  daily  excretion  of  creatinine  by  an  adult  of 
medium  weight  averages  about  1.25  grams.  The  value  is  nearly  con- 
stant from  day  to  day  for  a  given  individual  being  influenced  by  the  diet 
hardly  at  all  unless  this  contains  much  preformed  creatinine  (as  in  case 
of  a  heavy  meat  diet) .  The  excretion  of  creatinine  is  to  a  certain  extent 
a  measure  of  muscular  efficiency  and  of  the  amount  of  active  muscle 
tissue  in  the  body.  Relative  to  body  weight  less  creatinine  is  excreted 
by  obese  persons. 

Creatinine  excretion  is  decreased  in  disorders  associated  with  mus- 

1  This  solution  contains  24.55  grams  of  potassium  bichromate  to  the  liter.  A  pure 
creatinine  standard  is  to  be  preferred,  see  p.  528. 


528  PHYSIOLOGICAL  CHEMISTRY 

cular  atrophy  and  muscular  weakness.     It  increases  with  increased 
tissue  catabolism  as  in  fever. 

By  the  "creatinine  coefficient"  is  meant  the  number  of  milligrams 
of  creatinine — nitrogen  excreted  daily  per  kilo  of  body  weight.  This 
varies  under  normal  conditions  from  7-11. 

Use  of  Pure  Creatinine  Standards.— Instead  of  using  as  a  standard  a  potassium 
dichromate  solution  as  above  indicated,  a  solution  of  pure  creatinine  is  to  be  recom- 
mended. By  using  this  certain  arbitrary  factors  are  eliminated  and  the  method 
becomes  of  more  general  applicability.  The  standard  need  not  be  set  at  a  definite 
mark  as  is  necessary  in  the  case  of  dichromate  and  temperature  and  time  have  less 
influence  on  the  accuracy  of  the'results.  A  stock  solution  of  pure  creatinine  (made 
according  to  Benedict's  directions;  see  Chapter  XXIII  in  Physiological  Constituents 
of  Urine)  is  made  by  dissolving  i  gram  of  the  substance  in  sufficient  N/io  HC1  to 
make  a  liter.  This  solution  contains  i  mg.  of  creatinine  per  cubic  centimeter.  In 
carrying  out  the  determination  treat  10  c.c.  of  the  stock  solution  in  the  same  way  and 
at  the  same  time  as  the  10  c.c.  sample  of  urine.  Compare  in  the  colorimeter.  The 
calculation  is  simple.  The  reading  of  the  standard  divided  by  the  reading  of  the 
urine  gives  directly  the  number  of  milligrams  of  creatinine  per  cubic  centimeter  of 
urine. 

Folin's  Microchemical  Modification.1— Principle. — The  principle  is  the  same 
as  that  of  the  original  colorimetric  method  (see  page  526).  This  procedure  is  to  be 
recommended  particularly  where  only  small  amounts  of  material  are  available, 

Procedure. — One  c.c.  of  the  standard  creatinine  (see  above)  solution  (i  mg.  per 
c.c.)  is  measured  into  a  100  c.c.  volumetric  flask  and  i  c.c.  of  urine  into  another; 
20  c.c.  of  saturated  picric  acid  solution  (measured  with  a  cylinder)  are  added  to 
each  and  then  1.5  c.c.  of  a  10  per  cent  solution  of  sodium  hydroxide.  At  the  end 
of  ten  minutes  the  flasks  are  filled  up  to  the  mark  with  tap  water  and  the  color 
of  the  unknown  is  determined.  The  reading  of  the  standard  divided  by  the 
reading  of  the  unknown  gives  directly  the  number  of  milligrams  of  creatinine  in 
the  amount  of  urine  taken  for  analysis. 

3.  Shaffer's  Modification  for  the  Determination  of  Creatinine  in  Very  Dilute 
Solutions.2 — The  regular  Folin  procedure  is  not  accurate  when  applied  to  urines 
containing  less  than  20  mg.  of  creatinine  per  100  c.c.  By  a  slight  modification  it 
becomes  applicable  to  creatinine  solutions  containing  as  little  as  i  mg.  or  less  per 
100  c.c. 

Procedure. — To  the  solution  under  examination  add  an  equal  volume  of  satu- 
rated picric  acid  solution  and  one-tenth  this  volume  of  10  per  cent  sodium  hydroxide 
solution.  After  standing  6-10  minutes  the  liquid  is  diluted  to  a  definite  volume 
depending  upon  the  intensity  of  the  color  developed.  With  very  dilute  solutions 
one  may  add  solid  picric  acid  equivalent  to  half  saturation  (0.6  per  cent)  and  when 
dissolved,  one-twentieth  the  volume  of  sodium  hydroxide.  Provided  the  creatinine 
solution  itself  has  not  sufficient  color  to  interfere,  the  results  by  this  method  appear 
to  be  as  accurate  as  the  original  procedure.  The  colorimetric  readings  and  calcu- 
lations are  made  in  the  same  way  as  in  the  preceding  methods. 

1  Folin:  Jour.  Biol.  Chem.,  17,  469,  1914. 
1  Shaffer:  Jour.  Biol.  Chem.,  18,  525,  1914. 


URINE  529 

Creatine 

Folin-Benedict  Method.1 — Principle. — Creatine  on  boiling  with 
acid  is  transformed  into  creatinine.  By  determining  the  content  of 
creatinine  before  and  after  the  acid  treatment  we  are  able  to  calculate 
the  amount  of  creatine  originally  present  in  the  urine.  The  Folin 
colorimetric  method  (page  526)  is  used  for  determining  the  creatinine 
in  both  cases.  The  method  is  not  applicable  to  diabetic  urines. 

Procedure. — Introduce  into  a  small  flask  or  beaker  10  c.c.  of  the  urine  to 
be  examined.  (If  10  c.c.  contains  more  than  12  or  less  than  7  mg.  of  total 
creatinine  use  a  correspondingly  smaller  or  larger  volume  of  urine.)  Add  from 
10-20  c.c.  of  normal  HC1,  and  a  pinch  or  two  of  powdered  or  granulated  lead. 
Boil  the  mixture  over  a  free  flame  as  slowly  or  as  rapidly  as  may  be  desired,  until 
very  nearly  down  to  dryness,  when  the  heating  should  be  continued  to  dryness 
either  on  the  water-bath  or  very  easily  by  simply  holding  the  vessel  in  the  hand 
and  heating  carefully  for  a  moment  or  two.  Let  the  residue  stand  on  the  water- 
bath  for  a  few  minutes  until  most  of  the  excess  of  hydrochloric  acid  gas  has  been 
expelled,  after  which  dissolve  it  in  about  10  c.c.  of  hot  water  and  rinse  the  solu- 
tion quantitatively  through  a  plug  of  cotton  or  glass  wool  (to  remove  all  metallic 
lead)  into  a  500  c.c.  volumetric  flask.  Add  20-25  c.c.  of  a  saturated  picric  acid 
solution  and  about  7-8  c.c.  of  a  10  per  cent  NaOH  solution,  which  contains  5 
per  cent  of  Rochelle  salt.2  At  the  end  of  five  minutes  fill  to  the  mark  with  water 
and  read  in  the  colorimeter  just  as  in  the  case  of  creatinine  (see  page  526). 

Calculation. — Calculate  the  creatinine  content  of  the  solution  in  the  same 
manner  as  given  under  Creatinine  (page  527) .  From  the  value  thus  obtained  sub- 
tract the  value  for  the  creatinine  content  of  the  urine  before  dehydration.  The 
difference  will  be  the  creatine  content  of  the  original  urine  hi  terms  of  creatinine. 

Interpretation. — Creatine  occurs  only  in  very  small  amounts  in  the 
urine  of  normal  adults,  but  is  found  in  larger  amounts  in  that  of  children 
(10  to  50  mg.  per  day).  Creatine  ingestion  in  adults  has  little  effect 
on  the  urinary  excretion.  In  fasting,  the  amount  is  markedly  increased 
(it  may  amount  to  100  mg.  or  more  per  day).  Creatine  also  appears 
in  the  urine  after  high  water  ingestion.  It  is  found  in  many  pathological 
conditions  associated  with  malnutrition  and  disintegration  of  muscular 
tissue,  in  fever,  etc.  Very  large  amounts  have  been  found  in  cases  of 
carcinoma  of  the  liver. 

2.  Folin-Benedict  and  Myers  Method.3— To  20  c.c.  of  urine  in  a  50  c.c.  volu- 
metric flask,  add  20  c.c.  of  normal  hydrochloric  acid  and  place  the  flask  in  an  auto- 
clave at  a  temperature  of  ii7-i2o°C.  for  one-half  hour.  Add  distilled  water  until 
the  volume  of  the  acid-urine  mixture  is  exactly  50  c.c.,  close  the  flask  by  means  of 
a  stopper,  and  shake  it  thoroughly.  Approximately  neutralize  25  c.c.  of  this  mix- 

1  Benedict:  Jour.  Biol.  Chem.,  18,  191,  1914. 

2  The  Rochelle  salt  should  be  present  to  prevent  any  formation  of  turbidity,  which 
otherwise  may  occur,  due  to  the  presence  of  traces  of  dissolved  lead. 

3  Benedict  and  Myers:  Am.  J.  Phys.,  18,  397,  1907. 

34 


530  PHYSIOLOGICAL   CHEMISTRY 

ture,  introduce  it  into  a  500  c.c.  volumetric  flask  and  determine  its  creatinine  con- 
tent according  to  Folin's  Colorimetric  Method  (see  page  526). 
For  calculation  and  interpretation  see  the  foregoing  method. 

3.  Method  of  Folin.1 — Water-bath  Procedure. — Heat  10  c.c.  of  urine  with  5  c.c. 
of  normal  hydrochloric  acid  on  the  boiling  water-bath  or  at  9O°C.  for  three  hours. 
The  creatine  is  transformed  into  creatinine.     Some  darkening  takes  place  but  this 
does  not  interfere  because  of  the  subsequent  dilution.     The  mixture  is  made  up  to 
50  c.c.,  25  c.c.  of  this  is  taken,  neutralized,  and  creatinine  plus  creatine  determined 
just  as  in  the  case  of  creatinine  alone.    The  creatine  is  obtained  by  difference. 
This  procedure  may  be  used  for  diabetic  urines  which  is  not  the  case  with  the  auto- 
clave procedure  nor  with  the  Benedict  modification.    It  is  perhaps  not  quite  so 
accurate  as  the  autoclave  procedure. 

4.  Microchemical  Modification  of  Folin.2 — By  greatly  diluting  the  urine  the 
time  required  for  the  conversion  of  creatine  to  creatinine  is  decreased,  and  picric 
acid  can  be  substituted  for  mineral  acid. 

Procedure. — Enough  urine  to  give  0.7-1.5  mg.  of  creatinine  is  measured  into 
a  weighed  Erlenmeyer  Jena  flask  (capacity  200  c.c.);  20  c.c.  of  saturated  picric  acid 
solution,  about  130  c.c.  of  water,  and  a  few  very  small  pebbles  to  promote  even 
boiling  are  added  and  the  mixture  is  gently  boiled,  preferably  over  a  micro-burner 
for  about  one  hour.  At  the  end  of  this  time  the  heat  is  increased  and  the  solution 
is  boiled  down  to  rather  less  than  20  c.c.  The  flask  is  transferred  to  the  scales 
and  enough  water  is  added  to  make  the  total  solution  equal  to  20-25  grams.  The 
solution  is  cooled  in  running  water,  1.5  c.c.  of  10  per  cent  sodium  hydroxide  are 
added,  and  the  total  creatinine  is  determined  as  in  the  preformed  creatinine  deter- 
mination using  i  mg.  of  creatinine  as  a  standard.  The  method  has  been  found  to 
give  good  results  in  the  presence  of  glucose  and  other  sugars. 

Morris3  has  suggested  that  in  the  case  of  diabetic  urines  the  total  creatinine 
be  determined  after  precipitation  of  the  creatine  and  creatinine  with  picric  acid. 
The  method  is  not  recommended  as  a  regular  procedure. 

V 

Uric  Acid 

i.  Microchemical  Colorimetric  Method. — Method  of  Folin  and 
Wu*  Principle. — The  principle  of  the  method  depends  upon  the  fact, 
first  noted  by  Folin  and  Macallum5  and  further  investigated  by  Folin 
and  Denis,6  and  Benedict  and  Hitchcock,7  that  uric  acid  gives,  with 
phosphotungstic  acid  and  alkali,  a  deep  blue  color  the  depth  of  which  is 
proportional  to  the  amount  of  uric  acid  present.  Since  certain  other 
substances  present  in  urine  produce  a  similar  blue  color  with  the  phos- 
photungstic acid,  it  is  necessary  to  separate  the  uric  acid  from  them. 
This  is  accomplished  by  precipitation  as  the  silver  salt.  The  silver 
urate  is  subsequently  dissolved  and  treated  with  the  uric  acid  reagent. 

1  Folin:  Zeitschr.  f.  physiol.  Chem.,  41,  222,  1904. 

2  Folin:  Jour.  Bid.  Chem.,  17,  469,  1914. 

3  Morris:  Jour.  Biol.  Chem.,  21,  201,  1915. 

4  Folin  and  Wu:  Jour.  Biol.  Chem.,  38,  459,  1919. 

6  Folin  and  Macallum:  Jour.  Biol.  Chem.,  13,  363,  1912. 

6  Folin  and  Denis:  Jour.  Biol.  Chem.,  14,  95,  1913;  ibid.,  13,  469,  1913. 

7  Benedict  and  Hitchcock:  /.  Biol.  Chem.,  20,  619,  1915;  Benedict:  ibid,t  20,  629, 1915. 


URINE  531 

Procedure. — Transfer  1-3  c.c.  of  urine,  according  to  concentration,  to  a 
centrifuge  tube  and  add  water  to  a  volume  of  about  6  c.c.  Add  5  c.c.  of  a  silver 
lactate  solution  (silver  lactate  5  per  cent.,  lactic  acid  5  per  cent)  and  stir  with  a 
fine  glass  rod.  Rinse  the  rod  with  a  few  drops  of  water.  Centrifuge  the 
counterbalanced  tube  for  2-3  minutes.  Add  a  drop  of  silver  lactate  solution 
so  as  to  be  sure  that  an  excess  is  present ;  if  a  precipitate  (of  AgCl)  is  formed, 
add  2  c.c.  more  of  the  silver  solution  and  centrifuge  again ;  if  no  precipitate 
forms  pour  off  the  liquid  as  completely  as  possible. 

To  the  precipitate  in  the  centrifuge  tube  add,  from  a  buret,  4  c.c.  of  a  5  per 
cent  sodium  cyanide  solution  (poisonous — 3  c.c.  may  be  fatal  dose).  Stir  the 
mixture  until  a  perfectly  clear  solution  is  formed.  Rinse  the  stirring  rod,  collect- 
ing the  rinsings  in  a  100  c.c.  volumetric  flask ;  pour  the  contents  of  the  tube  into 
the  same  flask  and  rinse  the  tube  3  times  with  about  5  c.c.  of  water.  Add  5 
c.c.  of  a  10  per  cent  sodium  sulphite  solution  (to  balance  the  sulphite  in  the 
standard  uric  acid  solution)  and  dilute  to  a  volume  of  about  40  c.c.  In  another 
100  c.c.  flask  place  5  c.c.  of  a  standard  uric  acid  sulphite  solution1  containing 
0.5  mg.  of  uric  acid ;  add  4  c.c.  of  cyanide  solution  and  about  35  c.c.  of  water. 
Then  add  20  c.c.  of  20  per  cent  sodium  carbonate  solution2  to  each  flask  and 
finally  add  with  shaking  2  c.c.  of  the  uric  acid  reagent.3  Let  stand  3-5  minutes, 
fill  to  the  mark,  mix  and  compare  the  two  colored  solutions  in  a  colorimeter. 

Calculation. — Since  the  standard  is  0.5  mg.,  if  the  standard  is  set  at  20  mm. 
divide  10  by  the  reading  of  the  unknown  (in  mm.)  to  obtain  the  amount  of  uric 
acid  (in  mg.)  in  the  amount  of  urine  taken. 

Interpretation. — For  adults  on  a  mixed  diet  the  average  excretion  of 
uric  acid  is  about  0.7  gram.  It  arises  from  the  purines  of  ingested  food 
(exogenous  uric  acid)  and  from  purines.  derived  from  the  body  tissues 
by  disintegration  of  nuclein  material  (endogenous  uric  acid).  Exoge- 
nous uric  acid  depending  entirely  upon  the  diet  is  greatly  increased 
by  the  ingestion  of  purine-rich  foods  (meat,  liver,  sweetbreads,  etc.)  and 
reduced  to  a  very  low  level  on  purine-free  foods,  e.g.,  milk,  eggs,  etc. 
(see  Chapter  XXVIII) .  Endogenous  uric  acid  is  influenced  by  exercise 
and  by  the  diet  (protein  foods  particularly  giving  rise  to  increases). 
It  appears  to  be  partly  the  result  of  gastro-intestinal  secretory  activity. 
On  a  purine-free  diet  the  average  excretion  is  0.1-0.5  gram.  On  a  high 
purine  diet  the  uric  acid  output  may  be  2  grams  per  day. 

1  Preparation  of  Standard  Uric  Acid  Solution. — In  a  500  c.c.  flask  dissolve  exactly  i  g 
of  uric  acid  in  150  c.c.  of  water  by  the  help  of  0.5  g.  lithium  carbonate.  Dilute  to  500  c.c. 
and  mix.  Transfer  50  c.c.  to  a  liter  flask,  add  500  c.c.  of  20  per  cent  sodium  sulphite 
solution,  dilute  to  volume  and  mix.  Each  c.c.  of  this  solution  is  then  "equal  to  o.i  mg.  of 
uric  acid.  Transfer  to  small  bottles  (cap.  200  c.c.)  and  stopper  tightly.  This  standard 
uric  acid  solution  keeps  almost  indefinitely  in  unopened  bottles,  because  the  sulphite  pre- 
vents the  spontaneous  oxidation  of  the  uric  acid.  In  used  bottles  the  standard  usually 
remains  good  for  2-3  months. 

2Sodium  Carbonate  Solution. — Dissolve  200  grams  of  anhydrous  sodium  carbonate  in 
warm  water,  cool  and  dilute  to  i  liter. 

Preparation  of  Uric  Acid  Reagent.— Introduce  into  a.flask  700  c.c.  of  water,  100  g. 
of  sodium  tungstate,  and  80  c.c.  of  phosphoric  acid  (85  per  cent  HsPO^.  Partly  close 
the  rnguth  of  the  flask  with  a  funnel  and  a  small  watch  glass  and  boil  gently  for  2  hours. 
Dilute  to  i  liter. 


532  PHYSIOLOGICAL   CHEMISTRY 

In  gout  the  uric  acid  content  of  the  urine  is  low  preceding  an  attack 
and  increases  during  the  attack,  this  fall  and  rise  being  more  or  less 
characteristic.  The  excretion  rises  after  atophan  administration  ap- 
parently due  to  increased  kidney  activity.  In  leukemia  the  excretion 
is  extremely  high  due  to  nuclear  destruction.  The  uric  acid  content 
of  the  urine  is  of  importance  in  relation  to  the  formation  of  uric  acid 
calculi.  The  administration  of  alkali  carbonates  and  citrates  by  de- 
creasing the  acidity  of  the  urine  increases  its  solvent  power  for  uric 
acid,  and  decreases  the  liability  of  the  formation  of  this  type  of  calculus. 

2.  Folin-Shaffer  Method.1 — Principle. — The  uric  acid  is  precipitated  as  am- 
monium urate  by  the  addition  of  ammonia,  the  precipitate  filtered  off,  washed 
and  titrated  with  potassium  permanganate.  A  preliminary  treatment  with  an 
ammonium  sulphate-uranium  acetate  solution  is  for  the  purpose  of  removing 
interfering  organic  substances.  The  method  gives  accurate  results. 

Procedure. — Introduce2  100  c.c.  of  urine  into  an  Erlenmeyer  flask,  add  25  c.c. 
of  the  Folin-Shaffer  reagent3  and  after  shaking  the  flask  to  thoroughly  mix  the 
fluids  allow  the  mixture  to  stand,4  with  or  without  further  stirring,  until  the 
precipitate  has  settled  (5-10  minutes).  Filter,  transfer  100  c.c.  of  the  filtrate  to  a 
200  c.c.  Erlenmeyer  flask,  add  5  c.c.  of  concentrated  ammonium  hydroxide  and  allow 
the  mixture  to  stand  for  24  hours.  Transfer  the  precipitated  ammonium  urate 
quantitatively  to  a  filter  paper,5  using  10  per  cent  ammonium  sulphate  to  remove 
the  final  traces  of  the  urate  from  the  flask.  Wash  the  precipitate  approximately 
free  from  chlorides  by  means  of  10  per  cent  ammonium  sulphate  solution,6  remove 
the  paper  from  the  funnel,  open  it,  and  by  means  of  hot  water  rinse  the  precipi- 
tate back  through  the  funnel  into  the  flask  in  which  the  urate  was  'originally 
precipitated.  The  volume  of  fluid  at  this  point  should  be  about  100  c.c.  Cool 
the  solution  to  room  temperature,  add  15  c.c.  of  concentrated  sulphuric  acid  and 
titrate  at  once  with  N/20  potassium  permanganate,  K2Mn2O8,  solution.  The 
first  tinge  of  pink  color  which  extends  throughout  the  fluid  after  the  addition  of 
two  drops  of  the  permanganate  solution,  while  stirring  with  a  glass  rod,  should 
be  taken  as  the  end-reaction.  Take  the  burette  reading  and  compute  the 
percentage  of  uric  acid  present  in  the  urine  under  examination. 

Calculation — Each  cubic  centimeter  of  N/20  potassium  permanganate  solution 
is  equivalent  to  3.75  mg.  (0.00375  gram)  of  uric  acid.  The  100  c.c.  from  which 
the  ammonium  urate  was  precipitated  is  equivalent  to  only  four-fifths  of  the  100 
c.c.  of  urine  originally  taken;  therefore  we  must  take  five-fourths  of  the  burette 
reading  in  order  to  ascertain  the  number  of  cubic  centimeters  of  the  perman- 
ganate solution  required  to  titrate  100  c.c.  of  the  original  urine  to  the  correct 

1  Folin  and  Shaffer:  Zeit.  physiol.  Chem.,  32,  552,  1901. 

2  It  is  preferable  to  use  more  than  100  c.c.  of  urine  if  the  fluid  has  a  specific  gravity  less 
than  i  020. 

3  The  Folin-Shaffer  reagent  consists  of  500  grams  of  ammonium  sulphate,  5  grams  of 
uraniu.m  acetate  and  60  c.c.  of  10  per  cent  acetic  acid  in  650  c.c.  of  distilled  water. 

4  The  mixture  should  not  be  allowed  to  stand  for  too  long  a  time  at  this  point,  since  uric 
acid  may  be  lost  through  precipitation. 

6  The  Schleicher  and  Schiill  hardened  papers  or  the  Baker  and  Adamson  washed,  askless 
variety  are  very  satisfactory  for  this  purpose. 

6  This  washing  may  be  conveniently  done  by  Recantation  if  desired,  thus  retaining  the 
major  portion  of  the  precipitate  in  the  flask. 


•URINE  533 

end  point.     If  y  represents  the  number  of  cubic  centimeters  of  the  permanganate 
solution  required,  we  may  make  the  following  calculation: 

y  X  0.00375  =  weight  of  uric  acid  in  100  c.c.  of  urine. 

Because  of  the  solubility  of  the  ammonium  urate  a  correction  of  3  mg.  should 
be  added  to  the  final,  result. 

Calculate  the  quantity  of  uric  acid  in  the  24-hour  urine  specimen. 

3.  Kruger-Schmidt  Method. — Kriiger  and  Schmidt  have  devised  a  method 
for  the  combined  determination  of  uric  acid  and  the  other  purine  bodies  of  urine. 
This  procedure  is  described  under  Purine  Bases,  below.  A  modification  of  this 
method  by  Hunter  is  also  given. 

Purine  Bases 

i.  Kriiger  and  Schmidt's  Method. — Principle. — This  method  serves 
for  the  determination  of  both  uric  acid  and  the  purine  bases.  The 
principle  involved  is  the  precipitation  of  both  the  uric  acid  and  the 
purine  bases  in  combination  with  copper  oxide  and  the  subsequent 
decomposition  of  this  precipitate  by  means  of  sodium  sulphide.  The 
uric  acid  is  then  precipitated  by  means  of  hydrochloric  acid  and  the 
purine  bases  are  separated  from  the  filtrate  in  the  form  of  their  copper 
or  silver  compounds.  The  nitrogen  content  of  the  precipitates  of  uric 
acid  and  purine  bases  is  then  determined  by  means  of  the  Kjeldahl 
method  (see  page  504)  and  the  corresponding  values  for  uric  acid  and 
purine  bases  calculated. 

Procedure. — To  400  c.c.  of  albumin-free  'urine1  in  a  liter  flask,2  add  24 
grams  of  sodium  acetate,  40  c.c.  of  a  solution  of  sodium  bisulphite3  and  heat 
the  mixture  to  boiling.  Add  40-80  c.c.4  of  a  10  per  cent  solution  of  copper 
sulphate  and  maintain  the  temperature  of  the  mixture  at  the  boiling-point  for 
at  least  three  minutes.  Filter  off  the  flocculent  precipitate,  wash  it  with  hot 
water  until  the  wash  water  is  colorless,  and  return  the  washed  precipitate  to 
the  flask  by  puncturing  the  tip  of  the  filter  paper  and  washing  the  precipitate 
through  by  means  of  hot  water.  Add  water  until  the  volume  in  the  flask  is 
approximately  200  c.c.,  heat  the  mixture  to  boiling  and  decompose  the  precipi- 
tate of  copper  oxide  by  the  addition  of  30  c.c.  of  sodium  sulphide  solution.5 
After  decomposition  is  complete,  the  mixture  should  be  acidified  with  acetic 
acid  and  heated  to  boiling  until  the  separating  sulphur  collects  in.  a  mass.  Filter 

1  If  albumin  is  present,  the  urine  should  be  heated  to  boiling,  acidified  with  acetic  acid 
and  filtered. 

2  The  total  volume  of  urine  for  the  24  hours  should  be  sufficiently  diluted  with  water  lo 
make  the  total  volume  of  the  solution  1600-2000  c.c. 

3  A  solution  containing  50  grams  of  Kahlbaum's  commercial  sodium  bisulphite  in  ico 
c.c.  of  water. 

4  The  exact  amount  depending  upon  the  content  of  the  purine  bases. 

5  This  is  made  by  saturating  a  i  per  cent  solution  of  sodium  hydroxide  with  hydrogen 
sulphide  gas  and  adding  an  equal  volume  of  i  per  cent  sodium  hydroxide. 

Ordinarily  the  addition  of  30  c.c.  of  this  solution  is  sufficient,  but  the  presence  of  an 
excess  of  sulphide  should  be  proven  by  adding  a  drop  of  lead  acetate  to  a  drop  of  the  solution. 
Under  these  conditions  a  dark  brown  color  will  show  the  presence  of  an  excess  of  sodium 
sulphide. 


534  PHYSIOLOGICAL   CHEMISTRY 

the  hot  fluid  by  means  of  a  filter-pump,  wash  with  hot  water,  add  10  c.c.  of  10 
per  cent  hydrochloric  acid  and  evaporate  the  filtrate  in  a  porcelain  dish  until 
the  total  volume  has  been  reduced  to  about  10  c.c.  Permit  this  residue  to 
stand  about  two  hours  to  allow  for  the  separation  of  the  uric  acid,  leaving  the 
purine  bases  hi  solution.  Filter  off  the  precipitate  of  uric  acid,  using  a  small 
filter  paper,  and  wash  the  uric  acid,  with  water  made  acid  with  sulphuric  acid, 
until  the  total  volume  of  the  original  filtrate  and  the  wash  water  aggregates 
75  c.c.  Determine  the  nitrogen  content  of  the  precipitate  by  means  of  the  Kjel- 
dahl  method  (see  page  504),  and  calculate  the  uric  acid  equivalent.1 

Render  the  filtrate  from  the  uric  acid  crystals  alkaline  with  sodium  hydroxide, 
add  acetic  acid  until  faintly  acid  and  heat  to  7o°C.  Now  add  i  c.c.  of  a  10  per 
cent  solution  of  acetic  acid  and  10  c.c.  of  a  suspension  of  manganese  dioxide2 
to  oxidize  the  traces  of  uric  acid  which  remain  hi  the  solution.  Agitate  the  mix- 
ture for  one  minute,  add  10  c.c.  of  the  sodium  bisulphite  solution3  and  5  c.c. 
of  a  10  per  cent  solution  of  copper  sulphate  and  heat  the  mixture  to  boiling  for 
three  minutes.  Filter  off  the  precipitate,  wash  it  with  hot  water,  and  determine 
its  nitrogen  content  by  means  of  the  Kjeldahl  method  (see  page  504).  Inas- 
much as  the  composition  and  proportion  of  the  purine  bases  present  in  urine  is 
variable,  no  factor  can  be  applied.  The  result  as  regards  these  bases  must 
therefore  be  expressed  hi  terms  of  nitrogen. 

Benedict  and  Saiki4  report  cases  in  which  the  total  purine  nitrogen  by  this 
method  was  less  than  the  uric-acid  nitrogen  as  determined  by  the  Folin-Shaffer 
method.  The  inaccuracy  was  found  to  lie  in  the  Kriiger  and  Schmidt  method. 
To  obviate  this  they  advise  the  addition  of  20  c.c.  of  glacial  acetic  acid  for  each 
300  c.c.  of  urine  employed,  the  acid  being  added  before  the  first  precipitation. 

Interpretation. — The  amount  of  purine  bases  excreted  by  a  normal 
man  is  small  and  variable.  Values  from  16-60  mg.  have  been  found. 
The  purine  base  nitrogen  is  of  course  only  a  fraction  of  this.  The 
amount  excreted  is  influenced  by  the  diet  somewhat  in  the  same  way 
as  is  the  excretion  of  uric  acid  being  also  increased  in  disorders  asso- 
ciated with  increased  uric  acid  excretion  such  as  leukemia.  The  purine 
bases  form  a  higher  percentage  of  the  total  purine  excretion  in  the  case 
of  the  monkey,  sheep,  and  goat  than  in  the  case  of  man. 

2.  Hunter  and  Givens*  Modification  of  Kriiger-Schmidt  Method. 5 — 
Principle. — The  Kruger-Schmidt  process  is  combined  with  the  micro- 
chemical  colorimetric  method  for  uric  acid  (see  page  530). 

Procedure. — The  first  copper-purine  precipitate  as  obtained  in  the  Kruger- 
Schmidt  procedure  is  suspended  in  about  200  c.c.  of  water,  to  which  there  is 
added  about  i  c.c.  of  concentrated  hydrochloric  acid.  The  mixture  is  vigorously 
boiled,  whereupon  the  whole  or  greater  part  of  the  precipitate  goes  into  solution. 
Removal  of  the  copper  is  effected  by  treatment  with  hydrogen  sulphide  in  the 

1  This  may  be  done  by  multiplying  the  nitrogen  value  of  three  and  adding  3.5  mg. 
to  the  product  as  a  correction  for  the  uric  acid  remaining  in  solution  in  the  75  c.c. 

J  Made  by  heating  a  0.5  per  cent  solution  of  potassium  permanganate  with  a  little  alco- 
hol until  it  is  decolorized. 

1  To  dissolve  the  excess  of  manganese  dioxide. 

4  Benedict  and  Saiki:  Jour.  Biol.  Chem.,  7,  27,  1909. 

5  Hunter  and  Givens:  Jour.  Biol.  Chem.,  17,  37,  1914. 


URINE  535 

heat,  and  excess  of  the  sulphide  is  completely  expelled  by  renewed  boiling.  Fil- 
tration under  suction,  and  thorough  washing  of  flask  and  filter  result  in  a  filtrate 
which  is  perfectly  clear  and  nearly  colorless.  This  is  concentrated  if  necessary, 
and  made  up  to  a  convenient  volume  which  must  of  course  be  sufficiently  large  to 
retain,  when  cool,  the  uric  acid  hi  solution.  Of  this  an  aliquot  part  is  utilized 
directly  for  the  cqlorimetric  determination  of  uric  acid.  In  the  remainder  the 
residual  uric  acid  is  destroyed  and  bases  determined  according  to  the  regular 
Kriiger-Schmidt  procedure.  This  modification  is  recommended  particularly 
where  the  amount  of  uric  acid  present  is  minute. 

3.  Welker's  Modification  of  the  Methods  of  Arastein  and  of  Salkowski.2 — 
Principle. — The  phosphates  are  removed  by  treatment  with  magnesia  mixture. 
The  purine  bases  and  uric  acid  are  then  thrown  down  as  their  silver  salts  and  the 
nitrogen  content  of  this  precipitate  determined. 

Procedure. — Four  hundred  c.c.  of  urine,  free  from  protein,  are  treated  with 
100  c.c.  of  magnesia  mixture  and  600  c.c.  of  water.  This  is  then  filtered  and  of  the 
clear  nitrate  a  measured  quantity  (600-800  c.c.)  is  treated  with  an  excess  (10  c.c.) 
of  a  3  per  cent  silver  nitrate  solution.  Concentrated  ammonium  hydroxide  is 
added  in  small  quantities,  with  stirring,  until  all  the  chlorides  have  dissolved. 
Allow  the  flocculent  precipitate  of  the  silver  purine  compounds  to  settle  to  the  bot- 
tom, then  pass  the  supernatant  liquid  through  the  filter  before  disturbing  the 
precipitate.  Finally  transfer  the  precipitate  quantitatively  to  the  paper  which 
must  be  of  known  nitrogen  content.  The  precipitate  is  washed  with  dilute  (i  per 
cent)  ammonium  hydroxide.  The  paper  with  the  precipitate  is  then  transferred 
to  a  Kjeldahl  flask  and  about  TOO  c.c.  of  water  and  a  small  quantity  (about  o.i 
gram)  of  magnesium  oxide  are  added.  The  water  is  then  boiled  until  all  the  am- 
monia has  been  driven  off.  Test  the  steam  with  litmus  paper. 

The  material  in  the  flask  is  then  digested  by  means  of  the  usual  Kjeldahl  method 
(see  page  504).  The  digestion  must  be  watched  carefully  at  the  time  the  sulphuric 
acid  reaches  sufficient  concentration  to  affect  the  filter  paper,  inasmuch  as  the  SOj 
produced  causes  considerable  frothing.  The  total  nitrogen  (purine  base,  uric  acid 
and  filter-paper  nitrogen)  is  now  determined  in  the  usual  way  (see  Kjeldahl  Method, 
page  504).  This  result  minus  the  uric  acid  and  filter-paper  nitrogen  will  give  the 
figure  for  the  purine-base  nitrogen. 

Allantoin 

i.  Method  of  Wiechowski-Handovsky.2 — Principle. — The  urine  is  precipitated 
with  phosphotungstic  acid  and  lead  acetate  and  in  the  presence  of  chlorides  with 
silver  acetate.  The  heavy  metals  are  removed  with  hydrogen  sulphide.  The  allan- 
toin  is  then  precipitated  as  a  mecuric  compound  and  the  amount  of  mercury  and 
hence  of  allantoin  in  the  precipitate  determined  by  titration  with  ammonium 
thiocyanate.  This  method,  though  rather  tedious,  is  probably  the  most  accurate 
method  for  the  determination  of  allantoin. 

Procedure.—  The  urine  is  diluted  to  about  i  per  cent  urea.  As  rabbit  urine 
contains  in  the  day's  output  about  2-4  grams  of  urea,  and  that  of  other  herbivora 
usually  forms  about  a  4  per  cent  urea  solution,  it  is  usually  desirable  to  dilute  3-4 

1  Dittman  and  Welker:  New  York  Med.  Jour.,  May- June,  1909. 
s  Handovsky:  Zeit.  physiol.  Chem.,  go,  211,  1914. 
Wiechowski:  Neubauer-Huppert:  Analyse  des  Harns,  Wiesbaden,  1913,  p.  1076. 


536  PHYSIOLOGICAL  CHEMISTRY 

times.  A  greater  dilution  is  not  desirable.  The  urine  is  treated  with  i  per  cent  of 
sulphuric  acid  and  about  3  c.c.  of  acetic  acid  for  each  day's  volume.  Test  a  small 
quantity  of  the  urine  to  determine  the  amount  of  50  per  cent  phosphotungstic  acid 
required  to  completely  precipitate  it.  The  bulk  of  the  urine  is  then  treated  on  this 
basis  with  sufficient  solid  phosphotungstic  acid  to  precipitate  it  completely.  Stir 
to  dissolve  the  acid  and  allow  to  stand  for  several  hours.  Filter  with  suction,  first 
lining  the  filter  with  infusorial  earth  by  rubbing  up  a  little  of  the  substance  with  some 
of  the  urine  mixture  and  filtering  with  suction.  To  some  ordinary  lead  oxide  in  a 
mortar  add  a  small  amount  of  the  filtrate  and  stir  until  it  becomes  warm,  then  add 
the  rest  of  the  filtrate  and  stir,  adding  more  oxide  if  necessary  until  the  solution 
reacts  alkaline  due  to  the  formation  of  basic  lead  acetate. 

Filter  again.  The  filtrate  should  give  no  precipitate  with  basic  lead  acetate. 
A  measured  volume  of  the  filtrate  is  then  treated  with  measured  volumes  of  acetic 
acid  and  silver  nitrate  solution  to  completely  precipitate  any  chlorides  present. 
Filter  again  preferably  through  infusorial  earth.  Pass  hydrogen  sulphide  through 
the  filtrate  until  the  heavy  metals  are  completely  precipitated.  Filter  again.  Pass 
a  current  of  air  through  the  filtrate  to  remove  all  hydrogen  sulphide  (test  with  lead 
acetate  paper).  Neutralize  this  final  filtrate  with  calcium  carbonate  and  remove 
the  carbon  dioxide  with  a  current  of  air. 

The  neutral  filtrate  is  then  treated  with  an  amount  of  allantoin  reagent  in  excess 
of  that  required  to  precipitate  the  allantoin  as  indicated  by  a  preliminary  test. 
(The  allantoin  reagent  is  a  solution  containing  5  per  cent  mercuric  acetate  and  20 
per  cent  of  sodium  acetate.  The  reagent  when  used  must  be  clear.) 

Allow  to  stand  for  half  an  hour  (not  too  long)  and  then  filter.  A  measured 
amount  of  the  filtrate  is  taken  and  treated  with  about  10  c.c.  of  iron-ammonium 
alum  and  the  red  solution  decolorized  with  dilute  sulphuric  acid.  (The  solution  is  not 
completely  decolorized  but  retains  a  faint  greenish  tint.)  Any  calcium  sulphate 
precipitate  formed  at  this  point  may  be  disregarded.  Titrate  with  N/io  ammonium 
thiocyanate  solution  to  a  yellow  color,  which  increases  in  intensity  on  the  addition 
of  1-2  drops  more  of  solution.  The  titration  should  not  be  carried  out  in  artifi- 
cial light  and  some  practice  is  required  to  get  the  exact  end  point.  The  thiocyanate 
solution  should  be  standardized  occasionally  against  standard  silver  nitrate 
solution. 

Calculation. — One  c.c.  of  N/io  NH^SCN  solution  corresponds  to  0.00436  gram 
of  allantoin.  The  limit  of  error  of  the  method  is  about  5  mg.  for  the  daily  output 
of  allantoin.  In  the  calculation  of  course  all  losses  through  filtration,  etc.,  must 
be  considered. 

For  the  considerable  modifications  required  in  carrying  out  the  determination  on 
human  urine  with  its  very  low  content  of  allantoin  see  the  section  by  Wiechowski 
in  Neubauer-Huppert.1 

Interpretation. — Allantoin  may  be  found  in  very  small  amounts  in  human  urine 
(5-15  mg.  per  day),  appearing  to  be  mainly,  though  not  entirely,  exogenous  in  origin. 
It  forms,  however,  the  principal  end-product  of  the  purine  metabolism  of  practically 
all  mammals  other  than  man  and  the  anthropoid  apes.  Thus  over  90  per  cent  of 
the  purine-allantoin  nitrogen  excretion  of  the  dog,  the  cow,  and  the  pig  occurs  in 
this  form.  In  these  animals  its  origin  is  from  exogenous  and  endogenous  purines, 
and  its  excretion  is  influenced  by  much  the  same  factors  as  is  that  of  uric  acid  in 
man. 

1  Wiechowski:  Neubauer-Huppert:  Analyse  des  Hams,  Wiesbaden,  1913,  p.  1076. 


URINE  537 

2.  Determination  by  Difference. — Method  of  Plimmer  and  Skelton.1 — Allan- 
toin  is  transformed  into  urea  and  determined  as  such  by  the  acid-magnesium 
chloride  method  of  Folin  for  urea  in  urine.2  Urease,  however,  has  no  effect  upon 
allantoin.  Therefore,  determine  the  urea  +  allantoin  of  the  urine  according  to  Fo- 
lin's  procedure,  and  also  determine  the  true  urea  according  to  the  urease  method 
(see  Urea).  The  difference  between  the  results  thus  obtained  represents  allantoin. 
If  sugar  is  present  it  must  be  removed  before  applying  Folin's  procedure. 

Hippuric  Acid 

i.  Method  of  Folin  and  Flanders.3 — Principle. — The  hippuric  acid 
is  hydrolyzed  to  benzoic  acid  in  alkaline  solution  and  then  the  solution 
is  boiled  with  strong  nitric  acid  to  remove  pigments  and  emulsifying 
substances.  The  benzoic  acid  is  extracted  with  chloroform  and  ti- 
trated with  sodium  ethylate. 

Procedure. — Measure  100  c.c.  of  urine  into  a  porcelain  evaporating  dish  by 
means  of  a  pipette.  Add  10  c.c.  of  5  per  cent  NaOH  and  evaporate  to  dryness 
on  the  steam-bath.  Transfer  the  residue  to  a  500  c.c.  Kjeldahl  flask  by  means  of 
25  c.c.  of  water  and  25  c.c.  of  concentrated  HNOs.  Add  0.2  gram  of  copper 
nitrate,  a  couple  of  pebbles  or  glass  pearls  and  boil  very  gently  for  four  and  one- 
half  hours  over  a  micro-burner.  Fit  the  necks  of  the  flasks  with  condensers  of 
the  Hopkins  type  made  from  large  test-tubes  fitted  with  two-hole  rubber  stoppers, 
the  inlet  tubes  extending  near  the  bottom  of  the  test-tubes  while  the  outlet  tube 
is  shorter.  These  condensers  should  fit  rather  loosely.  A  good  current  of  water 
flowing  through  the  condensers  prevents  loss  of  benzoic  acid  or  change  in  con- 
centration of  the  nitric  acid. 

After  cooling,  rinse  the  condensers  down  with  25  c.c.  of  water  and  transfer  the 
contents  of  the  flask  to  a  500  c.c.  separatory  funnel,  with  the  aid  of  25  c.c.  more 
of  water.  The  total  volume  of  the  solution  is  now  100  c.c.  Add  to  the  solution 
sufficient  ammonium  sulphate  to  just  saturate  it  (about  55  grams).  Make  four 
extractions  with  freely  washed  chloroform,  using  50,  35,  25,  and  25  c.c.  portions. 
The  first  two  portions  may  be  used  to  further  rinse  out  the  Kjeldahl  flask. 

Collect  the  successive  portions  of  chloroform  in  another  separatory  funnel. 
Add  to  the  combined  extracts  100  c.c.  of  a  saturated  solution  of  pure  sodium  chlo- 
ride, to  each  liter  of  which  has  been  added  0.5  c.c.  of  concentrated  HC1.  Shake 
well,  draw  the  chloroform  into  a  dry  500  c.c.  Erlenmeyer  flask  and  titrate  with 
N/io  sodium  alcoholate,4  using  4  or  5  drops  of  phenolphthalein  as  an  indicator. 
The  first  distinct  end  point  should  be  taken,  although  it  may  fade  on  standing  a 
short  time. 

Calculation. — Multiply  the  number  of  cubic  centimeters  of  alcoholate  used  by 
the  factor  for  hippuric  acid  as  determined  by  standardization  to  obtain  the 
amount  of  hippuric  acid  in  the  100  c.c.  of  urine  used.  One  c.c.  of  exactly  N/io 

1  Plimmer  and  Skelton:  Bioch.  J.,  8,  70  and  641,  1914. 
1  Mathews  Physiological  Chemistry,  2d.  Ed.,  p.  953. 

3  Folin  and  Flanders:  Jour.  Biol.  Chem.,  n,  257,  1912. 

4  The  sodium  alcoholate  is  made  by  dissolving  2.3  grams  of  cleaned  metallic  sodium  in  i 
liter  of  absolute  alcohol.     It  is  advisable  that  it  be  slightly  weaker  rather  than  stronger 
than  tenth-normal.     It  may  be  standardized  against  pure  benzoic  acid  in  washed  chloro- 
form.    It  may  also  be  standardized  against  N/io  HC1  provided  the  alcoholate  solution 
contains  not  more  than  traces  of  carbonate. 


538  PHYSIOLOGICAL   CHEMISTRY 

sodium  alcoholate  is  equivalent  to  0.0179  gram  of  hippuric  acid.    Calculate  the 
daily  output  of  hippuric  acid  from  the  24-hour  volume. 

Interpretation. — The  average  excretion  of  hippuric  acid  by  a  normal 
adult  man  is  about  0.7  gram  per  day.  The  amount  is  increased  by 
the  ingestion  of  benzoic  acid  or  fruits  containing  it  (plums,  prunes, 
cranberries).  It  arises  in  part  apparently  from  putrefaction  products 
formed  in  the  intestine.  In  herbivora  it  is  often  the  most  abundant 
nitrogenous  constituent  of  the  urine. 

Glucose 

I.  Benedict's  Method.1 — Principle. — Benedict's  reagent  for  the  esti- 
mation of  reducing  sugars  contains  potassium  thiocyanate  as  well  as 
copper  sulphate,  and  in  the  presence  of  the  former  a  white  precipitate 
of  cuprous  thiocyanate  is  formed  on  reduction  instead  of  the  usual  red 
precipitate  of  cuprous  oxide.  The  small  amount  of  potassium  ferro- 
cyanide  also  aids  in  keeping  cuprous  oxide  in  solution.  As  the  pre- 
cipitate formed  is  white  the  loss  of  all  blue  tint  in  the  solution,  indicating 
complete  reduction  of  the  copper,  is  readily  observed.  The  alkali 
used  is  sodium  carbonate,  which  has  the  advantage  over  the  hydroxides 
in  that  there  is  less  danger  of  destruction  of  small  amounts  of  sugar. 
The  solution  also  has  the  great  advantage  of  being  stable  for  an  in- 
definite length  of  time.  The  method  is  recommended  for  simplicity 
and  accuracy. 

Procedure. — The  urine,  10  c.c.  of  which  should  be  diluted  with  water  to  100 
c.c.  (unless  the  sugar  content  is  believed  to  be  low,  when  it  may  be  used  un- 
diluted), is  poured  into  a  50  c.c.  burette  up  to  the  zero  mark.  Twenty-five  c.c.  of 
the  reagent2  are  measured  with  a  pipette  into  a  porcelain  evaporation  dish  (25-30 
cm.  in  diameter),  10  to  20  grams  of  crystallized  sodium  carbonate  (or  one-half  the 
weight  of  the  anhydrous  salt)  are  added,  together  with  a  small  quantity  of  pow- 
dered pumice  stone  or  talcum,  and  the  mixture  heated  to  boiling  over  a  free 
flame  until  the  carbonate  has  entirely  dissolved.  The  diluted  urine  is  now  run  hi 
from  the  burette,  rather  rapidly,  until  a  chalk-white  precipitate  forms  and  the 
blue  color  of  the  mixture  begins  to  lessen  perceptibly,  after  which  the  solution 

1  Benedict:  Jour.  Am.  Med.  Ass'n,  57,  1193,  1911. 

*  Copper  sulphate  (crystallized) 18 .  o  grams. 

Sodium  carbonate  (crystallized,  one-half  the  weight  of  the 

anhydrous  salt  may  be  used)  200. o  grams. 

Sodium  or  potassium  citrate . .    200.0  grams. 

Potassium  thiocyanate 125 .  o  grams. 

Potassium  ferrocyanide  (5  per  cent  solution) 5.0  c.c. 

Distilled  water  to  make  a  total  volume  of 1000.0  c.c. 

With  the  aid  of  heat  dissolve  the  carbonate,  citrate  and  thiocyanate  in  enough  water  to 
make  about  800  c.c.  of  the  mixture  and  filter  if  necessary.  Dissolve  the  copper  sulphate 
separately  in  about  100  c.c.  of  water  and  pour  the  solution  slowly  into  the  other  liquid,  with 
constant  stirring.  Add  the  ferrocyanide  solution,  cool  and  dilute  to  exactly  i  liter.  Of  the 
various  constituents,  the  copper  salt  only  need  be  weighed  with  exactness.  Twenty-five 
c.c.  of  the  reagent  are  reduced  by  50  mg.  of  glucose. 


URINE  539 

from  the  burette  must  be  run  in  a  few  drops  at  a  time,  until  the  disappearance  of 
the  last  trace  of  blue  color,  which  marks  the  end  point.  The  solution  must  be 
kept  vigorously  boiling  throughout  the  entire  titration.  If  the  mixture  becomes 
too  concentrated  during  the  process,  water  may  be  added  from  time  to  time  to 
replace  the  volume  lost  by  evaporation. 

Calculation. — The  calculation  of  the  percentage  of  sugar  hi  the  original  sample 
of  urine  is  very  simple.  The  25  c.c.  of  copper  solution  are  reduced  by  exactly  50 
mg.  of  glucose.  Therefore  the  volume  run  out  of  the  burette  to  effect  the  reduc- 
tion contained  50  mg.  of  the  sugar.  When  the  urine  is  diluted  i :  10,  as  in  the 
usual  titration  of  diabetic  urines,  the  formula  for  calculating  the  per  cent  of  the 
sugar  is  the  following : 

0.050 

— -—X 1 000  =  per  cent  hi  original  sample,  wherein  X 

A 

is  the  number  of  cubic  centimeters  of  the  diluted  urine  required  to  reduce  25  c.c. 
of  the  copper  solution. 

In  the  use  of  this  method  chloroform  must  not  be  present  during  the  titration. 
If  used  as  a  preservative  hi  the  urine  it  may  be  removed  by  boiling  a  sample  for 
a  few  minutes,  and  then  diluting  to  its  original  volume. 

Interpretation. — Sugar  in  the  urine  in  amounts  sufficient  to  be  de- 
tected by  the  commonly  employed  qualitative  tests  indicates  a  patho- 
logical condition,  unless  very  large  amounts  of  sugar  have  been  ingested 
just  previously,  in  which  case  the  condition  is  spoken  of  as  an  alimentary 
glycosuria.  Persistent  glycosuria  thus  indicates  diabetes  mellitus,  a 
disorder  in  which  the  amount  of  sugar  may  rise  as  high  as  10  per  cent 
and  averages  3-5  per  cent.  The  volume  of  urine  excreted  per  day  is 
usually  also  large  and  the  absolute  sugar  excretion  may  thus  be  very 
great  (100  grams  of  glucose  per  day  are  not  uncommon).  The  quantita- 
tive methods  for  the  estimation  of  sugar  in  urine  enable  us  to  deter- 
mine the  severity  of  the  disorder  as  well  as  to  follow  its  course  under 
treatment,  etc. 

2.  Benedict's  Micro  -  Method . — Principle.  — See  Benedict's 
Method  above. 

Procedure. — Five  c.c.  of  Benedict's  volumetric  solution  are  pipetted  into  a 
test  tube  (25  X  150  mm.)  and  i  to  2  gm.  of  sodium  carbonate  added.  (If 
preferred  a  25  c.c.  Erlenmeyer  flask  may  be  employed,  instead  of  the  test  tube, 
and  the  flask  placed  over  a  wire  gauze.)  The  solution  is  now  brought  to  a 
vigorous  boil  with  continued  gentle  agitation,  the  tube  being  held  in  the  left 
hand,  employing  a  folded  paper  as  a  test  tube  holder.  With  the  right  hand  the 
urine  is  run  in,  a  drop  at  a  time,  until  a  chalk-white  precipitate  begins  to  form. 
The  urine  is  now  run  in  more  slowly  until  one  drop  dissipates  the  last  trace  of 
color,  indicating  the  end  point  in  the  reaction. 

f'jj  Calculation. — Since  the  5  c.c.  of  the  Benedict  solution  require  exactly  10  mg. 
(o.oi  gm.)  of  glucose  for  reduction,  the  calculation  may  be  made  very  simple. 

100 

The  following  formula  may  be  used :   -  X  o.oi  =  glucose  in  per 

Burette  reading 

cent,  or  more  simply,  the  urine  used  in  c.c.  may  be  divided  into  i. 


540  PHYSIOLOGICAL   CHEMISTRY 

With  this  method  the  urine  should  be  diluted  when  the  sugar  content  ex- 
ceeds 2.5  per  cent.  Under  0.5  per  cent  of  sugar  the  figures  are  likewise  inac- 
curate, and  here  Benedict's  colorimetric  method  of  estimating  the  sugar  content 
of  normal  urine  should  be  used. 

Interpretation. — See  Benedict's  Method  above. 

3.  Folin-McEllroy-Peck  Method.1  Principle. — The  method  is  a 
titration  procedure  depending  upon  the  use  of  an  alkaline  copper 
solution  in  which  the  cupric  hydroxide  is  held  in  solution  by  means  of 
phosphate  instead  of  the  customary  tartrates,  citrates,  or  glycerol. 

The  method  is  applicable  to  the  determination  of  lactose  in  milk. 

Procedure. — Place  5  c.c.  of  an  acidified  5.9  per  cent  copper  sulphate  solution2 
in  a  large,  hard  glass  test  tube  and  add  approximately  i  c.c.  of  20  per  cent  sodium 
carbonate  solution.  Shake  for  a  moment  and  add  4  to  5  gms.  of  phosphate - 
carbonate -thiocyanate  mixture3  and  a  small  pebble.  Heat  gently  with  shaking 
until  all  the  salts  have  dissolved  except  for  a  few  isolated  particles  of  sodium 
carbonate.  A  clear  solution  is  usually  obtained  in  less  than  i  minute  at  tem- 
peratures which  need  not  exceed  6o°C.  From  a  burette4  add  undiluted  urine 
(0.4  c.c.  to  i.o  c.c.)  heat  fairly  rapidly  to  boiling  and  boil  very  gently  for  2  minutes. 
With  the  full  required  amount  of  sugar  present  at  the  beginning  (the  5  c.c.  of 
copper  solution  are  reduced  by  25  mg.  of  glucose),  the  boiling  solution  becomes 
suddenly  turbid  within  5  seconds  after  the  boiling  point  has  been  reached.  If, 
within  the  first  15  seconds  of  boiling,  the  contents  of  the  test  tube  do  not  thus 
suddenly  become  filled  with  the  cuprous  thiocyanate  precipitate,  then  less  than 
half  the  required  amount  of  sugar  has  been  added  and  more  urine  should  be 
added  without  further  delay  and  the  gentle  boiling  be  continued.  On  the  other 
hand,  when  an  excess  of  sugar  has  been  inadvertantly  added  at  the  beginning  of 
the  process  it  is  advisable  to  note  the  time  required  for  complete  decolorization 
of  the  copper,  for  this  time  (see  table)  can  serve  as  a  guide  to  the  quantity  of 
solution  to  be  introduced  at  the  next  titration. 

The  only  restriction  called  for  hi  the  final  titration  is  that  complete  reduction 
must  not  occur  in  less  than  4  minutes  of  boiling.  It  makes  practically  no  diff  er- 

1Folin  and  McEllroy:  Jour.  Biol.  Chem.,  33  513,  1918;  Folin  and  Peck:  Jour.  Biol. 
Chem.,  38,  287,  1919. 

2Prepare  this  acidified  copper  sulphate  solution  by  dissolving  59  gm.  of  CuSO4-i2H2O  in 
water  together  with  2  c.c.  of  concentrated  sulphuric  acid  and  making  up  to  i  liter.  Five 
c.c.  of  this  solution  correspond  to  25  mg.  of  glucose  or  fructose,  45  mg.  of  anhydrous 
maltose,  or  40.4  mg.  of  anhydrous  lactose. 

3To  prepare  the  phosphate-carbonate-thiocyanate  mixture  powder  in  a  large  mortar 
200  gm.  of  crystallized  disodium  phosphate  (HNa2PO4-i2H2O)  and  sprinkle  over  it  about 
50  gm.  of  sodium  thiocyanate  (or  60  gm.  of  potassium  thiocyanate).  Mix  for  10  minutes 
with  pestle  and  spoon,  giving  a  uniform  semi-liquid  paste.  Add  about  120  gm.  of  mono- 
hydrated  sodium  carbonate  (or  100  to  no-gm.  of  anhydrous  carbonate)  and  mix  with  pestle 
and  spoon  until  a  rather  fluffy,  granular  powder  is  obtained.  To  test  the  completeness 
of  the  mixing  add  5  gm.  of  the  powder  to  5  c.c.  of  the  copper  solution;  if  any  black  specks 
are  formed,  even  temporarily,  the  mixing  is  incomplete.  A  certain  amount  of  green  color 
is,  however,  practically  unavoidable  when  this  test  is  applied.  If  no  black  coloration  is 
obtained  allow  the  mixture  to  stand  in  the  mortar  for  a  few  hours  or  over  night  (covered 
with  paper)  mix  once  more  and  transfer  to  bottles.  In  stoppered  bottles  the  mixture  keeps 
indefinitely. 

4Special  5  c.c.  sugar  burettes  graduated  in  0.02  c.c.  together  with  accessory  capillary 
tips  for  delivering  very  small  drops  are  made  by  the  Emil  Greiner  Company,  New  York. 


URINE  541 

ence  in  the  result  (at  the  most  i  per  cent)  if  the  boiling  period  be  prolonged  to 
8  or  9  minutes,  provided  that  the  boiling  be  gentle  enough  to  prevent  excessive 
concentration.  The  volume  of  the  solution  in  the  test  tube  should  not  become 
less  than  6  to  7  c.c. 

Calculation. — Divide   2.5   by  the  volume  of  urine  taken  (whether  this  is 
several  c.c.  or  a  fraction  of  i  c.c.)  to  get  the  per  cent  of  sugar  in  the  urine. 

TIME  OF  BOILING  REQUIRED  FOR  COMPLETE  REDUCTION  OF    COPPER 
SOLUTION  BY  AN  EXCESS  OF  GLUCOSE 


Glucose 

Boiling  time 

mg. 

minute                                         second 

50 

0 

25- 

40 

o 

40 

35 

o 

55 

30 

i 

20  to  30 

27-5 

i 

30  to  55 

Interpretation. — See  page  539. 

4.  Fehling's  Method. — Principle. — Diluted  urine  is  run  into  a 
measured  amount  of  Fehling's  solution  at  the  boiling-point  until  all 
of  the  copper  it  contains  is  reduced  as  indicated  by  the  loss  of  blue  color. 
This  method  has  several  disadvantages  over  Benedict's  method.  The 
end  point  is  difficult  to  determine  and  the  mixed  solution  is  unstable. 
It  gives  less  accurate  results. 

Procedure. — Place  10  c.c.  of  the  urine  under  examination  in  a  100  c.c.  volu- 
metric flask  and  make  the  volume  up  to  100  c.c.  with  distilled  water.  (If  the 
urine  contains  less  than  0.5  per  cent  of  sugar  it  may  be  used  without  dilution.  A 
concentration  of  about  0.5  per  cent  is  the  most  satisfactory  for  this  titration.) 
Thoroughly  mix  this  diluted  urine  by  pouring  it  into  a  beaker  and  stirring  with 
a  glass  rod,  then  transfer  a  portion  of  it  to  a  burette  which  is  properly  supported 
in  a  clamp. 

Now  place  10  c.c.  of  Fehling's  solution1  hi  a  small  beaker,  dilute  it  with  approxi- 
mately 40  c.c.  of  distilled  water,  heat  to  boiling,  and  observe  whether  decomposi- 
tion of  the  Fehling's  solution  itself  has  occurred  as  indicated  by  the  production  of 
a  turbidity.  If  such  turbidity  is  produced  the  Fehling's  solution  is  unfit  for  use. 
Clamp  the  burette  containing  the  dilute  urine  immediately  over  the  beaker  and 
carefully  allow  from  0.5-1  c.c.  of  the  diluted  urine  to  flow  into  the  boiling  Fehl- 
ing's solution.  Bring  the  solution  to  the  boiling-point  after  each  addition  of 
urine  and  continue  running  the  urine  from  the  burette,  0.5-1  c.c.  at  a  tune,  as  in- 
dicated, until  the  Fehling's  solution  is  completely  reduced,  i.e.,  until  all  the  cupric 
oxide  in  solution  has  been  precipitated  as  cuprous  oxide.  This  point  will  be 
indicated  by  the  absolute  disappearance  of  all  blue  color.  When  this  end  point 

1  Directions  for  the  preparation  of  Fehling's  solution  are  given  in  a  note  at  the  bottom 
of  p.  25. 


542  PHYSIOLOGICAL   CHEMISTRY 

is  reached  note  the  number  of  cubic  centimeters  of  diluted  urine  used  in  the  proc- 
ess and  calculate  the  percentage  of  dextrose  present,  in  the  sample  of  urine 
analyzed,  according  to  the  method  given  below. 

This  is  a  satisfactory  method,  the  main  objection  to  its  use  being  the  un- 
certainty attending  the  determination  of  the  end-reaction,  i.e.,  the  difficulty  with 
which  the  exact  point  where  the  blue  color  finally  disappears  is  noted.  Several 
means  of  accurately  fixing  this  point  have  been  suggested,  but  they  are  prac- 
tically all  open  to  objection.  As  good  a  "check"  as  any,  perhaps,  is  to  filter 
a  few  drops  of  the  solution  through  a  double  paper,  after  the  blue  color  has 
apparently  disappeared,  acidify  the  filtrate  with  acetic  acid  and  add  potassium 
ferrocyanide.  If  the  copper  of  the  Fehling's  solution  has  been  completely 
reduced,  there  will  be  no  color  reaction,  whereas  the  production  of  a  brown  color 
indicates  the  presence  of  unreduced  copper.  Harrison  has  recently  suggested 
the  following  procedure  to  determine  the  exact  end  point :  To  about  i  c.c.  of  a 
starch  iodide  solution1  in  a  test-tube  add  2-3  drops  of  acetic  acid  and  introduce 
into  the  acidified  mixture  1-2  drops  of  the  solution  to  be  tested.  Unreduced 
copper  will  be  indicated  by  the  production  of  a  purplish-red  or  blue  color  due  to 
the  liberation  of  iodine. 

It  is  ordinarily  customary  to  make  at  least  three  determinations  by  Fehling's 
method  before  coming  to  a  final  conclusion  regarding  the  sugar  content  of  the 
urine  under  examination. 

Calculation. — Ten  c.c.  of  Fehling's  solution  is  completely  reduced  by  0.05 
gram  of  dextrose.2  If  y  represents  the  number  of  cubic  centimeters  of  undiluted 
urine  (obtained  by  dividing  the  burette  reading  by  10)  necessary  to  reduce  the 
10  c.c.  of  Fehling's  solution,  we  have  the  following  proportion : 

y :  0.05 :  :  100 :  x  (percentage  of  dextrose). 

Interpretation. — See  page  539. 

5.  Bang's  Method.3 — Principle. — The  solution  to  be  tested  is  boiled 
with  alkaline  cupric  chloride  solution  containing  thiocyanate  and  potas- 
sium chloride.  The  cupric  salt  under  these  conditions  is  reduced  to 
the  cuprous  form  without  any  precipitation  taking  place.  The  re- 
duced copper  is  titrated  with  standard  iodine  solution  using  starch  as 
an  indicator.  The  titration  reaction  is  as  follows: 

CuCl  +  I  +  K2C03  =  CuC03  +  KC1  +  KI. 

Procedure. — A  100  c.c.  Jena  flask  with  a  straight  neck,  the  flange  of  which  has 
been  cut  off,  is  used  for  the  boiling  procedure.  Over  the  neck  of  the  flask  place 
a  piece  of  tight  fitting  rubber  tubing  sufficiently  long  (about  2  inches),  so  that  it 

1  The  starch-iodide  solution  may  be  prepared  as  follows:  Mix  o.i  gram  of  starch  with 
cold  water  in  a  mortar  and  pour  the  suspended  starch  granules  into  75-100  c.c.  of  boiling 
water,  stirring  continuously.     Cool  the  starch  paste,  add  20-25  grams  of  potassium  iodide 
and  dilute  the  mixture  to  250  c.c.    This  solution  deteriorates  upon  standing,  and  there- 
fore must  be  freshly  prepared  as  needed. 

2  The  values  for  certain  other  sugars  are  as  follows: 

Lactose 0.0676  gram. 

Maltose 0.074    gram. 

Invert  sugar 0.0475  gram. 

3  Bang:  Biochem.  Zeit.,  49,  i,  1913. 


URINE  543 

may  be  provided  with  a  pinch  cock  or  clamp  to  shut  off  the  contents  of  the  flask 
from  the  outside  air  (see  Fig.  91,  page  289). 

Introduce  into  the  flask  o.i  to  2.0  c.c.  (or  more)  of  the  sugar  solution  contain- 
ing not  more  than  10  mg.  of  glucose.  Then  add  55  c.c.  of  the  diluted  copper 
solution.1  Heat  over  an  asbestos  gauze  with  a  flame  standardized  to  bring  the 
solution  to  the  boiling-point  in  from  3  1/2-3  3/4  minutes.  Boil  for  exactly  3 
minutes,  being  prepared  to  close  the  flask  with  the  pinch-cock  at  the  end  of  the 
3  minutes.  Remove  from  the  flame  and  at  once  cool  under  the  tap  to  room  tem- 
perature. Remove  the  rubber  tubing,  add  to  the  contents  of  the  flask  0.5-1 
c.c.  of  the  starch  solution  (i  gram  of  soluble  starch  in  100  c.c.  of  saturated  KC1 
solution,  which  keeps  indefinitely).  Titrate  with  the  standard  iodine  solution1 
run  in  from  an  accurate  burette  with  a  glass  stopcock.  When  the  iodine  starch 
color  appears  throughout  the  solution  rotate  gently  and  let  stand  a  few  seconds. 
The  end  point  is  reached  when  the  blue  color  endures  for  10-20  seconds.  It  is 
preferable  to  carry  out  the  titration  in  an  atmosphere  of  carbon  dioxide,  main- 
tained by  means  of  a  delivery  tube  hung  over  the  side  of  the  flask.  Otherwise 
the  titration  must  be  carried  out  rapidly  to  prevent  reoxidation  by  the  oxygen  of 
the  air. 

Calculation.— Divide  the  number  of  cubic  centimeters  of  N/ioo  iodine  solu- 
tion used  in  the  titration  by  2.7  to  obtain  the  number  of  milligrams  of  glucose  in 
the  amount  of  solution  used. 

This  method  is  suitable  for  urine  analysis.  The  urine  must  however  be  free 
from  albumin  and  as  urine  contains  substances  reacting  slowly  with  iodine  the 
end  point  must  be  taken  when  the  blue  color  persists  for  about  10  seconds  and  any 
slow  decolorization  disregarded. 

Interpretation. — See  page  539. 

6.  Peters'  Method.2 — Principle. — The  sugar  solution  is  boiled  with  an  alkaline 
copper  solution  under  rigidly  standardized  conditions  and  after  nitration  the  un- 
reduced copper  is  determined  by  adding  potassium  iodide  and  titrating  the  liber- 
ated iodine  with  standard  thiosulphate  solution. 

Procedure. — A .  The  Heating  Power. — It  is  necessary  to  standardize  the  heating 
power  of  the  flame  used  in  the  reduction  process.  A  200  c.c.  Erlenmeyer  flask  of 
Jena  glass  and  of  about  6  cm.  basal  diameter  is  used.  This  bears  a  two-hole  rubber 
stopper,  one  hole  of  which  carries  a  thermometer.  The  lower  end  of  the  thermome- 

1  Copper  Solution. — Stock  Solution. — Dissolve  first  160  grams  potassium  bicarbonate, 
100  grams  potassium  carbonate  and  66  grams  of  potassium  chloride  with  about  700  c.c. 
of  distilled  water  in  a  liter  flask.     Pure  salts  must  be  used  in  each  case.    As  the  bicarbonate 
is  difficultly  soluble  it  should  be  finely  powdered  and  brought  into  solution  first,  preferably 
with  warming  to  3O°C.     The  KC1  is  then  dissolved  and  finally,  with  cooling,  the  carbonate. 
Then  add  100  c.c.  of  a  4.4  per  cent  solution  of  pure  crystalline  CuSO^sH^O.     Fill  to  the 
mark  with  distilled  water.     Mix  without  strong  shaking  and  let  stand  for  24  hours  before 
using. 

Dilute  Copper  Solution. — Dilute  300  c.c.  of  the  stock  solution  to  1000  c.c.  Mix  with 
only  gentle  shaking.  Allow  to  stand  for  several  hours  before  using. 

Standard  Iodine  Solution. — The  N/ioo  iodine  solution  is  made  by  dilution  of  N/io 
iodine  solution  (see  appendix)  with  boiled  out  distilled  water.  The  solution  is  stable  for 
three  months  if  kept  in  a  dark  bottle.  It  may  also  be  prepared  daily  from  KI  and  KIO«. 
Introduce  into  a  100  c.c.  flask  about  i  c.c.  of  2  per  cent  KIO3,  and  2-2.5  grams  of  KI  and 
then  exactly  10  c.c.  of^N/io  HC1.  The  HC1  liberates  an  equivalent  amount  of  iodine  (sul- 
phuric acid  is  less  desirable).  Make  to  100  c.c.  with  distilled  water  and  mix. 

2  Peters:  /.  Am.  Ghent.  Soc.,  34,  928,  1912;  34,  422,  1912. 


544  PHYSIOLOGICAL   CHEMISTRY 

ter  should  extend  to  about  2  mm.  from  the  bottom^^ie  flask  and  the  35°  mark 
on  the  thermometer  stem  should  be  visible  above  tl^^Hjpper.  The  flask  is  placed 
on  an  asbestos  gauze  supported  by  an  adjustable  rin^tand.  A  Bunsen  or  Meker 
burner  is  used  and  is  placed  at  from  3-5  cm.  beneath  the  lower  surface  of  the  asbestos 
gauze.  Use  a  large  flame  and  allow  the  ring  and  gauze  to  become  thoroughly 
heated.  Then  place  the  flask,  into  which  60  c.c.  of  distilled  water  has  been  intro- 
duced, in  the  center  of  the  gauze  and  observe  the  time  required  for  the  temperature 
in  the  flask  to  rise  from  35  to  95°C.  By  several  trials  the  flame  and  position  of  the 
gauze  are  so  adjusted  that  it  requires  (within  a  few  seconds  either  way)  just  120 
seconds  for  the  temperature  to  rise  from  35-95°C.  This  standard  flame  is  then 
used  in  the  determinations  which  follow. 

B.  The  Reduction  Process. — Into  a  200  c.c.  Jena  Erlenmeyer  flask  fitted  as 
above,  introduce  20  c.c.  of  alkaline  tartrate  solution,1  20  c.c.  of  the  copper  sulphate 
solution1  and  the  sugar  solution  to  be  analyzed  which  should  first  be  made  up  to 
20  c.c.  so  that  the  total  volume  of  the  fluid  in  the  reduction  flask  is  always  60  c.c. 
Place  the  flask  over  the  standard  flame  and  note  when  the  temperature  of  the  mix- 
ture reaches  95°C.  Allow  to  boil  for  exactly  20  seconds  after  the  temperature 
reaches  95°.  Then  the  flask  is  promptly  removed  with  the  stopper  still  in  place 
and  held  under  the  tap  for  a  moment  to  stop  the  reduction  but  not  to  cool  the  mix- 
ture more  than  a  few  degrees  below  the  boiling-point.  Filter  hot  through  a  pre- 
viously prepared  Gooch  crucible  with  a  heavy  asbestos  mat  through  which  sufficient 
of  a  suspension  of  talcum  has  been  filtered  so  that  with  suction,  not  a  stream  but  a 
rapid  succession  of  drops  conies  through  the  filter.  (A  calcium  chloride  tube 
packed  with  glass  wool  and  asbestos  may  also  be  used.)  The  suction  flask  should 
have  a  capacity  of  about  200  c.c.  so  that  the  titration  may  be  carried  out  in  it  di- 
rectly. Wash  the  filter,  with  a  fine  stream  of  water  using  not  more  than  15-20  c.c. 
of  water  in  all.  To  the  filtrate  add  4  c.c.  of  concentrated  sulphuric  acid  and  cool 
to  2o°C.  Add  6-7  c.c.  of  a  saturated  solution  of  potassium  iodide.  Titrate  the 
liberated  iodine  with  standard  thiosulphate  solution,2  adding  a  few  drops  of  a  solu- 
tion of  soluble  starch  as  an  indicator  near  the  close  of  the  titration.  The  "spot 
test"  may  be  used  in  determining  the  end  point.  As  long  as  a  drop  of  thiosulphate 
produces  a  perceptible  white  area  in  falling  upon  the  quiet  solution  the  end  point 
has  not  been  reached.  The  chocolate-brown  color  of  the  mixture  changes  to  a 
light  cream  white  as  the  last  necessary  drop  of  thiosulphate  is  added. 

A  blank  should  be  run  in  exactly  the  same  way  but  with  the  omission  of  the 
sugar  solution. 

Calculation. — Subtract  the  number  of  cubic  centimeters  of  thiosulphate  re- 
quired for  the  titration  of  unreduced  copper  from  the  number  of  cubic  centimeters 
required  for  the  blank.  This  gives  the  amount  of  thiosulphate  equivalent  to  copper 

1  Copper  Solution. — Dissolve  34.639  grams  of  highest  purity  crystallized  copper  sulphate 
(Kahlbaum's  "zur  Analyse  mit  Garantieschein)  in  water  to  make  500  c.c. 

Alkaline  Tartrate  Solution. — Dissolve  173  grams  of  sodium  potassium  tartrate  and  125 
grams  of  potassium  hydroxide  in  water  to  make  500  c.c. 

2  N/5  Sodium  Thiosulphate. — Dissolve  about  50  grams  of  ordinary  c.p.  sodium  thio- 
sulphate or  exactly  49.66  grams  of  the  pure,  dry,  recrystallized  salt,  in  enough  boiled-out 
distilled  watec  to  make  a  liter.     Allow  to  stand  for  several  days.    The  solution  should  be 
standardized  against  the  copper  solution  prepared  as  above.     For  this  purpose  introduce 
20  c.c.  of  the  copper  solution  into  a  200  c.c.  Erlenmeyer  flask,  add  20  c.c.  of  30  per  cent 
acetic  acid  and  40  c.c.  of  water.    Add  about  7  grams  of  a  saturated  solution  of  KI  and 
titrate  with  the  thiosulphate  using  starch  as  an  indicator.     Calculate  the  equivalent  of  i 
c.c.  of  thiosulphate  in  Cu.     One  c.c.  of  the  copper  sulphate  solution  contains  17.647  mg. 
of  Cu.     The  thiosulphate  remains  constant  for  some  months.     It  should  be  kept  in  a 
dark  bottle. 


URINE 


545 


reduced.  Multiply  this  result  by  the  value  of  i  c.c.  of  thiosulphate  expressed  as 
Cu,  and  obtain  the  number  of  milligrams  of  copper  reduced.  Then  by  consulting 
the  table  of  values  (below)  determine  the  weight  of  glucose  equivalent  to  this 
amount  of  copper. 

Cole1  has  determined  the  copper  values  for  lactose  using  this  method  exactly 
as  outlined.  He  has  also  suggested  the  following  empirical  formula  which  agrees 
well  with  the  values  derived  from  his  tables 

Mg.  anhydrous  lactose  =  1.25  +  0.778  X  mg.  Cu. 
Interpretation. — See  page  539. 

TABLE  FOR  THE  DETERMINATION  OF  GLUCOSE 

According  to  Peters 


Copper, 

Glucose 

—  «  4.?  «. 

Copper, 

Glucose 

Tlf  1/1 

Glucose 

mg. 

ratio 
Cu 

Glucose 

mg. 

Cu 

i 

1.2 

0.833 

60 

, 
"5-5 

0.522 

2 

2.8 

0.714 

70 

134-4 

0.522 

5 

8.2 

0.610 

80 

152.9 

0.522 

8 

13.8 

0.580 

90 

171.0 

0.522 

i° 

17.4 

0.575 

IOO 

191.6 

0.522 

IS 

27.7 

0.542 

no 

208.9 

0.527 

20 

37-1 

0-539 

120 

228.1 

0.526 

25 

48.1 

0.522 

•135 

255-0 

0.529 

30 

57-3 

0.522 

ISO 

280.8 

0-534 

35 

67.6 

0.522 

165 

306.8 

0.538 

40 

76.2 

0.522 

180 

330.5 

0-545 

45 

86.0 

0.522 

200 

349-6 

0.572 

50 

96.0 

0.522 

7.  Bertrand's  Method.2  Principle.  —  The  sugar  is  boiled  with  alkaline  copper 
sulphate  solution  and  the  precipitated  cuprous  oxide  filtered  off,  dissolved  in  an  acid 
solution  of  ferric  sulphate  and  the  resultant  ferrous  salt  titrated  with  potassium 
permanganate.  This  method  of  titrating  cuprous  oxide  may  be  conveniently  used 
where  other  reduction  procedures  such  as  that  of  Peters  or  of  Munson  and  Walker,1 
have  been  employed.  In  this  case  the  tables  corresponding  to  the  particular 
method  and  not  the  Bertrand  tables  must  be  consulted  in  calculating  the  sugar 
equivalent. 

The  following  reactions  are  involved  in  the  Bertrand  titration: 


Cu2O  -f-  Fe2(SO4)3  +  H2SO4  =  2CuS04  +  2FeS04  +  H2O 
ioFeS04  +  2KMnO4  +  8H2SO4  -  5Fe2(S04),  +  K2SO4  +  2MnS04 


8H20. 


Procedure.  —  Introduce  into  an  Erlenmeyer  flask  of  150  c.c.  capacity,  20  c.c.  of 
the  sugar  solution  (of  a  concentration  of  0.5  per  cent  or  less),  20  c.c.  of  the  copper 


1  Cole:  Biochem.  /.,  8,  134,  1914. 

1  Bertrand:  Bull.  Soc.  Chim.  de  France,  35,  1285,  1906. 

3  Munson  and  Walker:  Bull.,  107,  U.  S.  Dept.  of  Agriculture. 

55 


PHYSIOLOGICAL   CHEMISTRY 


TABLE  FOR  THE  DETERMINATION  OF  REDUCING  SUGARS 

According  to  Bertrand 


Sugar  in  mg. 

Glucose 
Cu 

Invert  sugar 
Cu 

Galactose 
Cu 

Maltose 
Cu 

Lactose 
Cu 

10 

20.4 

20.6 

19-3 

II.  2 

14.4 

ii 

22.4 

22.6 

21  .  2 

12.3 

15-8 

12 

24.3 

24.6 

23.0 

13-4 

17.2 

13 

26.3 

26.5 

24.9 

14-5 

18.6 

*4 

28.3 

28.5 

26.7 

15-6 

20.0 

IS 

30-2 

30-5 

28.6 

I6.7 

21.4 

16 

32.2 

32.5 

30.5 

17.8 

22.8 

17 

34-2 

34-5 

32-3 

18.9 

24.2 

18 

36.2 

36.4 

34-2 

2O.  O 

25-6 

?9 

38.1 

38.4 

36.0 

21.  I 

27.0 

20 

40.1 

40.4 

37-9 

22.2 

28.4 

21 

42.0 

42.3 

39-7 

23-3 

29.8 

22 

43-9 

44.2 

41.6 

24-4 

3LI 

23 

45-8 

46.1 

43-4 

25-5 

32.5 

24 

47-7 

48.0 

45-2 

26.6 

33-9 

25 

49.6 

49-8 

47.0 

27.7 

35-2 

26 

51-5 

51-7 

48.9 

28.9 

36.6 

27 

53-4 

53-6 

50-7 

30.0 

38.0 

28 

55-3 

55-5 

52.5 

3I-I 

39-4 

29 

57-2 

57-4 

54-4 

32.2 

40.7 

30 

59-1 

59-3 

56.2 

33-3 

42.1 

31 

60.9 

6l.T 

58.0 

34-4 

43-4 

32 

62.8 

63.0 

59-7 

35-5 

44-8 

33 

64.6 

64.8 

61.5 

36.5 

46.1 

34 

66.5 

66.7 

63-3 

37.6 

47-4 

35 

68.3 

68.5 

65.0 

38.7 

48.7 

36 

70.1 

70.3 

66.8 

39-8 

50-1 

37 

72.0 

72.2 

68.6 

40.9 

51-4 

.      3§ 

73-8 

74.0 

70.4 

41.9 

52.7 

39 

75-5 

75-9 

72.1 

43-0 

54-1 

40 

77-5 

77-7 

73-9 

44.1 

55-4 

4i 

79-3 

79-5 

75-6 

45-2 

56.7 

42 

81.1 

81.2 

77-4 

46.3 

58.0 

43 

82.9 

83.0 

79.1 

47-4 

59-3 

44 

84.7 

84.8 

80.8 

48.5 

60.6 

45 

86.4 

86.5 

82.5 

49-5 

61.9 

46 

88.2 

88.3 

84.3 

50.6 

63-3 

47 

90.0 

90.1 

86.0 

Si-7 

64.6 

48 

91.8 

91.9      . 

87.8 

52-8 

65.9 

»#9_-  - 
Yo 

--J&3.6 
(95-4 

93-6 
95-4 

89.5 
91.2 

53-9 
55-0 

67.2 
68.5 

Si 

97-1 

97.1 

92.9 

56.1 

69.8 

52 

98.9 

98.8 

94.6 

57-i 

71.1 

53 

100.6 

100.6 

96.3 

58.2 

72.4 

54 

102.3 

102.3 

98.0 

59-3 

73-7 

55 

104.1 

104.0 

99-7 

60.3 

74-9 

56 

105.8 

ioS-7 

101.5 

61.4 

76.2 

URINE 


547 


TABLE  FOR  THE  DETERMINATION  OF  REDUCING  SUGARS.—  (Continued) 

According  to  Bertrand 


Sugar  in  mg. 

Glucose 

Cu       . 

Invert  sugar 
Cu 

Galactose 
Cu 

Maltose          Lactose 
.Cu                  Cu 

57 

•    1 
107.6 

107.4 

103.2                 62.5 

77-5 

58 

109.3 

109.  2 

104.9 

63-5 

78.8 

59 

in.  i 

IIO.9 

106.6 

64.6 

80.  i 

60 

112.  8 

112.  6 

108.3 

65-7 

81.4 

61 

"4-5 

H4-3 

IIO.O 

66.8 

82.7 

62 

116.2 

"5-9 

in.  6 

67.9 

83.9 

63 

117.9 

II7.6 

"3-3 

68.9 

85.2 

64 

119.6 

II9.2 

115.0 

70.0 

86.5 

65 

121.3 

I2O-9 

116.6 

71.1 

87.7 

66 

123.0 

122.6 

118.3 

72.2 

89.0 

67 

124.7 

124.2 

I2O.O 

73-3 

90.3 

68 

126.4 

125-9 

I2I.7 

74-3 

91.6 

69 

128.1 

I27.S 

123.3 

75-4 

92.8 

70 

129.8 

129.2 

125.0 

76.5 

94.1 

7i 

131-4 

I30-8 

126.6* 

77-6 

95-4 

72 

133.1 

132.4 

128.3 

78.6 

96.6 

73 

134.7 

134-0 

130.0 

79-7 

97-9 

74 

136.3 

135-6 

I3I.5 

80.8 

99.1 

75 

137.9 

137.2 

I33.I 

81.8 

100.4 

76 

139.6 

138.9 

134.8 

82.9 

101.7 

77 

141.2 

140.5 

^36.4 

84.0 

102.9 

78 

142.8 

I42.I 

138.0 

85.1 

104.2 

79 

144.5 

143-7 

139-7 

86.1 

105.4 

80 

146.1 

145-3 

I4I.3 

87.2 

106.7 

81 

147.7 

146.9 

•142.9 

83-3 

107.9 

82 

149-3 

148.5 

144.6 

89-4 

109.2 

83 

150.9 

150.0 

146.2 

90.4 

110.4 

84 

152.5 

I5I.6 

147-8 

9i-5 

111.7 

85 

154.0 

153-2 

149.4 

92.6 

112.9 

86 

155.6 

154.8 

ISI.I 

93-7 

114.1 

87 

157.2 

156.4 

152.7 

94-8 

"5-4 

88 

158.8 

157-9 

154-3 

95-3 

116.6 

89 

160.4 

159-5 

156.0 

96.9 

117.9 

90 

162.0 

161.1 

157-6 

98.0 

119.1 

9i 

163.6 

162.6 

159.2 

99.0 

120.3 

92 

165.2 

164.2 

160.8 

100.  I 

121.  6 

93 

166.7 

165-7 

162.4 

IOI.I 

122.8 

94 

168.3 

167.3 

164.0 

IO2.2 

I24.O 

95 

169.9 

168.8       . 

165.6 

103.2 

125.2 

96 

171.5 

170.3 

167.2 

104.2 

126.5 

97 

173.1 

171.9 

168.8 

105.3 

127.7 

98 

174.6 

173-4 

170.4 

106.3 

128.9 

99 

176.2 

175-0 

I72.O 

107.4 

130.2 

TOO 

177.8 

176.5 

173.6 

108.4 

I3I-4 

548  PHYSIOLOGICAL   CHEMISTRY 

solution1  and  20  c.c.  of  the  alkaline  tartrate  solution.1  Heat  to  boiling  over  an 
asbestos  gauze  and  boil  gently  for  exactly  three  minutes.  Let  stand  a  moment  that 
the  copper  oxide  may  settle  and  then  filter  with  suction  through  a  Gooch  crucible 
with  a  heavy  asbestos  mat  (or  a  calcium  chloride  tube  with  successive  layers  of 
glass  wool,  coarse  asbestos  and  fine  asbestos  wool)  into  a  flask  of  about.  150  c.c. 
capacity.  Wash  the  residue  in  the  flask  twice  by  decantation  with  a  little  hot 
water  pouring  the  supernatant  liquid  through  the  filter.  Throw  away  the  clear 
filtrate,  rinse  the  flask  and  replace  it.  To  the  flask  containing  the  cuprous  oxide 
add  5-20  c.c.  of  the  acid  ferric  sulphate  solution.1  A  green  solution  containing 
ferrous  sulphate  is  formed.  Pour  through  the  filter  together  with  a  little  more  of 
the  acid  solution  if  necessary  to  completely  dissolve  the  copper  oxide.  Wash  flask 
and  filter  with  a  little  water.  Titrate  the  filtrate  with  standard  potassium  per- 
manganate solution1  to  a  rose  color.  The  procedure  should  be  carried  out  as  rapidly 
as  possible. 

Calculation. — Multiply 'the  number  of  cubic  centimeters  of  permanganate  used 
by  its  copper  equivalent  as  determined  by  standardization,  and  from  the  table 
(page  546-547)  obtain  the  corresponding  value  for  the  sugar  under  examination. 

Interpretation. — See  page  539. 

8.  Fermentation  Method. — Principle. — This  method  consists  in 
the  measurement  of  the  volume  of  carbon  dioxide  evolved  when  the 
dextrose  of  the  urine  undergoes  fermentation  with  yeast.  None  of 
the  various  methods  whose  manipulation  is  based  upon  this  principle 
is  absolutely  accurate.  The  method  in  which  Einhorn's  saccharometer 
(Fig.  5,  page  30)  is  the  apparatus  employed  is  perhaps  as  satisfactory 
as  any  for  clinical  purposes. 

Procedure. — Place  about  15  c.c.  of  urine  in  a  mortar,  add  about  i  gram  of 
yeast  (1/16  of  the  ordinary  cake  of  compressed  yeast)  and  carefully  crush  the 
latter  by  means  of  a  pestle.  Transfer  the  mixture  to  the  saccharometer,  being 
careful  to  note  that  the  graduated  tube  is  completely  filled  and  that  no  air  bubbles 
gather  at  the  top.  Allow  the  apparatus  to  stand  in  a  warm  place  (3O°C.)  for  12 
hours  and  observe  the  percentage  of  dextrose  as  indicated  by  the  graduated  scale 
of  the  instrument.  Both  the  percentage  of  dextrose  and  the  number  of  cubic 
centimeters  of  carbon  dioxide  are  indicated  by  the  graduations  on  the  side  of  the 
saccharometer  tube. 

The  fermentation  method  becomes  a  much  more  accurate  procedure 
if  the  saccharometer  of  Lohnstein  is  used.2 

1  (a)  Copper  Sulphate  Solution. — Forty  grams  of  pure  crystallized  copper  sulphate  are 
dissolved  in  water  to  make  a  liter.  :¥.    . 

(b)  Alkaline  Tartrate  Solution. — Dissolve  200  grams  of  Rochelle  salts  and  150  grams  of 
NaOH  in  water  to  make  1000  c.c. 

(c)  Acid  Ferric  Sulphate  Solution. — Dissolve  50  grams  of  ferric  sulphate  in  about  200  c.c. 
of  water  and  pour  into  this  a  mixture  of  200  c.c.  of  concentrated  sulphuric  acid  diluted 
with  about  400  c.c.  of  water.     Mix  and  make  up  to  1000  c.c. 

(d)  Potassium  Permanganate  Solution. — Dissolve  5  grams  of  potassium  permanganate  in 
water  to  make  1000  c.c.    Standardization. — Dissolve  0.250  gram  of  ammonium  oxalate  in 
50-100  c.c.  of  water,  add  1-2  c.c.  of  concentrated  sulphuric  acid  and  titrate  with  the  per- 
manganate to  a  rose  color.    About  22  c.c.  will  be  required.    Multiply  the  number  of 
grams  of  oxalate  used  by  0.895  to  Set  the  equivalent  in  Cu  of  the  number  of  cubic  centi- 
meters of  permanganate  u'setfT    Calculate  the  Cu  value  of  i  c.c. 

2  Lohnstein:  Munch,  med.  Woch.,  1899,  1671. 


URINE  549 

The  availability  of  the  fermentation  procedure  as  a  quantitative 
aid  has  been  appreciably  lowered  through  the  important  findings  of 
Neuberg  and  Associates.1  They  show  that  yeast  has  the  property  of 
splitting  off  carbon  dioxide  from  the  carboxyl  group  of  amino-  and  other 
aliphatic  acids.  The  active  agent  in  this  "sugar-free  fermentation"  is 
an  enzyme  called  carboxylase.  Inasmuch  as  amino-acids  are  always 
present  in  the  urine,  the  error  from  this  source  is  apparent. 

9.  Polariscopic  Examination. — Before  subjecting  urine  to  a  polariscopic  ex- 
amination the  slightly  acid  fluid  should  be  decolorized  as  thoroughly  as  possible 
by  the  addition  of  a  little  basic  lead  acetate.    The  urine  should  be  well  stirred 
and  then  filtered  through  a  filter  paper  which  has  not  been  previously  moistened. 
In  this  way  a  perfectly  clear  and  almost  colorless  liquid  is  obtained. 

In  determining  dextrose  by  means  of  the  polariscope  it  should  be  borne  hi 
mind  that  this  carbohydrate  is  often  accompanied  by  other  optically  active  sub- 
stances, such  as  proteins,  fructose,  /3-hydroxybutyric  acid,  and  conjugate  gly- 
curonates  which  may  introduce  an  error  into  the  polariscopic  reading ;  the  method 
is,  however,  sufficiently  accurate  for  practical  purposes. 

For  directions  as  to  the  manipulation  of  the  polariscope  see  page  31. 

Below  are  given  the  specific  rotations  of  some  physiologically  important  sugars 
as  well  as  of  certain  other  optically  active  substances  the  possible  presence  of 
which  must  be  borne  in  mind  hi  determining  glucose  polarimetrically  in  urine. 

Specific  Rotation  Specific  Rotation 

Glucose  +52.49  Fructose  —92.25 

Maltose  +136.5  /3-Hydroxybutyric  —24.12 

Isomaltose  +68.0  acid. 

Lactose       t  +52.53  Conjugated  Gly-  Levorotatory     in 

Pentose  (i-ara-  o.o  curonic  Acids.  varying  degrees, 

binose). 

10.  Benedict's  Method  for  Sugar  in  Normal  Urine.2 — Principle. — The  red  color 
obtained  by  heating  a  glucose  solution  with  picric  acid  and  sodium  carbonate  is 
employed  as  the  basis  of  the  colorimetric  determination.     Acetone  is  used  to 
eliminate  color  due  to  creatinine. 

Procedure. — To  12-15  c.c.  of  urine  (sp.  gr.  not  over  1.030)  in  a  large  test  tube 
or  small  Erlenmeyer  flask  add  about  i  gm.  of  special  bone  black3  shake  1-2  minutes, 
let  stand  10  minutes,  and  filter  through  a  small  dry  filter  paper. 

From  i  to  3  c.c.  of  the  filtrate  (if  less  than  3  c.c.  are  used,  make  up  with  dis- 
tilled water  to  3  c.c.)  are  measured  into  a  graduated  test  tube  (the  tube  employed 
for  the  blood  sugar  estimation  is  satisfactory,  see  p.  287)  and  i  c.c.  of  half  saturated 
picric  acid  and  0.5  c.c.  of  5  per  cent  sodium  hydroxide  added. 

1  Neuberg  and  Associates:  Biochem.  Zeitschr.,  vol.  31  and  36,  1911. 

2  Private  communication  from  the  author. 

3  The  special  bone  black  may  be  prepared  by  treating  250  gm.  of  bone  black  with  1.5 
liters  of  dilute  hydrochloric  acid  (i  part  of  acid  to  5  parts  of  water)  and  boiling  for  30 
minutes.     The  bone  black  is  now  filtered  on  a  large  Buchner  funnel  and  washed  with 
hot  water  until  the  nitrate  is  free  from  acid. 


550  PHYSIOLOGICAL   CHEMISTRY 

When  the  tube  is  ready  to  be  put  in  the  boiling  water  bath,  5  drops  of  acetone 
solution1  are  added,  care  being  taken  that  the  acetone  does  not  fall  on  the  inside  wall 
of  the  test  tube.  The  solution  is  now  well  mixed,  the  tube  closed  with  a  cotton 
plug  and  boiled  for  15  minutes.  At  the  same  time  3  c.c.  of  a  solution  containing 
i  mg.  of  pure  glucose  are  treated  in  a  similar  sugar  tube  with  i  c.c.  of  half  saturated 
picric  acid,  0.5  c.c.  of  5  per  cent  sodium  hydroxide,  5  drops  of  the  acetone  solution 
and  then  heated  in  the  boiling  water  bath  for  the  same  length  of  time  as  the  un- 
known. 

Both  tubes  are  now  cooled  to  room  temperature,  the  standard  made  up  to  20  c.c. 
and  the  unknown  to  10,  15,  or  20  c.c.,  according  to  the  depth  of  color. 

Calculation.  —  For  the  calculation  the  following  formula  may  be  used: 

IT  X  —  X  o.ooi  X  ~  X  100  =  per  cent  of  sugar  in  urine,  in  which  R  represents 

the  reading  of  the  unknown,  D  the  dilution  of  the  unknown,  o.ooi  the  strength  of 
the  standard,  V  the  volume  of  urine  employed  and  100  the  factor  to  convert  the 
figure  to  per  cent. 

For  example,  with  a  reading  of  15,  a  dilution  of  15  and  i  c.c.  of  urine  employed, 

the  formula  would  work  out:  —  X        X  o.ooi  X  -  X  100  =  0.225  per  cent  of 

sugar  in  urine.* 

Interpretation.  —  The  quantity  of  sugar  in  normal  urine  varies  with  the  individual 
but  is  very  small  in  any  case.  The  maximum  excretion  is  probably  about  1.5  gram 
per  day. 

Protein 

i.  Scherer's  Coagulation  Method.  —  The  content  of  coagulable  protein  may 
be  accurately  determined  as  follows  :  Place  50  c.c.  of  urine  in  a  small  beaker 
and  raise  the  temperature  of  the  fluid  to  about  40  °C.  upon  a  water-bath.  Add 
dilute  acetic  acid,  drop  by  drop,  to  the  warm  urine,  to  precipitate  the  protein  which 
will  separate  hi  a  flocculent  form.  Care  should  be  taken  not  to  add  too  much 
acid  ;  ordinarily  less  than  20  drops  is  sufficient.  The  temperature  of  the  water  hi 
the  water-bath  should  now  be  raised  to  the  boiling-point  and  maintained  there 
for  a  few  minutes  hi  order  to  insure  the  complete  coagulation  of  the  protein  pres- 
ent. Now  filter  the  urine2  through  a  previously  washed,  dried,  and  weighed 
filter  paper,  wash  the  precipitated  protein,  in  turn,  with  hot  water,  95  per  cent 
alcohol,  and  with  ether,  and  dry  the  paper  and  precipitate,  to  constant  weight,  in 
an  air-bath  at  no°C.  Subtract  the  weight  of  the  filter  paper  from  the  combined 
weight  of  the  paper  and  precipitate  and  calculate  the  percentage  of  protein  in  the 
urine  specimen. 

Calculation.  —  To  determine  the  percentage  of  protein  present  in  the  urine 
under  examination,  multiply  the  weight  of  the  precipitate,  expressed  in  grams, 
by  2. 


acetone  solution  is  prepared  by  mixing  i  part  of  C.P.  acetone  with  i  part  of  dis- 
tilled water.     The  solution  should  be  freshly  prepared  at  frequent  intervals. 

2  If  it  is  desired  the  precipitate  may  be  filtered  off  on  an  unweighed  paper,  and  its 
nitrogen  content  determined  by  the  Kjeldahl  method  (see  p.  504).  In  order  to  arrive  at 
correct  figures  for  the  protein  content  it  is  then  simply  necessary  to  multiply  the  total 
nitrogen  content  by  6.25  (see  p.  345).  Correction  should  be  made  for  the  nitrogen  content 
of  the  filter  paper  used  unless  this  factor  is  negligible. 


URINE 


551 


Interpretation. — The  amount  of  albumin  occurring  in  the  urine  is 
not  necessarily  an  index  of  the  severity  or  type  of  the  disorder  giving 
rise  to  it.  Hence  no  significant  figures  can  be  given.  Normal  human 
urine  probably  contains  a  trace  of  albumin  which  is  too  slight  to  be 
detected  or  determined  by  the  usual  procedures.  The  determination 
of  albumin  may  be  of  assistance  in  following  the 
course  of  kidney  disturbances,  but  the  results  can  be 
interpreted  only  in  the  light  of  other  clinical  findings. 

2.  Esbach's  Method. — This  method  depends  upon  the  pre- 
cipitation of  protein  by  Esbach's  reagent1  and  the  apparatus 
used  in  the  estimation  is  Esbach's  albuminometer  (Fig.  169). 
In  making  a  determination  fill  the  albuminometer  to  the  point 
U  with  urine,  then  introduce  the  reagent  until  the  point  R  is 
reached.    Now  stopper  the  tube,  invert  it  slowly  several  times 
in  order  to  insure  the  thorough  mixing  of  the  fluids,  and  stand 
the  tube  aside  for  24  hours.    Creatinine,  resin, „ acids,  etc., 
are  precipitated  in  this  method,  and  for  this  and  other  reasons 
it  is  not  as  accurate  as  the  coagulation  method.    It  is,  however, 
extensively  used  clinically.    According  to  Sahli2  the  method 
is  "accurate  approximately  to  one  part  per  1000,"  whereas 
Pfeiffer3  claims  it  is  not  accurate  for  less  than  one-half  or  for 
more  than  five  parts  per  1000. 

Calculation. — The  graduations  on  the  albuminometer  indi- 
cate grams  of  protein  per  liter  of  urine.  Thus,  if  the  protein 
precipitate  is  level  with  the  figure  3  of  the  graduated  scale,  this 
denotes  that  the  urine  examined  contains  3  grams  of  protein  to 
the  liter.  To  express  the  amount  of  protein  in  per  cent  simply 
move  the  decimal  point  one  place  to  the  left.  In  the  case  under 
consideration  the  urine  contains  0.3  per  cent  protein. 

Interpretation. — See  above. 

3.  KwilecM's  Modification  of  Esbach's  Method.4 — Add  10 
drops  of  a  10  per  cent  solution  of  FeCl3  to  the  acid  urine  before 
introducing  the  Esbach's  reagent.     Warm  the  tube  and  con-     FIG.     .169.— 
tents  in  a  water-bath  at  72 °C.  for  5-6  minutes  and  make  the  ESBACH'S  ALBU^ 
reading.  MINOMETER. 

4.  Turbidity  Method  of  Folin  and  "Denis.5— Principle. — The  albumin  of  the 
urine  is  precipitated  with  sulphosalicylic  acid  and  the  turbidity  produced  com- 
pared with  that  of  a  standard  protein  solution. 

Procedure. — To  about  75  c.c.  of  water  in  each  of  two  100  c.c.  volumetric  flasks 
is  added  5  c.c.  of  a  25  per  cent  solution  of  sulphosalicylic  acid.  To  one  flask  is  then 
added  5  c.c.  of  the  standard  protein  solution  containing  10  mg.  of  albumin  and  to 

1  Esbach's  reagent  is  prepared  by  dissolving  10  grams  of  picric  acid  and  20  grams  of 
citric  acid  in  i  liter  of  water. 

2  Sahli:  Lehrbuch  d.  klin.  Untersuchungs-Methoden,  5th  Aufl.,  1909. 

3  Pfeiffer:  Berl.  klin.  Woch.,  49,  114,  1912. 


4  Kwilecki:  Munch,  med.  Woch.,  56,  p.  1330. 

5  Folin  and  Denis:  Jour.  Biol.  them.,  18,  273, 


1914. 


552  PHYSIOLOGICAL   CHEMISTRY 

the  other  is  added  the  albuminous  urine  i  c.c.  at  a  time  (by  means  of  an  Ostwald 
pipette)  until  the  turbidity  obtained  seems  to  be  reasonably  near  that  of  the 
standard.  The  two  flasks  are  then  filled  up  to  the  mark  with  water,  cautiously 
inverted  a  few  times  to  secure  mixing,  and  are  then  ready  for  the  quantitative 
comparison  just  as  in  colorimetric  work.  The  standard  must  invariably  be  read 
against  itself.  The  standard1  containing  10  mg.  of  protein  is  set  at  20  mm.  The 
unknown  must  not  read  less  than  10  nor  more  than  30. 

Calculation. — Dividing  200  by  the  product  of  the  reading  of  the  unknown  and 
the  number  of  cubic  centimeters  of  urine  taken  gives  the  albumin  in  milligrams  per 
cubic  centimeter  of  urine.  The  albuminous  suspensions  must  not  be  shaken  but 
mixed  very  carefully.  The  method  is  fairly  accurate  and  requires  but  a  few  minutes 
if  a  standard  solution  is  at  hand.  The  method  is  not  applicable  to  urines  deeply 
colored  with  blood  or  bile  but  may  be  used  for  albuminous  fluids  other  than  urine 
if  such  fluids  are  not  highly  pigmented.  It  must  be  borne  in  mind  that  different 
proteins,  as  serum  albumin  and  serum  globulin,  may  give  markedly  different  degrees 
of  turbidity  under  the  same  conditions.2 

Interpretation. — See  page  551. 

Bence-Jones  Protein.  Method  of  Folin  and  Denis.3 — Principle. — A  known 
volume  of  urine  is  heated  at  6o°?  the  coagulated  Bence-Jones  protein  is  then 
thrown  down  by  centrifugation,  washed  with  50  per  cent,  alcohol,  dried  and 
weighed. 

Procedure. — Place  10  c.c.  of  the  urine  containing  Bence-Jones  protein  in  a  pre- 
viously weighed,  conical  centrifuge  tube,  add  i  c.c.  of  5  per  cent,  acetic  acid,4 
and  allow  to  stand  overnight6  in  a  water  bath  at  60° C.  The  next  morning  remove 
the  tube  from  the  bath,  centrifuge  for  a  few  minutes  and  pour  off  the  supernatant 
liquid.  Stir  the  sediment  well  with  about  10  c.c.  of  50  per  cent,  alcohol,  centrifuge, 
pour  off  the  a  cohol,  dry  at  ioo°C.  to  constant  weight,  cool,  and  weigh. 

Calculation. — Subtract  the  weight  of  the  empty  tube  from  that  of  the  tube  and 
protein  to  obtain  the  weight  of  Bence-Jones  protein  contained  in  10  c.c.  of  urine. 
Calculate,  from  this  figure,  the  percentage  and  24-hour  output. 

Interpretation. — For  a  discussion  of  the  significance  of  Bence-Jones  proteinuria 
see  p.  442. 

Acetone  Bodies 

Van  Slyke's  Methods.6— Principle. — The  method  is  based  on  a  com- 
bination of  Shaffer's  oxidation  of  /Miydroxybutyric  acid  to  acetone, 
and  Denige's  precipitation  of  acetone  as  a  basic  mercuric  sulphate 

1  Standard   Albumin  solution.    Fresh  blood  serum  free  from  hemoglobin  is  used. 
25-35  c.c.  of  the  serum  are  diluted  with  a  15  per  cent  solution  of  chemically  pure  sodium 
chloride  to  about  1500  c.c.    The  solution  is  mixed  and  filtered.     By  means  of  nitrogen 
determinations  the  protein  content  of  the  filtrate  is  determined  (protein  =  NX  6.25)  and 
on  the  basis  of  the  figure  obtained  the  solution  is  diluted  with  15  per  cent  sodium  chloride 
solution  so  that  it  contains  2  mg.  of  protein  per  cubic  centimeter.     It  is  best  to  saturate 
the  albumin  solution  with  chloroform.     The  solution  keeps  for  months. 

2  Marshall  and  Banks:  Proceedings  of  the  American  Philosophical  Society,  54,  176, 
iQiS. 

a  Folin  and  Denis:  Jour.  Biol.  Chem.,  18,  277,  1914. 

4  Taylor  and  Miller  (Jour.  Biol.  Chem.,  25,  281,  1916)  suggest  the  use  of  only  a  trace  of 
acetic  acid. 

6  From  6  P.  M.  until  8  A.  M.  is  suggested  as  convenient. 
•Van  Slyke : /owr.  Biol.  Chem.,  32,  455,  1917. 


URINE  553 

compound.  Glucose  and  certain  other  interfering  substances  are  re- 
moved by  precipitation  with  copper  sulphate  and  calcium  hydroxide. 
Preservatives  other  than  toluene  or  copper  sulphate  should  not  be  used. 

Procedure. — Removal  of  Glucose  and  other  Interfering  Substances  from 
Urine. 

Place  25  c.c.  of  urine  in  a  250  c.c.  measuring  flask.  Add  100  c.c.  of  water, 
50  c.c.  of  copper  sulphate  solution l  and  mix.  Then  add  50  c.c.  of  10  per  cent 
calcium  hydroxide  suspension,  shake,  and  test  with  litmus.  If  not  alkaline,  add 
-nore  calcium  hydroxide.  Dilute  to  the  mark  and  let  stand  at  least  one-half 
hour  for  glucose  to  precipitate.  Filter  through  a  dry  folded  filter.  This  procedure 
will  remove  up  to  8  per  cent  of  glucose.  Urine  containing  more  should  be  diluted 
enough  to  bring  the  glucose  down  to  8  per  cent.  The  copper  treatment  is  de- 
pended upon  to  remove  interfering  substances  other  than  glucose,  and  should 
therefore  never  be  omitted,  even  when  glucose  is  absent.  The  filtrate  may  be 
tested  for  glucose  by  boiling  a  little  in  a  test-tube.  A  precipitate  of  yellow 
cuprous  oxide  will  be  obtained  if  the  removal  has  not  been  complete.  A  slight 
precipitate  of  white  calcium  salts  always  forms,  buJt  does  not  interfere  with  the 
detection  of  the  yellow  cuprous  oxide. 

Determination  of  Total  Acetone  Bodies  (Acetone,  Acetoacetic  Acid,  and 
/3-hydroxybutyric  Acid.) — Place  in  a  500  c.c.  Erlenmeyer  flask  25  c.c.  of  urine 
filtrate.  Add  100  c.c.  of  water,  10  c.c.  of  50  per  cent  sulphuric  acid,  and  35 
c.c.  of  the  10  per  cent  mercuric  sulphate.  Or  hi  place  of  adding  the  water  and 
reagents  separately,  add  145  c.c.  of  the  "combined  reagents."  Connect  the  flask 
with  a  reflux  condenser  having  a  straight  condensing  tube  of  8  or  10  mm.  dia- 
meter and  heat  to  boiling.  After  boiling  has  begun,  add  5  c.c.  of  the  5  per  cent 
dichromate  through  the  condenser  tube.  Continue  boiling  gently  11/2  hours. 
The  yellow  precipitate  which  forms  consists  of  the  mercury  sulphate-chromate 
compound2  of  the  preformed  acetone,  and  the  acetone  which  has  been  formed 
by  decomposition  of  acetoacetic  acid  and  by  oxidation  of  the  0-hydroxybutyric 
acid.  It  is  collected  in  a  Gooch  or  "medium  density"  alundum  crucible,  washed 
with  200*  c.c.  of  cold  water,  and  dried  for  an  hour  at  110°.  The  crucible  is 
allowed  to  cool  in  room  ah*  (a  desiccator  is  unnecessary  and  undesirable)  and 
weighed.  Several  precipitates  may  be  collected,  one  above  the  other,  without 
cleaning  the  crucible.  As  an  alternative  to  weighing,  the  precipitate  may  be  dis- 
solved and  titrated  as  described  below. 

Determination  of  Acetone  and  Acetoacetic  Acid. — The  acetone  plus  the 
acetoacetic  acid,  which  completely  decomposes  into  acetone  and  CO  2  on  heat- 

1  Solutions  Required. — 20  per  cent  copper  sulphate — 200  grams  of  CuSO^sHjO  dissolved 
in  water  and  made  up  to  i  liter. 

10  per  cent  mercuric  sulphate — 73  grams  of  pure  red  mercuric  oxide  dissolved  in  i 
liter  of  H2SO4  of  4  N.  concentration. 

50  volume  per  cent  sulphuric  acid — 500  c.c.  of  sulphuric  acid  of  1.83 5  specific  gravity, 
diluted  to  i  liter  with  water.  Concentration  of  H2SO4  must  be  readjusted  if  necessary 
to  make  it  17.0  N  by  titration. 

10  per  cent  calcium  hydroxide  suspension — mix  100  grams  of  Merck's  fine  light  "rea- 
gent" Ca(OH)2  with  i  liter  of  water. 

5  per  cent  potassium  dichromate — 50  grams  K2Cr2O7  dissolved  in  water  and  made 
up  to  i  liter. 

Combined  reagents  for  total  acetone  body  determination— i  liter  of  the  above  50 
per  cent  sulphuric  acid,  3.5  liters  of  the  mercuric  sulphate,  10  liters  of  water. 

*This  contains  about  77  per  cent  mercury  and  in  the  absence  of  chromate  has  approximately 
one  of  the  following  formulas:  3HgSO4.5HgO.2(CH,)2  CO  or 


554  PHYSIOLOGICAL   CHEMISTRY 

ing,  is  determined  without  the  /3-hydroxybutyric  acid  exactly  as  the  total 
acetone  bodies,  except  that  (i)  no  dichromate  is  added  to  oxidize  the  0-hydroxy- 
butyric  acid  and  (2}  the  boiling  must  continue  for  not  less  than  30  nor  more  than 
45  minutes.  Boiling  for  more  than  45  minutes  splits  off  a  little  acetone  from 
/3-hydroxybutyric  acid  even  in  the  absence  of  chromic  acid.1 

Determination  of  /3-hydroxybutyric  Acid. — The  /3-hydroxybutyric  acid  alone 
is  determined  exactly  as  total  acetone  bodies  except  that  the  preformed 
acetone  and  that  from  the  acetoacetic  acid  are  first  boiled  off.  To  do  this  the 
25  c.c.  of  urine  filtrate  plus  100  c.c.  of  water  are  treated  with  2  c.c.  of  the  50  per 
cent  sulphuric  acid  and  boiled  in  the  open  flask  for  10  minutes.  The  volume  of 
solution  left  hi  the  flask  is  measured  in  a  cylinder.  The  solution  is  returned  to 
the  flask,  and  the  cylinder  washed  with  enough  water  to  replace  that  boiled  off 
and  restore  the  volume  of  the  solution  to  127  c.c.  Then  8  c.c.  of  the  50  per 
cent  sulphuric  acid  and  35  c.c.  of  mercuric  sulphate  are  added.  The  flask  is 
connected  under  the  condenser  and  the  determination  is  continued  as 
described  for  total  acetone  bodies. 

Titration  of  the  Precipitate  hi  the  Above  Methods. — Instead  of  weighing  the 
precipitate,  one  may  wash  the  contents  of  the  Gooch,  including  the  asbestos, 
into  a  small  beaker  with  as  little  water  as  possible,  and  add  15  c.c.  of 
normal  HC1.  The  mixture  is  then  heated,  and  the  precipitate  quickly  dissolves. 
In  case  an  alundum  crucible  is  used,  it  is  set  into  the  beaker  of  acid  until  the 
precipitate  dissolves,  and  then  washed  with  suction,  the  washings  being  added 
to  the  beaker.  In  place  of  using  either  a  Gooch  or  alundum  crucible  one  may, 
when  titration  is  employed,  wash  the  precipitate  without  suction  on  a  small 
quantitative  filter  paper,  which  is  transferred  with  the  precipitate  to  the  beaker 
and  broken  up  with  a  rod  in  15  c.c.  of  normal  HC1. 

In  order  to  obtain  a  good  end-point  hi  the  subsequent  titration  it  is  necessary 
to  reduce  the  acidity  of  the  solution.  For  this  purpose  it  has  been  found  that  the 
addition  of  excess  sodium  acetate  is  the  most  satisfactory  means.  Six  to  7  c.c. 
of  3  M  acetate  are  added  to  the  cooled  solution  of  redissolved  precipitate.  Then 
the  0.2  M  KI  is  run  hi  rapidly  from  a  burette  with  constant  stirring.  If  more  than 
a  small  amount  of  mercury  is  present,  a  red  precipitate  of  HgI2  at  once  forms,  and 
redissolves  as  soon  as  2  or  3  c.c.  of  KI  hi  excess  of  the  amount  required  to  form 
the  soluble  K<>Hgl4  have  been  added.  If  only  a  few  mg.  of  mercury  are  present, 
the  excess  of  KI  may  be  added  before  the  HgI2  has  had  tune  to  precipitate  so 
that  the  titrated  solution  remains  clear.  In  this  case  not  less  than  5  c.c.  of  the 
0.2  M  KI  are  added,  as  it  has  been  found  that  the  final  titration  is  not  satisfac- 
tory if  less  is  present.  The  excess  of  KI  is  titrated  back  by  adding  0.05  M 
HgCl2  from  another  burette  until  a  permanent  red  precipitate  forms.  Since 

1  Blank  Determination  of  Precipitate  from  Substances  in  Urine  Other  than  the  Acetone  Bodies, 
— The  25  c.c  aliquot  of  urine  filtrate  is  treated  with  sulphuric  acid  and  water  and  boiled 
10  minutes  to  drive  off  acetone.  The  residue  is  made  up  to  175  c.c.  with  the  same  amounts 
of  mercuric  sulphate  and  sulphuric  acid  used  in  the  above  determinations,  but  without 
chromate,  and  is  boiled  under  the  reflux  for  45  minutes.  Longer  boiling  splits  off  some 
acetone  from  /3-hydroxybutyric  acid,  and  must  therefore  be  avoided.  The  weight  of 
precipitate  obtained  may  be  subtracted  from  that  obtained  in  the  above  determination. 
The  blank  is  so  smaU  that  it  appears  to  be  relatively  significant  only  when  compared 
with  the  small  amounts  of  acetone  bodies  found  in  normal  or  nearly  normal  urines.  In 
routine  analyses  of  diabetic  urines  it  is  not  determined. 

Tests  of  Reagents. — When  the  complete  total  acetone  bodies  determination,  including 
the> 'preliminary  copper  sulphate  treatment,  is  performed  on  a  sample  of  distilled  water 
instead  of  urine  no  precipitate  whatever  should  be  obtained.  This  test  must  not  be 
omitted. 


URINE  .       555 

the  reaction  utilized  is  HgCl2  +  4KI  =  K2HgI4  +  KC1,  i  c.c.  of  0.05  M 
HgCl2  is  equivalent  in  the  titration  to  i  c.c.  of  the  0.2  M  KI. 

In  preparing  the  two  standard  solutions  the  0.05  M  HgCl2  is  standardized  by 
the  sulphide  method,  and  the  iodine  is  standardized  by  titration  against  it. 
A  slight  error  appears  to  be  introduced  if  the  iodide  solution  is  gravimetrically 
standardized  and  used  for  checking  the  mercury  solution,  instead  of  vice  versa. 

In  standardizing  the  mercuric  chloride  the  following  procedure  has  been 
found  convenient :  25  c.c.  of  0.05  M  HgCl2  are  measured  with  a  calibrated  pi- 
pette, diluted  to  about  100  c.c.,  and  H2S  is  run  in  until  the  black  precipitate  floc- 
culates and  leaves  a  clear  solution.  The  HgS,  collected  in  a  Gooch  crucible 
and  dried  at  no0,  should  weigh  0.2908  gram  if  the  solution  is  accurate. 

Both  by  gravimetric  analyses  of  the  basic  mercuric  sulphate -acetone  pre- 
cipitate and  by  titration,  the  mercury  content  of  the  precipitate  has  been  found 
to  average  76.9  per  cent.  On  this  basis,  each  c.c.  of  0.2  M  KI  solution,  being 
equivalent  to  10.0  mg.  of  Hg,  is  equivalent  to  13.0  mg.  of  the  mercury  acetone 
precipitate. 

Titration  is  not  quite  so  accurate  as  weighing,  but,  except  when  the  amounts 
determined  are  very  small,  the  titration  is  satisfactory. 

Calculation. — i  mg.  of  j3-hydroxybutyric  acid  yields  8.45  mg.  of  precipitate, 
i  mg.  of  acetone  yields  20.0  mg.  of  precipitate,  i  c.c.  of  0.2  M  KI  solution 
is  equivalent  to  13  mg.  of  precipitate  hi  titration  of  the  latter. 

In  order  to  calculate  the  acetone  bodies  as  /3-hydroxybutyric  acid  rather 
than  acetone,  use  the  above  factors  multiplied  by  the  ratio  of  the  molecular 

/3-acid       104 
weights   j — i =  -— g-  =  1.793.    la    order    to    calculate  the  acetone  bodies 

in  terms  of  molecular  concentration,  divide  the  factors  in  the  table  by  58.  To 
calculate  c.c.  of  o.i  M  acetone  bodies  per  liter  of  urine  use  the  above  factors 

,  .  i-  j.     10,000 

multiplied  by =--  =  172.4. 

5o 

Special  Factors  for  Calculation  of  Results  when  25  c.c.  of  Urine  Filtrate, 
Equivalent  to  2.5  c.c.  of  Urine,  are  used  for  the  Determination. 

Acetone  bodies,  calculated  as  gm. 


ueienmnauon  penormea 

acetone  per  liter  01  urine,  indi- 
cated by 

i  gm.  of  prec. 

I  C.C.  Of  0.2  M  KI  SOl. 

Total  acetone  bodies1    • 

24.8 
26.4 

20.0 

0.322 

0.344 

0.260 

/3-Hydroxybutyric  acid 

Acetone2  +  acetoacetic  acid 

1  The  "total  acetone  bodies"  factor  is  calculated  on  the  assumption  that  the  molecular 
proportion  of  them  in  the  form  /8-hydroxybutyric  acid  is  75  per  cent  of  the  total,  which 
proportion  is  usually  approximated  in  acetonuria.     Because  /3-hydroxybutyric  acid  yields 
only  0.75  molecule  of  acetone,  the  factors  are  strictly  accurate  only  when  this  proportion 
is  present,  but  the  error  introduced  by  the  use  of  the  approximate  factors  is  for  ordinary 
purposes  not  serious.    The  actual  errors  in  percentage  of  the  amounts  determined  are  as 
follows:  molecular  proportion  of  acetone  bodies  as  /3-acid  0.50,  error  6.5  per  cent;  /3-acid 
60.0,  error  3.8  per  cent;  /3-acid  0.80,  error  1.3  per  cent. 

2  For  the  determination  of  preformed  acetone  see  method  p.  557. 


556  PHYSIOLOGICAL   CHEMISTRY 

Interpretation. — Normal  adults  on  a  mixed  diet  excrete  on  the 
average  3-15  mg.  of  combined  acetone  and  acetoacetic  acid  per  day 
and  anything  over  20  mg.  is  usually  pathological.  Usually  about  one- 
fourth  of  this  total  is  acetone  although  the  proportion  varies  consid- 
erably. The  amount  is  considerably  increased  in  pasting  and  on  a 
carbohydrate-free  diet  due  to  the  development  of  acidosis.  In  severe 
diabetic  acidosis  values  up  to  6  grams  per  day  or  even  higher  may  be 
noted.  It  is  sometimes  found  in  large  amounts  in  intoxications  asso- 
ciated with  pregnancy.  It  may  be  found  in  increased  amounts  in  the 
urine  in  a  great  variety  of  pathological  conditions.  Quantative  estima- 
tion enables  us  to  follow  the  course  of  the  acidosis.  Ammonia  excre- 
tion is  also  largely  increased  in  these  conditions,  being  used  in  the 
neutralization  of  the  excess  acids  formed  in  the  body.  Usually  about 
three-quarters  of  the  combined  acetone  and  acetoacetic  acid  excretion 
is  in  the  form  of  acetoacetic  acid,  but  the  proportion  is  not  constant. 

j8-hydroxybutyric  acid  may  occur  in  normal  human  urine  to  the 
extent  of  20-30  mg.  per  day.  In  fasting  or  on  a  carbohydrate-free 
diet  very  large  amounts  may  be  excreted  (up  to  20  grams  per  day). 
In  severe  diabetes  mellitus  the  largest  amounts  are  found,  and  excre- 
tions of  50  or  even  100  grams  or  over  per  day  have  been  noted.  In 
this  condition  it  is  usually  the  most  abundant  of  the  acetone  bodies 
making  up  from  60-80  per  cent  of  the  total.  The  ratio  is,  however, 
by  no  means  constant  and  it  should  be  borne  in  mind  that  in  rare  cases 
large  amounts  of  0-hydroxybutyric  acid  may  be  eliminated  although 
the  acetone  excretion  is  very  low.  It  is  always  present  in  the  urine 
when  large  amounts  of  acetone  are  present. 

Acidosis  is  due  mainly  to  a  disturbance  in  the  metabolism  of  fats. 
The  fatty  acids  are  ordinarily  oxidized  to  acetoacetic  acid,  which  is 
either  oxidized  through  formic  and  acetic  acids  to  carbon  dioxide 
and  water,  or  by  reduction  forms  j8-hydroxy butyric  acid.  When  fat 
catabolism  is  increased  to  such  an  extent  that  the  body  cannot  bring 
about  complete  oxidation  of  the  products  formed,  a  considerable  por 
tion  of  the  acetoacetic  acid  instead  of  being  oxidized  in  this  way  is 
transformed  into  acetone  and  in  more  severe  cases  into  /3-hydroxybuty- 
ric  acid  which  will  then  be  eliminated  to  varying  degrees  in  the  urine. 

The  relation  of  the  acetone  bodies  is  indicated  in  the  following 
scheme. 

...  »  loss  of  CO2 

CH3-CO.CH2-COOH    >     CH3.CO.CH3 

(Acetoacetic  acid.)  (Acetone.) 

*      by  reduction 

CH3  -  CHOH  -  CH2  -  COOH 

(/3-hydr  xybutyric  acid) 


URINE  557 

In  fasting  the  decomposition  of  fat  is  increased  due  to  the  lack 
of  carbohydrate  material  and  acidosis  develops.  The  same  holds  true 
for  a  carbohydrate-free  diet.  Apparently,  also,  fat  is  much  less 
readily  oxidized  in  the  presence  of  a  carbohydrate  deficiency. 

Acetone 

Folin's  Method. — Principle. — The  preformed  acetone  is  aspirated 
from  the  urine  mixture  at  room  temperature  to  prevent  decompo- 
sition of  acetoacetic  acid.  The  acetone  is  collected  in  alkaline 
hypoiodite  solution  as  in  the  Folin-Hart  method.  lodoform  is  formed 
quantitatively  and  the  excess  of  iodine  is  titrated  with  sodium  thio- 
sulphate. 

Procedure. — The  same  type  of  apparatus  is  used  in  this  method  as  that 
described  in  Folin's  method  for  the  determination  of  ammonia  (see  page  519). 
Introduce  20-25  c.c.  of  the  urine  under  examination  into  the  aerometer  cylinder 
and  add  10  drops  of  10  per  cent  phosphoric  acid,1 8-10  grams  of  sodium  chloride. ? 
and  a  little  petroleum.  Introduce  into  an  absorption  flask,3  such  as  is  used  in  the 
ammonia  determination  (see  page  519),  150  c.c.  of  water,  10  c.c.  of  a  40  per  cent 
solution  of  potassium  hydroxide,  and  an  excess  of  a  N/io  iodine  solution.  Con- 
nect the  flask  with  the  aerometer  cylinder,  attach  a  Chapman  pump,  and  permit 
an  air  current,  slightly  less  rapid  than  that  used  for  the  determination  of  ammonia, 
to  be  drawn  through  the  solution  for  20-25  minutes.  All  of  the  acetone  will,  at 
this  point,  have  been  converted  into  iodoform  in  the  absorption  flask.  Add 
10  c.c.  of  concentrated  hydrochloric  acid  (a  volume  equivalent  to  that  of  the 
strong  alkali  originally  added),  to  the  contents  of  the  latter  and  titrate  the 
excess  of  iodine  by  means  of  N/io  sodium  thiosulphate  solution  until  a  light 
yellow  color  is  obtained.  At  this  point  add  a  few  cubic  centimeters  of  starch 
paste  and  titrate  the  mixture  until  no  blue  color  is  visible.  This  is  the  end 
reaction. 

Calculation. — Subtract  the  number  of  cubic  centimeters  of  N/io  thiosulphate 
solution  used  from  the  volume  of  N/io  iodine  solution  employed.  Since  i  c.c.  of 
the  iodine  solution  is  equivalent  to  0.967  mg.  of  acetone,  and  since  i  c.c.  of  the 
thiosulphate  solution  is  equivalent  to  i  c.c.  of  the  iodine  solution,  if  we  multiply 
the  remainder  from  the  above  subtraction  by  0.967  we  will  obtain  the  number 
of  milligrams  of  acetone  in  the  volume  of  urine  employed. 

Calculate  the  quantity  of  acetone  in  the  twenty-four-hour  urine  specimen. 

Interpretation. — See  Van  Slyke's  Methods,  page  556. 

Folin  has  further  made  suggestions  regarding  the  simultaneous  determination 
of  acetone  and  ammonia  by  the  use  of  the  same  air  current.4  This  is  an  important 

1  Oxalic  acid  (0.2—0.3  gram)  may  be  substituted  if  desired. 

*  Acetone  is  insoluble  in  a  saturated  solution  of  sodium  chloride. 

3  Folin's  improved  absorption  tube  (see  Fig.  168,  p.  520)  should  be  used  in  this  connec- 
tion inasmuch  as  the  original  type  embracing  the  use  of  a  rubber  stopper  is  unsatisfactory 
because  of  the  solvent  action  of  alkaline  hypoiodite  on  rubber. 

4  These  determinations  may  even  be  made  on  the  same  sample  of  urine  if  the  sample  is 
too  small  for  the  double  determination. 


558  PHYSIOLOGICAL   CHEMISTRY 

consideration  for  the  clinician  inasmuch  as  urines  which  contain  acetone  and  aceto- 
acetic  acid  are  generally  those  from  which  the  ammonia  data  are  also  desired.  The 
procedure  for  the  combination  method  is  as  follows:  Arrange  the  ammonia  appar- 
atus as  usual  (see  page  519),  and  to  the  aerometer  of  the  ammonia  apparatus  attach 
the  acetone  apparatus  set  up  as  described  above.  Regulate  the  air  current  with 
special  reference  to  the  determination  of  acetone  and  at  the  end  of  20-25  minutes 
disconnect  the  acetone  apparatus  and  complete  the  determination  of  the  acetone 
as  just  described.  The  air  current  is  not  interrupted,  and  after  having  run  one 
and  one-half  hours  the  ammonia  apparatus  is  detached  and  the  ammonia  determina- 
tion completed  as  described  on  page  519. 

If  data  regarding  acetoacetic  acid  are  desired,  the  result  obtained  by  Folin's 
method  may  be  subtracted  from  the  result  obtained  by  the  Van  Slyke  method 
for  acetone  and  acetoacetic  acid.  Under  all  conditions  the  determination  of 
acetone  should  be  as  expeditious  as  possible.  This  is  essential,  not  only  because 
of  the  fact  that  any  acetoacetic  acid  present  in  the  urine  will  become  transformed 
into  acetone,  but  also  because  of  the  rapid  spontaneous  decomposition  of  the  alka- 
line hypoiodite  solution  used  in  the  determination  of  the  acetone.  It  has  been 
claimed  that  alkaline  hypoiodite  solutions  are  almost  completely  converted  into 
iodate  solutions  in  one-half  hour.  Folin  states,  however,  that  the  transformation 
is  not  so  rapid  as  this,  but  he  nevertheless  emphasizes  the  necessity  of  rapidity  of 
manipulation.  At  the  same  time  it  should  be  remembered  that  the  air  current 
must  not  be  as  rapid  as  for  ammonia,  inasmuch  as  the  alkaline  hypoiodite  solution 
will  not  absorb  all  the  acetone  under  those  conditions. 

Indican 

Ellinger's  Method. — Principle. — This  method  for  the  quantitative 
determination  of  indican  is  based  upon  the  principle  underlying  Jaffe's 
qualitative  test  for  indican.  The  urine  after  removal  of  interfering 
substances  with  basic  lead  acetate  is  treated  with  Obermayer's  reagent 
to  oxidize  the  indican  to  indigo.  The  indigo  is  extracted  with  chloro- 
form, the  chloroform  evaporated  off  and  the  residue  titrated  with 
potassium  permanganate.  The  method  is  not  very  accurate  but  is  as 
satisfactory  as  any. 

Procedure. — To  50  c.c.  of  urine1  in  a  small  beaker  or  casserole  add  5  c.c. 
of  basic  lead  acetate  solution,2  mi*  thoroughly,  and  filter.  Transfer  40  c.c.  of 
the  filtrate  to  a  separatory  funnel,  add  an  equal  volume  of  Obermayer's  reagent 
(see  page  405)  and  20  c.c.  of  chloroform,  and  extract  in  the  usual  manner.  This 
extraction  with  chloroform  should  be  repeated  until  the  chloroform  solution 
remains  colorless.  Shake  up  the  combined  chloroform  extracts  two  or  three 
times  with  distilled  water  in  a  separating  funnel  and  complete  the  purification 
by  extracting  with  very  dilute  sodium  hydroxide  (i  :iooo).  Remove  all  traces 
of  alkali  by  washing  with  water.  Now  filter  the  combined  chloroform  extracts 
through  a  dry  filter  paper  into  a  dry  Erlenmeyer  flask.  Distil  off  the  chloro- 
form, heat  the  residue  on  a  boiling  water-bath  for  five  minutes  in  the  open 

1  If  the  urine  under  examination  is  neutral  or  alkaline  in  reaction  it  may  .be  made 
faintly  acid  with  acetic  acid  before  adding  the  basic  lead  acetate. 

2  For  preparation  of  basic  lead  acetate  solution  see  p.  629. 


URINE  559 

flask,  and  wash  the  dried  residue  with  hot  water.1  Add  10  c.c.  of  concentrated 
sulphuric  acid  to  the  washed  residue,  heat  on  the  water-bath  for  five  to  ten 
minutes,  dilute  with  100  c.c.  of  water,  and  titrate  the  blue  solution  with  a  very 
dilute  solution  of  potassium  permanganate.2  The  end  point  is  indicated  by  the 
dissipation  of  all  the  blue  color  from  the  solution  and  the  formation  of  a  pale 
yellow  color. 

Beautiful  plates  of  indigo  blue  sometimes  appear  in  the  chloroform  extract 
of  urines  containing  abundant  indican.  In  urines  preserved  by  thymol  the 
determination  of  indican  is  interfered  with  unless  great  care  is  taken  in  washing 
the  chloroform  extract  with  dilute  alkali.  Care  should  be  taken,  therefore,  to 
make  the  indican  determination  upon  fresh  urine,  before  the  addition  of  the 
preservative. 

Plasencia3  has  suggested  a  method  which  is  shorter  than  Ellinger's  and  ac- 
cording to  its  sponsor,  just  as  accurate. 

Calculation. — One  cubic  centimeter  of  the  diluted  permanganate  solution 
is  equivalent  to  about  0.15  mg.  of  indigo.  Ellinger  claims  that  one-sixth  of  the 
amount  determined  must  be  added  to  the  value  obtained  by  titration  in  order  to 
secure  accurate  data.  This  correction  should  always  be  made. 

Interpretation. — From  4-20  mg.  of  indican  are  excreted  per  day  by 
normal  men.  In  normal  individuals  the  variations  are  dependent 
mainly  upon  the  diet.  A  meat  diet  increases  the  indican  excretion, 
while  a  milk  or  carbohydrate-rich  diet  decreases  it.  Pathologically 
the  greatest  increases  are  found  in  disorders  involving  increased 
putrefaction  and  stagnation  of  intestinal  contents.  Bacterial  de- 
composition of  body  protein  as  in  gangrene,  putrid  pus  formation,  etc., 
gives  rise  to  increases. 

Phenols 

Colorimetric  Method  of  Folin  and  Denis.4 — Principle. — This  method 
is  based  upon  the  fact  that  phenols  yield  with  a  solution  of  phospho- 
tungstic-phosphomolybdic  acid  and  alkali  a  deep  blue  color  the  depth 
of  which  is  proportional  to  the  amount  of  such  substances  present. 
Traces  of  protein,  which  may  be  present  in  the  urine,  and  uric  acid 
give  a  blue  color  with  the  reagent  and  are  removed  by  precipitation 
with  an  acid  silver  lactate  solution  and  colloidal  iron  as  a  preliminary 
to  the  determination  of  the  phenols. 

Procedure. — Removal  of  Interfering  Substances. — Place  10  c.c.  of  ordinary 
urine,  or  20  c.c.  of  a  dilute  urine  in  a  50  c.c.  volumetric  flask.  /  To  this  add  an 

1  The  washing  should  be  continued  until  the  wash  water  is  no  longer  colored.    Ordi- 
narily two  or  three  washings  are  sufficient.    If  a  separation  of  indigo  particles  takes  place 
during  the  washing  process,  the  wash  water  should  be.  filtered,  the  indigo  extracted  with 
chloroform,  and  the  usual  method  applied  from  this  point. 

2  A  "stock  solution"  of  potassium  permanganate  containing  3  grams  per  liter  should  be 
prepared,  and  when  needed  for  titration  purposes  a  suitable  volume  of  this  solution  should 
be  diluted  with  40  volumes  of  water.    The  potassium  permanganate  solution  may  be 
standardized  with  pure  indigo. 

3  Plasencia:  Revista  de  Medicina  y  Cirugia.,  17,  i,  1912. 

4  Folin  and  Denis:  /.  Biol.  Chem.,  22,  305,  1915. 


560  PHYSIOLOGICAL   CHEMISTRY 

acid  silver  lactate  solution  (from  2  to  20  c.c.  of  a  3  per  cent  solution  of  silver 
lactate  in  3  per  cent  lactic  acid)  until  no  further  precipitate  is  obtained.  Add 
a  few  drops  of  colloidal  iron,  shake  the  flask,  dilute  to  mark  with  distilled  water, 
shake  again,  and  filter  the  contents  through  a  dry  filter.  Phenols  are  not  pre- 
cipitated by  this  procedure  but  are  recovered  quantitatively  in  the  filtrate.  Trans  - 
fer  25  c.c.  of  the  filtrate  to  a  50  c.c.  volumetric  flask,  and  add  a  sufficient  quantity 
of  saturated  sodium  chloride  solution,  containing  10  c.c.  of  strong  hydrochloric 
acid  per  liter,  to  precipitate  all  the  silver.  Fill  the  flask  to  the  mark  with  dis- 
tilled water,  mix  thoroughly,  and  filter  through  a  dry  filter.  This  filtrate,  which 
contains  half  the  phenol  from  the  urine  taken  for  analysis,  is  used  for  the  deter- 
mination of  free  and  total  phenols. 

Free  Phenols. — Place  20  c.c.  of  the  filtrate  mentioned  above  in  a  50  c.c. 
volumetric  flask,  add  5  c.c.  of  the  phosphotungstic-phosphomolybdic  acid  re- 
agent1 and  15  c.c.  of  a  saturated  solution  of  sodium  carbonate.  Dilute  to  volume 
with  luke  warm  water  (3O-35°C.),  mix  thoroughly  and  after  allowing  to  stand 
for  20  minutes  compare  the  deep  blue  color  in  the  Duboscq  colorimeter  (see 
Fig.  1 60,  page  508)  against  a  standard  solution  of  phenol  (see  below)  similarly 
treated. 

Total  Phenols  (Free  and  Conjugated). — Place  20  c.c.  of  the  same  filtrate 
used  for  the  determination  of  free  phenols  in  a  large  test-tube,  add  10  drops 
of  concentrated  hydrochloric  acid,  cover  the  tube  with  a  small  funnel,-  heat 
rapidly  to  boiling  over  a  free  flame,  and  then  place  hi  a  boiling  water-bath  for 
ten  minutes.  This  process  serves  to  decompose  the  conjugated  phenols.  At 
the  end  of  the  ten  minutes,  remove  the  tube,  cool,  and  transfer  the  contents 
to  a  100  c.c.  volumetric  flask.  Add  10  c.c.  of  the  phosphotungstic-phospho- 
molybdic  reagent,  25  c.c.  of  saturated  sodium  carbonate  solution,  dilute  to  mark 
with  luke  warm  water  (3O-35°C.),  mix  thoroughly,  allow  to  stand  for  20  minutes, 
and  read  in  the  Duboscq  colorimeter  (see  page  508)  against  a  standard  solution 
of  phenol  (see  below). 

Standard  Solution  of  Phenol. — The  standard  used  is  a  solution  of  pure  phenol 
in  N/ioo  hydrochloric  acid  containing  i  mg.  of  phenol  in  10  c.c.,  standardized  by 
means  of  the  iodometric  titration.  The  preparation  is  carried  out  as  follows:  Make 
a  phenol  solution  in  N/io  hydrochloric  acid,  which  contains  approximately  i  mg.  of 
crystallized  phenol  per  cubic  centimeter.  Transfer  25  c.c.  of  this  solution  to  a 
250  c.c.  flask,  add  50  c.c.  of  N/io  sodium  hydroxide,  heat  to  65°C.,  add  25  c.c.  of 
N/io  iodine  solution,  stopper  the  flask,  and  let  stand  at  room  temperature  30  or 
40  minutes.  Add  5  c.c.  of  concentrated  hydrochloric  acid  and  titrate  the  excess 
of  iodine  with  N/io  thiosulphate  solution.  Each  cubic  centimeter  of  N/io  iodine 
solution  corresponds  to  1.567  mg.  of  phenol.  On  the  basis  of  the  result  dilute  the 
phenol  solution  so  that  10  c.c.  contain  i  mg.  of  phenol.  Five  c.c.  of  this  solution 
(equivalent  to  0.5  mg.  of  phenol),  when  10  c.c.  of  the  phosphotungstic  phospho- 
molybdic  reagent  and  25  c.c.  of  saturated  sodium  carbonate  solution  are  added,  and 
the  whole  made  up  with  water  at  about  3o°C.  to  100  c.c.,  give  when  set  in  the 
colorimeter  at  20  mm.  a  convenient  standard. 

Calculation. — The  filtrate  used  for  the  determination  of  free  and  total  phenols 

1  This  reagent  is  prepared  as  follows:  Boil  together  for  two  hours  (using  a  reflux  con- 
denser) 100  grams  of  sodium  tungstate,  20  grams  of  phosphomolybdic  acid  (or  an  equiva- 
lent of  molybdic  acid),  50  c.c.  of  phosphoric  acid  (85  per  cent),  and  75  c.c.  of  .distilled 
water.  After  the  period  of  heating,  cool,  dilute  to  i  liter  with  distilled  water,  and  filter 
if  necessary. 


URINE  561 

contains  the  phenols  from  one-half  the  amount  of  urine  analyzed.  The  actual 
determination  of  phenols,  both  free  and  total,  is  made  upon  a  two-fifths  portion 
of  this  filtrate  and  this  amount  of  filtrate  contains  the  phenols  from  one-fifth 
of  the  amount  of  urine  analyzed.  In  the  determination  of  free  phenols  the  colored 
solution  is  diluted  to  only  half  that  of  the  standard  while  in  the  determination 
of  total  phenols  the  dilution  is  the  same  as  that  of  the  standard. 
Hence, 

•n 

n — ^ —  =  milligrams  of  free  phenol 

K.2  X  4 

and 

T> 

p     *      =  milligrams  of  total  phenol 

•K.2  X  2 

in  2  c.c.  or  4  c.c.  of  urine  according  to  whether  10  c.c.  or  20  c.c.  of  urine  was 
taken  for  analysis,  when  Ri  is  taken  as  the  reading  obtained  with  the  standard 
solution,  and  R2  is  taken  as  the  reading  obtained  with  the  unknown. 

Interpretation. — This  method  determines  all  phenolic  substances 
e.g.,  the  volatile  phenols  p-cresol  and  phenol,  the  non- volatile  phenol 
pyrocatechol  and  the  aromatic  oxyacids  p-oxyphenylacetic  acid,  p- 
oxyphenylpropionic  acid  and  p-oxybenzoic  acid.  All  these  substances 
are  formed  from  tyrosine.  By  this  method  total  phenol  excretions  of 
from  0.2-0.5  gram  per  day  have  been  noted  in  normal  individuals. 
These  results  are  much  higher  than  figures  previously  obtained  by  other 
methods.  The  free  phenols  varied  from  0.1-0.3  gram  per  day.  The 
total  phenol  excretion  appears  to  vary  directly  but  not  proportionately 
with  the  protein  intake.  The  amount  of  conjugated  phenol  indicates 
the  extent  to  which  the  phenols  have  been  detoxicated.  The  excretion 
of  phenols  is  increased  in  gastro-intestinal  disorders  associated  with 
increased  putrefaction.  It  is  increased  by  the  ingestion  of  phenols  or 
of  benzene.  Constipation  influences  the  phenol  output  to  a  greater 
extent  than  diet.1  Diets  which  promote  the  growth  of  putrefactive 
bacteria  also  promote  indican  and  phenol  excretion.  A  high  phenol 
output  does  not  necessarily  mean  a  high  indican  excretion. 

TisdalPs  Modification  of  Folin-Denis  Method.2— Principle.— The 
phenolic  substances  are  extracted  from  the  urine  with  ether,  the  ether 
solution  extracted  with  10  per  cent  NaOH,  and  the  phenols  determined 
colorimetrically  as  in  Folin-Denis  method  p.  559. 

Procedure  for  Free  Volatile  Phenols. — Five  c.c.  of  urine  are  shaken  for  five 
minutes  with  100  c.c.  of  ether.  The  urine  is  separated  and  two  more  extrac- 
tions are  made,  using  50  c.c.  of  ether  each  time.  The  200  c.c.  of  ether  are 
shaken  for  5  minutes  with  20  c.c.  of  10  per  cent  NaOH,  separated,  and  the 
sodium  hydroxide  solution  is  neutralized  and  made  slightly  acid  with  concen- 
trated HC1.  Sodium  carbonate  and  the  phenol  reagent  are  then  added  as  in  the 
Folin-Denis  method  p.  559. 

1  Underbill  and  Simpson:  Jour.  Biol.  Chem.,  44,  69,  1920. 
2Tisdall:  Jour.  Biol.  Chem.,  44,  409,  1920. 
36 


562  PHYSIOLOGICAL   CHEMISTRY 

Procedure  for  Total  Volatile  'Phenols. — The  second  filtrate  from  the  Folin- 
Denis  procedure  is  treated  as  outlined  by  Folin  and  Denis  for  the  deconjugation 
of  phenols  and  then  extracted  with  ether  as  in  Tisdall's  procedure  for  free  volatile 
phenols  (see  above). 

Interpretation. — Results  for  total  phenolic  substances  obtained  by 
this  method  are  at  least  50  per  cent  lower  than  those  recorded  by 
Folin  and  Denis.  By  the  Tisdall  method  only  a  small  fraction  of 
the  volatile  phenols  are  found  to  be  excreted  in  the  free  state.  The 
substances  causing  the  difference  in  results  by  the  two  methods  remain 
undetermined.  For  additional  notes  on  interpretation  see  Folin-Denis 
method  p.  561. 

Oxalic  Acid 

SalkowsM-Autenreith  and  Earth  Method. — Principle. — The  oxalic  acid  is  pre- 
cipitated by  means  of  CaCU.  From  the  solution  of  this  precipitate  in  hydrochloric 
acid  the  oxalic  acid  is  extracted  with  ether  and  reprecipitated  as  calcium  oxalate. 

Procedure. — Place  the  24-hour  urine  specimen  in  a  precipitating  jar,  add  an 
excess  of  calcium  chloride,  render  the  urine  strongly  ammoniacal,  stir  it  well,  and 
allow  it  to  stand  18-20  hours.  Filter  off  the  precipitate,  wash  it  with  a  small 
amount  of  water  and  dissolve  it  in  about  30  c.c.  of  a  hot  15  per  cent  solution  of 
hydrochloric  acid.  By  means  of  a  separatory  funnel  extract  the  solution  with  150 
c.c.  of  ether  which  contains  3  per  cent  of  alcohol,  repeating  the  extraction  four  or 
five  times  with  fresh  portions  of  ether.  Unite  the  ethereal  extracts,  allow  them  to 
stand  for  an  hour  in  a  flask,  and  then  filter  through  a  dry  filter  paper.  Add  5  c.c. 
of  water  to  the  filtrate,  to  prevent  the  formation  of  diethyl  oxalate  when  the  solu- 
tion is  heated,  and  distil  off  the  ether.  If  necessary,  decolorize  the  liquid  with 
animal  charcoal  and  filter.  Concentrate  the  filtrate  to  3-5  c.c.,  add  a  little  calcium 
chloride  solution,  make  it  ammoniacal,  and  after  a  few  minutes  render  it  slightly 
acid  with  acetic  acid.  Allow  the  acidified  solution  to  stand  several  hours,  collect 
the  precipitate  of  calcium  oxalate  on  a  washed  filter  paper,1  wash,  incinerate  strongly 
(to  CaO),  and  weigh  in  the  usual  manner. 

Calculation. — Since  56  parts  of  CaO  are  equivalent  to  90  parts  of  oxalic  acid, 
the  quantity  of  oxalic  acid  in  the  volume  of  urine  taken  may  be  determined  by 
multiplying  the  weight  of  CaO  by  the  factor  of  1.6071. 

Interpretation. — From  15-20  mg.  of  oxalic  acid  are  excreted  by  a  normal  adult 
on  an  ordinary  mixed  diet.  It  arises  from  oxalates  of  the  food  ingested  and  from 
fat  and  protein  metabolism.  It  is  increased  by  the  ingestion  of  apples,  grapes, 
cabbage,  etc.,  although  most  of  the  ingested  oxalate  is  destroyed.  It  is  increased 
in  disturbances  of  metabolism  associated  with  decreased  oxidation,  according  to 
certain  observers.  The  term  "oxaluria"  has  been  largely  a  misnomer. 

Sulphur 
(a)  Gravimetric  Procedures 

I.  Total   Sulphates.— Folin1  s   Method.— Principle. — The    sulphuric 
acid  of  the  conjugated  sulphates  is  set  free  by  boiling  with  acid.     The 
total  sulphates  are  then  precipitated  with  barium  chloride. 
1  Schleicher  and  Schiill,  No.  589,  is  satisfactory. 


TOINE  563 

Procedure. — Place  25  c.c.  of  urine  in  a  200-250  c.c.  Erlenmeyer  flask,  add 
20  c.c.  of  dilute  hydrochloric  acid1  (i  volume  of  concentrated  HC1  to  4  volumes  of 
water)  and  gently  boil  the  mixture  for  20-30  minutes.  To  minimize  the  loss  of 
water  by  evaporation  the  mouth  of  the  flask  should  be  covered  with  a  small  watch 
glass  during  the  boiling  process.  Cool  the  flask  for  2 -3  minutes  in  running  water, 
and  dilute  the  contents  to  about  150  c.c.  by  means  of  cold  water.  Add  10  c.c. 
of  a  5  per  cent  solution  of  barium  chloride  slowly,  drop  by  drop,  to  the  cold  solu- 
tion.2 The  contents  of  the  flask  should  not  be  stirred  or  shaken  during  the  addi- 
tion of  the  barium  chloride.  Allow  the  mixture  to  stand  at  least  one  hour,  then 
shake  up  the  solution  and  filter  it  through  a  weighed  Gooch  crucible.3 

Wash  the  precipitate  of  BaSO4  with  about  250  c.c.  of  cold  water,  dry  it  hi  an 
air-bath  or  over  a  very  low  flame,  then  ignite,4  cool  and  weigh. 

Calculation. — Subtract  the  weight  of  the  Gooch  crucible  from  the  weight  of 
the  crucible  and  the  BaSo4  precipitate  to  obtain  the  weight  of  the  precipitate. 
The  weight  of  SOa5  in  the  volume  of  urine  taken  may  be  determined  by  means  of 
the  following  proportion. 

Mol.  Wt.        Wt.  of  Mol.  wt. 

BaSO4  :  BaSO4  :  :  SO3  :  x(wt.    of  SO3  in  grams). 

Representing  the  weight  of  the  BaSO4  precipitate  by  y  and  substituting  the  proper 
molecular  weights,  we  have  the  following  proportion: 

233 -43  :  y  :  :  80.06  :  x  (wt.  of  SO 3  in  grams  in  the  quantity  of  urine  used). 

Calculate  the  quantity  of  SO  3  in  the  twenty-four-hour  specimen  of  urine. 

To  express  the  result  in  percentage  of  SO3  simply  divide  the  value  of  x,  as  just 
determined,  by  the  quantity  of  urine  used. 

i 

Interpretation. — The  total  sulphate  excretion  (ethereal  and  inorganic 
sulphates)  by  a  normal  adult  on  a  mixed  diet  is  usually  between  1.5  and 
3.0  gram  of  80s  with  an  average  of  about  2.0  gram.  The  sulphuric 
acid  is  derived  but  to  a  slight  extent  ordinarily  from  ingested  sul- 
phates, being  mainly  dependent  on  the  sulphur  of  the  protein  ingested 
and  will  consequently  vary  widely  with  the  protein  content  of  the  diet. 

1  If  it  is  desired,  50  c.c.  of  urine  and  4  c.c.  of  concentrated  acid  may  be  used  instead. 

2  A  dropper  or  capillary  funnel  made  from  an  ordinary  calcium  chloride  tube  and  so 
constructed  as  to  deliver  10  c.c.  in  2-3  minutes  is  recommended  for  use  in  adding  the  barium 
chloride. 

3  If  a  Gooch  crucible  is  not  available,  the  precipitate  of  BaSO4  may  be  filtered  off  upon 
a  washed  filter  paper  (Schleicher  &  SchiilTs,  No.  589,  blue  ribbon),  and  after  washing  the 
precipitate  with  about  250  c.c.  of  cold  water  the  paper  and  precipitate  may  be  dried  in  an 
air-bath  or  over  a  low  flame.    The  ignition  may  then  be  carried  out  in  the  usual  way  in  the 
ordinary  platinum  or  porcelain  crucible.    In  this  case  correction  must  be  made  for  the 
weight  of  the  ash  of  the  filter  paper  used. 

4  Care  must  be  taken  in  the  ignition  of  precipitates  in  Gooch  crucibles.    The  flame 
should  never  be  applied  directly  to  the  perforated  bottom  or  to  the  sides  of  the  crucible,  since 
such  manipulation  is  invariably  attended  by  mechanical  losses.    The  crucibles  should 
always  be  provided  with  lids  and  tight  bottoms  during  the  ignition.    In  case  porcelain  Gooch 
crucibles,  whose  bottoms  are  not  provided  with  a  non-perforated  cap,  are  used,  the  crucible 
may  be  placed  upon  the  lid  of  an  ordinary  platinum  crucible  during  ignition.    The  lid 
should  be  supported  on  a  triangle,  the  crucible  placed  upon  the  lid  and  the  flame  applied 
to  the  improvised  bottom.    Ignition  should  be  complete  in  10  minutes  if  no  organic  matter 
is  present. 

6  It  is  considered  preferable  by  many  investigators  to  express  all  sulphur  values  in  terms 
of  S  rather  than  SO3. 


564  PHYSIOLOGICAL   CHEMISTRY 

From  75  to  95  per  cent  of  the  total  sulphur  of  the  urine  is  ordinarily 
found  as  sulphate,  the  proportion  being  greatest  on  a  high  protein  diet. 
The  sulphate  excretion  is  increased  in  all  conditions  associated  with 
increased  decomposition  of  body  protein  as  in  acute  fevers  and  de- 
creased whenever  there  is  a  decrease  in  metabolic  activity. 

2.  Inorganic  Sulphates. — Folin's  Method. — Place  25  c.c.  of  urine  and  100 
c.c.  of  water  in  a  200-250  c.c.  Erlenmeyer  flask  and  acidify  the  diluted  urine 
with  10  c.c.  of  dilute  hydrochloric  acid  (i  volume  of  concentrated  HC1  to  4  vol- 
umes of  water).    In  case  the  urine  is  dilute  50  c.c.  may  be  used  instead  of  25  c.c. 
and  the  volume  of  water  reduced  proportionately.    Add  10  c.c.  of  5  per  cent  bar- 
ium chloride  slowly,  drop  by  drop,  to  the  cold  solution  and  from  this  point  proceed 
as  indicated  in  the  method  for  the  determination  of  Total  Sulphates,  page  562. 

Calculate  the  quantity  of  inorganic  sulphates,  expressed  as  SOs,  in  the  twenty- 
four-hour  urine  specimen. 

Calculation. — Calculate  according  to  the  directions  given  under  Total  Sul- 
phates, above. 

Interpretation. — On  an  average  about  90  per  cent  of  the  total  sul- 
phates of  the  urine  exists  as  inorganic  sulphates  but  the  proportion 
of  the  sulphates  existing  in  this  form  varies  widely,  being  greater  on 
a  high  protein  diet  than  on  a  very  low  protein  diet.  The  amount 
varies  with  the  total  sulphates  (which  see). 

3.  Ethereal   Sulphates. — Folin's   Method. — Principle. — The   inorganic   sul- 
phates are  removed  with  barium  chloride  and  the  conjugated  sulphates  then 
determined  after  hydrolysis. 

Procedure. — Place  125  c.c.  of  urine  in  an  Erlenmeyer  flask  of  suitable  size, 
dilute  it  with  75  c.c.  of  water  and  acidify  the  mixture  with  30  c.c.  of  dilute  hydro- 
.chloric  acid  (i  volume  of  concentrated  HC1  to  4  volumes  of  water).  To  the  cold 
solution  add  20  c.c.  of  a  5  per  cent  solution  of  barium  chloride,  drop  by  drop.1 
Allow  the  mixture  to  stand  about  one  hour,  then  filter  it  through  a  dry  filter  paper.2 
Collect  125  c.c.  of  the  filtrate  and  boil  it  gentry  for  at  least  one-half  hour.  Cool 
the  solution,  filter  off  the  precipitate  of  BaSO4,  wash,  dry  and  ignite  it  according  to 
the  directions  given  on  page  563. 

Calculation. — The  weight  of  the  BaSO4  precipitate  should  be  multiplied  by 
2  since  only  one-half  (125  c.c.)  of  the  total  volume  (250  c.c.)  of  fluid  was  precipi- 
tated by  the  barium  chloride.  The  remaining  calculation  should  be  made  accord - 
ing  to  directions  given  under  Total  Sulphates,  page  563. 

Calculate  the  quantity  of  ethereal  sulphates,  expressed  as  SO3,  in  the  twenty- 
four-hour  urine  specimen. 

Interpretation. — The  excretion  of  ethereal  sulphates  (expressed  as 
SOs)  varies  ordinarily  from  o.i  to  0.25  gram  per  day  comprising  from 

1  See  note  (2)  at  the  bottom  of  p.  563. 

1  This  precipitate  consists  of  the  inorganic  sulphates.  If  it  is  desired,  this  BaSO4 
precipitate  may  be  collected  in  a  Gopch  crucible  or  on  an  ordinary  quantitative  filter 
paper  and  a  determination  of  inorganic  sulphates  made,  using  the  same  technic  as  that 
suggested  above.  In  this  way  we  are  enabled  to  determine  the  inorganic  and  ethereal 
sulphates  in  the  same  sample  of  urine. 


URINE  565 

5  to  15  per  cent  of  the  total  sulphur  excretion.  The  absolute  amount 
of  ethereal  sulphate  increases  with  increase  in  the  protein  of  the  diet  and 
particularly  with  increase  of  putrefactive  processes  in  the  intestine  or 
elsewhere.  The  amount  excreted  cannot  however  be  taken  as  an 
index  of  the  extent  of  intestinal  putrefaction. 

4.  Total  Sulphur.— Benedict's  Method.1— Principle.— The  urine 
is  evaporated  and  ignited  with  a  solution  of  copper  nitrate  and 
potassium  chlorate.  Organic  matter  is  thus  destroyed  and  all  un- 
oxidized  sulphur  is  oxidized  to  the  sulphate  form  and  can  be  readily 
precipitated  with  barium  chloride  in  the  usual  manner.  The  method 
is  very  convenient  and  accurate. 

Ten  c.c.  of  urine  are  measured  into  a  small  (7-8  cm.)  porcelain  evaporating  dish 
and  5  c.c.2  of  Benedict's  sulphur  reagent3  added.  The  contents  of  the  dish  are 
evaporated  over  a  free  flame  which  is  regulated  to  keep  the  solution  just  below  the 
boiling-point,  so  that  there  can  be  no  loss  through  spattering.  When  dryness  is 
reached  the  flame  is  raised  slightly  until  the  entire  residue  has  blackened.  The 
flame  is  then  turned  up  in  two  stages  to  the  full  heat  of  the  bunsen  burner  and  the 
contents  of  the  dish  thus  heated  to  redness  for  ten  minutes  after  the  black  residue 
(which  first  fuses)  has  become  dry.  This  heating  is  to  decompose  the  last  traces 
of  nitrate  (and  chlorate) .  The  flame  is  then  removed  and  the  dish  allowed  to  cool 
more  or  less  completely.  Ten  to  20  c.c.  of  dilute  (i  :  4)  hydrochloric  acid  is  then 
added  to  the  residue  in  the  dish,  which  is  then  warmed  gently  until  the  contents 
have  completely  dissolved  and  a  perfectly  clear,  sparkling  solution  is  obtained. 
This  dissolving  of  the  residue  requires  scarcely  two  minutes.  With  the  aid  of  a 
stirring  rod  the  solution  is  washed  into4  a  small  Erlenmeyer  flask,  diluted  with 
cold,  distilled  water  to  100-150  c.c.,  10  c.c.  of  10  per  cent  barium  chloride  solution 
added  drop  by  drop,  and  the  solution  allowed  to  stand  for  about  an  hour.  It  is 
then  shaken  up  and  filtered  as  usual  through  a  weighted  Gooch  crucible.  Controls 
should  be  run  on  the  oxidizing  mixture. 

Calculation. — Make  the  calculation  according  to  directions  given  under  Total 
Sulphates,  page  563.  Calculate  the  quantity  of  sulphur  expressed  as  SOa  or  S, 
present  in  the  twenty-four-hour  urine  specimen. 

Interpretation. — The  total  sulphur  (S03)  excretion  averages  about  2.5 
grams  per  day.  It  runs  more  or  less  parallel  with  the  decomposition 

1  Benedict:  Journal  of  Biological  Chemistry,  6,  363,  1909. 

2  If  the  urine  is  concentrated  the  quantity  should  be  slightly  increased. 

1  Crystallized  copper  nitrate,  sulphur-free  or  of  known  sulphur  content 200  grams. 

Sodium  or  potassium  chlorate 50  grams. 

Distilled  water  to 1000  c.c. 

Denis  has  suggested  the  use  of  the  following  solution: 

Copper  nitrate 25  grams. 

Sodium  chloride. 25  grams. 

Ammonium  nitrate 10  grams. 

Water  to  make 100  c.c. 

The  procedure  is  the  same  as  the  above  except  that  25  c.c.  of  urine  and  5  c.c.  of  reagent 
are  taken.  It  gives  accurate  results. 

4  Sometimes  the  porcelain  glaze  cracks  during  heating,  in  which  case  the  solution  should 
be  filtered  into  the  flask. 


566  PHYSIOLOGICAL   CHEMISTRY 

of  endogenous  and  exogenous  protein  and  a  definite  ratio  between  the 
excretion  of  total  N  and  total  S  might  be  expected.  It  has  been 
suggested  that  the  ratio  5  :  i  expresses  this  relation  in  a  general  way  but 
no  constant  value  can  be  given.  See  Total  Sulphates. 

5.  Total      Sulphur. — Osborne-Folin      Method.-— Principle. — This 
method  depends  on  the  destruction  of  organic  matter  by  means  of 
sodium  peroxide.     It  is  employed  particularly  for  the  determination 
of  sulphur  in  foods  and  feces.     Benedict's  procedure  (see  above)  is 
simpler  and  fully  as  satisfactory  for  urine. 

Place  25  c.c.  of  urine1  in  a  200-250  c.c.  nickel  crucible  and  add  about  3  grams  of 
sodium  peroxide.  Evaporate  the  mixture  to  a  syrup  upon  a  steam  water-bath  and 
heat  it  carefully  over  an  alcohol  flame  until  it  solidifies  (15  minutes) .  Now  remove 
the  crucible  from  the  flame  and  allow  it  to  cool.  Moisten  the  residue  with  i -2  c.c.  of 
water,2  sprinkle  about  7-8  grams  of  sodium  peroxide  over  the  contents  of  the 
crucible  and  fuse  the  mass  over  an  alcohol  flame  for  about  10  minutes.  Allow  the 
crucible  to  cool  for  a  few  minutes,  add  about  100  c.c  of  water  to  the  contents  and 
heat  at  least  one-half  hour  over  an  alcohol  flame  to  dissolve  the  alkali  and 
decompose  the  sodium  peroxide.  Next  rinse  the  mixture  into  a  400-450  c.c. 
Erlenmeyer  flask,  by  means  of  hot  water,  and  dilute  it  to  about  250  c.c.  Heat 
the  solution  nearly  to  the  boiling-point  and  add  concentrated  hydrochloric  acid 
slowly  until  the  nickelic  oxide,  derived  from  the  crucible,  is  just  brought  into 
solution.3  A  few  minutes'  boiling  should  now  yield  a  clear  solution.  In  case 
too  little  peroxide  or  too  much  water  was  added  for  the  final  fusion  a  clear 
solution  will  not  be  obtained.  In  this  event  cool  the  solution  and  remove  the 
insoluble  matter  by  filtration. 

To  the  clear  solution  add  5  c.c.  of  very  dilute  alcohol  (about  18-20  per  cent)  and 
continue  the  boiling  for  a  few  minutes.  The  alcohol  is  added  to  remove  the 
chlorine  which  was  formed  when  the  solution  was  acidified.  Add  10  c.c.  of  a 
10  per  cent  solution  of  barium  chloride,  slowly,  drop  by  drop,4  to  the  liquid. 
Allow  the  precipitated  solution  to  stand  in  the  cold  two  days  and  then  filter  and 
continue  the  manipulation  according  to  the  directions  given  under  Total  Sul- 
phates, page  563. 

Calculation. — Make  the  calculation  according  to  directions  given  under  Total 
Sulphates,  page  563.  Calculate  the  quantity  of  sulphur,  expressed  as  SO 3  or  S, 
present  in  the  twenty-four-hour  urine  specimen. 

Interpretation.— See  page  565. 

(b)  Volumetric  Procedures 

6.  Volumetric  Determination  of  Ethereal  and  Inorganic  Sulphates. 
— Method  of  Rosenheim  and  Drummond.5 — Principle. — The  sulphates 
of  the  urine  are  precipitated  by  means  of  benzidine  solution,  the  pre- 

1  If  the  urine  is  very  dilute  50  c.c.  may  be  used. 

8  This  moistening  of  the  residue  with  a  small  amount  of  water  is  very  essential  and 
should  not  be  neglected. 

8  About  1 8  c.c.  of  acid  are  required  for  8  grams  of  sodium  peroxide. 

4  See  note  (2)  at  the  bottom  of  p.  563. 

5  Rosenheim  and  Drummond:  Biochem.  J.,  8,  143,  1914. 


URINE  567 

cipitate  of  benzidine  suphate  being  filtered  off  and  the  sulphuric 
acid  of  the  compound  titrated  with  N/io  KOH  using  phenolphthalein 
as  an  indicator.  This  is  possible  because  the  benzidine  is  a  very  weak 
base  and  its  sulphate  readily  dissociates.  It  is  necessary  that  excess 
of  HC1  be  avoided  in  the  precipitation  process. 

Procedure. — (a)  Inorganic  Sulphates. — Preparation  of  the  benzidine  solu- 
tion. Rub  4  grams  of  benzidine  (Kahlbaum)  into  a  fine  paste  with  about  10 
c.c.  of  water  and  transfer  to  a  2 -liter  flask  with  the  aid  of  about  500  c.c.  of  water. 
Add  5  c.c,  of  concentrated  HC1  (sp.  gr.  1.19)  and  make  up  to  2  liters  with  distilled 
water.  One  hundred  and  fifty  c.c.  of  this  solution,  which  keeps  indefinitely, 
are  sufficient  to  precipitate  o.i  gram  H2SO4. 

Measure  25  c.c.  of  urine  into  a  250  c.c.  Erlenmeyer  flask  and  acidify  with 
dilute  hydrochloric  acid  (i  :  4)  until  the  reaction  is  distinctly  acid  to  Congo  red 
paper.  Usually  1-2  c.c.  of  dilute  acid  are  required.  One  hundred  c.c.  of  the 
benzidine  solution,  as  prepared  above,  are  then  run  in  and  the  precipitate, 
which  forms  in  a  few  seconds,  allowed  to  settle^for  ten  minutes.  Filter  with 
suction  and  wash  the  precipitate  with  10-20  c.c.  of  water  saturated  with  benzidine 
sulphate.1  Transfer  the  precipitate  and  filter  paper  to  the  original  precipitation 
flask  with  about  50  c.c.  of  water  and  titrate  hot  with  N/io  KOH,  after  first 
adding  a  few  drops  of  saturated  alcoholic  solution  of  phenolphthalein. 

Calculation.— One  c.c.  of  N/io  KOH  corresponds  to  4.9  mg.  H2SO4  or  4.0  mg. 
of  SO3.  Multiply  the  number  of  cubic  centimeters  of  N/io  KOH  required  by 
4.9  and  by  4  to  get  the  amount  of  H2SO4  in  100  c.c.  of  the  urine  analyzed. 

(b)  Total  Sulphates   (Inorganic  and  Ethereal).— Measure  25  c.c.  of  urine 
into  an  Erlenmeyer  flask,  add  2-2.5  c.c.  of  dilute  HC1  (i :  4)  and  20  c.c.  of  water 
and  boil  for  15-20  minutes.    The  ethereal  sulphates  are  hydrolized.2    Allow  the 
solution  to  cool  and  then  precipitate  the  sulphate  with  benzidine  as  in  the  deter- 
mination of  inorganic  sulphates.    The  titration  and  calculation  are  also  carried 
out  hi  the  same  way. 

(c)  Ethereal  Sulphates.— Determine  the  total  sulphates  and  inorganic  sul- 
phates as  indicated  above.    Subtract  the  amount  of  inorganic  sulphate  from 
that  of  the  total  sulphate  and  obtain  the  amount  of  ethereal  sulphate  present. 

(d)  Total  Sulphur. — According  to  Rosenheim  and  Drummond3  the  benzidine 
method  may  be  employed  for  the  estimation  of  total  sulphur  in  the  solution  ob- 
tained on  the  oxidation  of  urine  by  the  Wolf-Osterberg4  modification  of  Bene- 
dict's method.    This  modification  involves  the  use  of  larger  quantities  of  urine 
than  the  Benedict  method  or  a  reduction  in  accuracy  and  hence  probably  has 
no  advantages  over  Benedict's  original  procedure. 

1  In  order  to  obtain  accurate  results  it  is  most  important  that  the  precipitate  should  be 
finely  suspended  in  water  before  titration  and  this  again  entails  certain  precautions  during 
filtration  so  as  to  prevent  the  caking  together  of  the  precipitate.    The  authors  use  a  funnel 
of  6 

or  with 

2  A  larger  amount  of  HC1  may  be  used  (20  c.c.  of  the  dilute  acid)  if  desired.    In  this 
case  it  is  necessary  to  neutralize  the  solution  carefully  after  boiling  and  again  add  dilute 
HC1  until  the  reaction  is  acid  to  Congo  red. 

3  Rosenheim  and  Drummond:  Bioch.  Jour.,  8,  143,  1914* 

4  Wolf  and  Osterberg:  Bioch.  ZeiL,  29,  429,  1910. 


568  PHYSIOLOGICAL  CHEMISTRY 

(e)  Neutral  Sulphur.  —  Neutral  sulphur  is  most  readily  determined  by  dif- 
ference. Subtract  from  the  total  sulphur  as  determined  by  one  of  the  methods 
given  above  the  amount  of  total  sulphates. 

Interpretation.  —  The  neutral  sulphur  of  the  urine  is  made  up  of 
cystine  and  related  bodies,  thiocyanate,  oxyproteic  acids,  etc.  It  • 
makes  up  ordinarily  from  5-25  per  cent  of  the  total  sulphur  of  the  urine, 
or  on  the  average  0.2  to  0.4  gram  per  day  calculated  as  SOs.  The 
absolute  amount  is  fairly  constant  for  a  given  individual  through  wide 
variations  of  protein  intake,  indicating  that  its  origin  is  mainly  en- 
dogenous, that  is,  that  it  arises  principally  from  the  decomposition  of 
tissue  protein.  On  this  account  the  percentage  of  the  total  sulphur 
excretion  existing  in  the  neutral  form  may  rise  to  25  per  cent  on  a  very 
low  protein  diet  and  decrease  to  5  per  cent  on  a  high  protein  diet,  the 
absolute  amount  remaining  nearly  constant.  In  fasting  percentages 
as  high  as  70  have  been  noted.  In  many  disorders  as  tuberculosis, 
cancer,  cystinuria,  etc.,  the  amount  may  be  relatively  and  in  some 
cases  absolutely  increased  but  no  fixed  relations  have  been  determined 
for  the  various  conditions. 

Phosphorus 

i.  Total  Phosphates.  —  Uranium  Acetate  Method.  —  Principle.  — 
Standard  uranium  acetate  is  run  into  a  measured  quantity  of  urine 
until  all  of  the  phosphate  has  been  precipitated  as  insoluble  uranium 
phosphate.  An  excess  of  uranium  is  indicated  by  a  reddish  coloration 
with  potassium  ferrocyanide.  This  method  is  accurate  and  gives 
practically  the  total  phosphorus  of  urine  inasmuch  as  the  latter  exists 
generally  almost  entirely  as  phosphates. 

Procedure.  —  To  50  c.c.  of  urine1  in  a  small  beaker  or  Erlenmeyer  flask  add 
5  c.c.  of  a  special  sodium  acetate  solution2  and  heat  the  mixture  to  the  boiling- 
point.  From  a  burette,  run  into  the  hot  mixture,  drop  by  drop,  a  standard  solu- 
tion of  uranium  acetate3  until  a  precipitate  ceases  to  form  and  a  drop  of  the  mix- 
ture  when  removed  by  means  of  a  glass  rod  and  brought  into  contact  with  a 


(Jour.  Biol.  Chem.,  46,  285,  1921)  has  suggested  a  method  which  is  applicable 
to  small  volumes  of  urine. 

2  The  sodium  acetate  solution  is  prepared  by  dissolving  100  grams  of  sodium  acetate  in 
800  c.c.  of  distilled  water,  adding  100  c.c.  of  30  per  cent  acetic  acid  to  the  solution,  and 
making  the  volume  of  the  mixture  up  to  i  liter  with  water. 

3  Uranium  Acetate  Solution.  —  Dissolve  about  35.0  grams  of  uranium  acetate  in  i  liter 
of  water  with  the  aid  of  heat  and  3-4  c.c.  of  glacial  acetic  acid.    Let  stand  a  few  days 
and  filter.     Standardize  against  a  phosphate  solution  containing  0.005  gram  of  P2O»  per 
cubic  centimeter.     For  this  purpose  dissolve  14.721  grams  of  pure  air-dry  sodium  am- 
monium phosphate  (NaNH4HPO4+4H2O)  in  water  to  make  a  liter.    To  20  c.c.  of  this 
phosphate  solution  in  a  200  c.c.  beaker  add  30  c.c.  of  water  and  5  c.c.  of  sodium  acetate 
solution  (see  above)  and  titrate  with  the  uranium  solution  to  the  correct  end  reaction  as 
indicated  in  the  method  above.    If  exactly  20  c.c.  of  uranium  solution  are  required  i  c.c. 
of  the  solution  is  equivalent  to  0.005  gram  PjOB.    If  stronger  than  this  dilute  accordingly 
and  check  again  by  titration. 


URINE  569 

drop  of  a  solution  of  potassium  ferrocyanide1  on  a  porcelain  test-tablet  produces 
instantaneously  a  brownish-red  coloration.2  Take  the  burette  reading  and 
calcu'ate  the  P2O6  content  of  the  urine  under  examination. 

Calculation. — Multiply  the  number  of  cubic  centimeters  of  uranium  acetate 
solution  used  by  0.005  to  determine  the  number  of  grams  of  P2O6  in  the  50  c.c. 
of  urine  used.  To  express  the  result  in  percentage  of  P2O6  multiply  the  value 
just  obtained  by  2,  e.g.,  if  50  c.c.  of  urine  contained  0.074  gram  of  P2O5  it  would 
be  equivalent  to  0.148  per  cent. 

Calculate,  in  terms  of  P205,  the  total  phosphate  content  of  the  24- 
hour  urine  specimen. 

Interpretation. — The  excretion  of  phosphoric  add  is  extremely 
variable  but  on  the  average  the  total  output  for  the  24  hours  is  about 
2.5  grams  expressed  as  PzOs.  Ordinarily  the  total  output  is  mainly  in 
the  form  of  phosphates  and  is  distributed  between  alkaline  and  earthy 
phosphates  in  the  ratio  of  2 :  i  but  this  is  likewise  inconstant.  The 
greater  part  of  the  phosphate  excretion  arises  from  the  ingested  food, 
either  from  the  preformed  phosphates  or  more  especially  from  the 
organic  combinations  as  phospho-  and  nucleoproteins.  The  |  ex- 
cretion is  consequently  very  largely  dependent  upon  the  phosphorus 
content  of  the  diet.  Some  of  the  phosphoric  acid  results  from  the 
breakdown  of  the  tissues  of  the  body,  and  this  endogenous  phosphoric 
acid  excretion  is  increased  in  conditions  of  increased  metabolism  as  in 
fevers.  The  findings  in  pathological  conditions  have  been  somewhat 
contradictory  due  to  lack  of  control  of  diet.  The  so-called  "phos- 
phaturias"  nearly  always  represent  decreased  acidity  and  not  in- 
creased phosphate  content  of  the  urine.  Such  conditions  are,  however, 
significant  as  indicating  a  possible  tendency  to  the  formation  of  phos- 
phatic  calculi. 

2.  Earthy  Phosphates. — Principle. — The  earthy  phosphates  are 
precipitated  by  making  the  urine  alkaline.  The  precipitate  is  filtered 
off,  dissolved  in  acid  and  titrated  with  uranium  acetate. 

Procedure. — To  100  c.c.  of  urine  hi  a  beaker  add  an  excess  of  ammonium 
hydroxide  and  allow  the  mixture  to  stand  12-24  hours.  Under  these  conditions 
the  phosphoric  acid  hi  combination  with  the  alkaline  earths,  calcium  and  mag- 
nesium, is  precipitated  as  phosphates  of  these  metals.  Collect  the  precipitate 
on  a  filter  paper  and  wash  it  with  very  dilute  ammonium  hydroxide.  Pierce 
the  paper,  and  remove  the  precipitate  by  means  of  hot  water.  Bring  the  phos- 
phates into  solution  by  adding  a  small  amount  of  dilute  acetic  acid  to  the  warm 
solution.  Make  the  volume  up  to  50  c.c.  with  water,  add  5  c.c.  of  sodium  acetate 

xCochineal  in  30  per  cent  alcohol  may  be  used  as  an  indicator.  If  employed  it  is  added 
directly  to  the  urine  after  the  uranium  acetate  titration  produces  no  further  precipitate. 
A  green  color  is  the  end  reaction.  The  use  of  cochineal  is  more  convenient  but  rather  less 
accurate  than  the  procedure  involving  the  use  of  the  ferrocyanide. 

2  A  10  per  cent  solution  of  potassium  ferrocyanide  is  satisfactory. 


570  PHYSIOLOGICAL   CHEMISTRY 

solution,  and  determine  the  P2O5  content  of  the  mixture  according  to  the  direc- 
tions given  under  the  previous  method. 

Calculation. — Multiply  the  number  of  cubic  centimeters  of  uranium  acetate 
solution  used  by  0.005  to  determine  the  number  of  grams  of  P2O6  in  the  100  c.c. 
of  urine  used.  Since  100  c.c.  of  urine  was  taken  this  value  also  expresses  the 
percentage  of  P2O5  present. 

Calculate  the  quantity  of  earthy  phosphates,  in  terms  of  P2O5,  present  in  the 
24 -hour  urine  specimen. 

The  quantity  of  phosphoric  acid  present  in  combination  with  the  alkali 
metals  may  be  determined  by  subtracting  the  content  of  earthy  phosphates 
from  the  total  phosphates. 

Interpretation. — Ordinarily  the  earthy  phosphates  make  up  from 
30-40  per  cent  of  the  total  phosphate  excretion.  The  amount  varies 
with  the  excretion  of  calcium  and  magnesium  ^  which  see). 

3.  Total  Phosphorus.- — (a)  Volumetric  Procedure. — Principle. — The 
organic  matter  is  destroyed  by  digestion  with  a  mixture  of  sulphuric 
and  nitric  acids  or  some  other,  oxidizing  agent.  The  phosphorus  is  then 
precipitated  as  the  phosphomolybdate  and  determined  gravimetrically 
or  volumetrically. 

Preparation  of  the  Solution. — Pipette  10  c.c.  of  urine  (or  an  amount  of  sub- 
stance containing  about  20  mg.  of  P2O5)  into  a  Kjeldahl  flask.  Add  10  c.c.  of  a 
mixture  of  equal  parts  of  concentrated  H2SO4  and  concentrated  HNO3.  Digest 
over  a  low  flame  until  red  fumes  cease  to  come  off.  If  the  mixture  darkens  due 
to  the  charring  action  of  the  sulphuric  acid,  add  nitric  acid  from  a  separatory 
funnel  a  few  drops  at  a  time  and  continue  the  digestion.  When  the  mixture 
remains  clear  on  evaporation  to  the  point  where  white  sulphuric  fumes  come  off 
the  digestion  is  completed  by  heating  for  10-15  minutes  longer.  Cool  and  transfer 
the  solution  to  a  400  c.c.  Erlenmeyer  flask  with  the  aid  of  enough  water  to 
make  a  total  volume  of  about  75  c.c.1 

Instead  of  oxidizing  the  material  as  described  above  it  may  be 
ignited  with  magnesia  to  destroy  organic  matter.  About  2  grams  of 
the  solid  substance  or  25  c.c.  of  urine  (previously  evaporated  nearly 
to  dryness)  are  mixed  with  a  little  more  than  an  equal  bulk  of  mag- 
nesium oxide  in  a  porcelain  dish  of  about  30  c.c.  capacity.  Five  c.c. 
of  magnesium  nitrate  solution  (see  Reagents  and  Solutions,  page  637) 
are  added  and  the  mixture  heated  very  gently  at  first,  then  gradually 
to  bright  redness.  The  mixture  is  cooled  and  transferred  with  water 
to  a  250  c.c.  flask.  An  excess  (20-30  c.c.)  of  HC1  are  added  and  the 
mixture  boiled  a  few  minutes.  Remove  from  the  flame  and  add  at 
once  enough  barium  chloride  solution  to  precipitate  any  sulphate 
present.  Cool,  make  to  mark,  filter  and  take  an  aliquot  for  analysis. 

1  In  the  case  of  urine  it  is  possible  to  neutralize  this  acid  solution  with  ammonia,  make 
it  acid  with  acetic  acid  and  titrate  with  uranium  acetate  as  in  the  preceding  method. 


URINE  571 

Precipitation  of  the  Phosphomolybdate. — Neutralize  the  solution  with 
ammonia,  make  slightly  acid  with  nitric  acid,  and  add  15  grams  of  ammonium 
nitrate  in  substance  (or  25  c.c.  of  a  60  per  cent  solution).  Heat  on  a  water-bath 
to  6o-6s°C.  (not  higher)  and  add  30-40  c.c.  of  molybdate  solution,1  stir  and  let 
stand  for  about  15  minutes  at  60-65°.  Filter  at  once  through  a  small  paper,2 
washing  the  precipitate  twice  by  decantation  with  i  per  cent  potassium  nitrate 
solution  using  about  25  c.c.  each  time,  stirring  up  the  precipitate  well  in  each 
case,  and  allowing  to  settle.  Transfer  the  precipitate  to  the  filter  and  wash  with 
i  per  cent  potassium  nitrate  solution  until  two  fillings  of  the  filter  (collected 
separately)  do  not  greatly  diminish  the  color  produced  with  phenolphthalein 
by  i  drop  of  the  standard  alkali. 

Titration  of  the  Phosphomolybdate. — Transfer  the  precipitate  and  filter 
back  to  the  original  beaker  and  dissolve  in  a  small  excess  of  N/5  NaOH  (about 
2-3  c.c.  more  than  required  to  completely  dissolve  the  yellow  precipitate).  Add 
about  100  c.c.  of  boiled  and  cooled  water  and  a  few  drops  of  phenolphthalein 
as  an  indicator  (a  red  color  should  be  observed  indicating  excess  of  NaOH) 
and  titrate  the  excess  of  NaOH  with  N/io  acid. 

Calculation.— Divide  the  number  of  cubic  centimeters  of  N/io  acid  required 
by  2  and  subtract  from  the  number  of  cubic  centimeters  of  N/5  NaOH  used. 
This  gives  the  number  of  cubic  centimeters  of  N/5  NaOH  required.  Multiply 
by  0.618  (the  equivalent  of  i  c.c.  of  N/5  NaOH  in  P2O5)  and  obtain  the  number 
of  milligrams  of  P2O6  hi  10  c.c.  of  the  urine  analyzed.  Calculate  the  daily  output 
of  P2O5  in  this  case  from  the  24-hour  volume. 

Interpretation. — Nearly  all  of  the  phosphorus  of  the  urine  exists  as 
alkali  and  earthy  phosphates.  Consequently  the  total  phosphorus 
varies  in  the  same  way  as  the  total  phosphates  (which  see).  A  small 
portion  of  the  phosphorus  of  the  urine  may  exist  in  organic  com- 
bination though  never  in  a  reduced  form.  This  organically  bound 
phosphate  may  amount  to  from  1-4  per  cent  of  the  total  phosphorus 
excretion.  Little  is  known  with  regard  to  the  compounds  in  which  it 
occurs.  Possibly  some  glycerophosphoric  acid  may  occur  either  free 
or  as  lecithin. 

Gravimetric  Modification. — The  phosphorus  may  be  determined  somewhat 
more  accurately  by  substituting  a  gravimetric  procedure  for  the  above  titration. 
In  this  case  the  washed  phosphomolybdate  precipitate  is  dissolved  on  the  filter 
paper  with  ammonium  hydroxide  and  hot  water  to  make  a  volume  of  not  more  than 
100  c.c.  Nearly  neutralize  with  HC1,  cool,  and  add  about  10  c.c.  of  magnesia 
mixture  (see  Appendix)  from  a  burette.  Add  slowly  (about  i  drop  per  second) 
stirring  vigorously.  After  15  minutes  add  12  c.c.  of  ammonium  hydroxide 

1  Made  by  adding  5  c.c.  of  concentrated  HNO8  to  100  c.c.  of  the  ordinary  molybdate 
solution  (see  Reagents  and  Solutions,  page  638). 

2  It  is  better  to  use  a  special  filter  tube  of  about  i^  inches  diameter  (similar  to  a  Gooch 
filtering  tube)  in  which  is  placed  a  perforated  porcelain  plate  i3^  inches  in  diameter,  covered 
with  a  layer  of  asbestos  y%  inch  thick.     Filtration  is  carried  out  with  suction  and  is  very 
rapid.    Ordinary  Gooch  crucibles  lined  with  asbestos  may  also  be  used  but  are  not  so  satis- 
factory.   The  asbestos  used  should  be  specially  prepared  (see  Appendix).     For  a  good  dis- 
cussion of  the  details  of  procedure  and  sources  of  error  of  this  volumetric  method  see 

Hibbard:  /.  Ind.  Eng.  Chem.,  5,  998,  1913. 


572  PHYSIOLOGICAL   CHEMISTRY 

i 

solution  (sp.  gr.  0.90).  Let  stand  for  some  time  (two  hours  is  usually  enough) 
then  filter  and  wash  the  precipitate  with  2.5  per  cent  ammonia  until  practically 
free  from  chlorides.  Ignite  to  whiteness  or  to  a  grayish-white  ash  and  weigh. 
Multiply  the  weight  of  magnesium  pyrophosphate  thus  obtained  by  0.637  to  get 
the  weight  of  P2O5. 

Calculation. — Calculate  as  explained  above. 

Chlorides 

i.  Volhard-Arnold  Method.— Principle. — The  urine  is  acidified 
with  nitric  acid  and  the  chlorides  precipitated  with  a  measured  excess 
of  standard  silver  nitrate  solution.  The  silver  chloride  formed  is 
filtered  off  and  in  the  filtrate  the  excess  silver  nitrate  is  titrated 
back  with  standard  ammonium  thiocyanate  solution.  Ferric  am- 
monium sulphate  is  used  as  an  indicator.  A  red  color  due  to  the  forma- 
tion of  ferric  thiocyanate  indicates  that  an  excess  of  thiocyanate  is 
present  and  that  the  end  point  has  been  reached. 

Procedure. — Place  10  c.c.  of  urine  in  a  100  c.c.  volumetric  flask,  add  20-30 
drops  of  nitric  acid  (sp.  gr.  1.2)  and  2  c.c.  of  a  cold  saturated  solution  of  ferric 
alum.  If  necessary,  at  this  point  a  few  drops  of  8  per  cent  solution  of  potassium 
permanganate  may  be  added  to  dissipate  the  red  color.  Now  slowly  run  in  a 
known  volume  of  the  standard  silver  nitrate1  solution  (20  c.c.  is  ordinarily  used) 
in  order  to  precipitate  the  chlorine  and  insure  the  presence  of  an  excess  of  silver 
nitrate.  The  mixture  should  be  continually  shaken  during  the  addition  of  the 
standard  solution.  Allow  the  flask  to  stand  10  minutes,  then  fill  it  to  the  100 
c.c.  graduation  with  distilled  water  and  thoroughly  mix  the  contents.  Now 
filter  the  mixture  through  a  dry  filter  paper,  collect  50  c.c.  of  the  filtrate  and 
titrate  it  with  standardized  ammonium  thiocyanate  solution.2  The  first  per- 
manent tinge  of  red-brown  indicates  the  end  point.  Take  the  burette  reading 
and  compute  the  weight  of  sodium  chloride  in  the  10  c.c.  of  urine  used. 

Calculation. — The  number  of  cubic  centimeters  of  ammonium  thiocyanate 
solution  used  indicates  the  excess  of  standard  silver  nitrate  solution  in  the 
50  c.c.  of  filtrate  titrated.  Multiply  this  reading  by  2,  inasmuch  as  only  one- 
half  of  the  filtrate  was  employed,  and  subtract  this  product  from  the  number  of 
cubic  centimeters  of  silver  nitrate  (20  c.c.)  originally  used,  in  order  to  obtain  the 
actual  number  of  cubic  centimeters  of  silver  nitrate  utilized  in  the  precipitation 
of  the  chlorides  in  the  10  c.c.  of  urine  employed. 

1  Standard  silver  nitrate  solution  may  be  prepared  by  dissolving  29.042  grams  of  silver 
nitrate  in  i  liter  of  distilled  water.     Each  cubic  centimeter  of  this  solution  is  equivalent  to- 
o.oio  gram  of  sodium  chloride  or  to  0.006  gram  of  chlorine. 

2  This  solution  is  made  of  such  a  strength  that  i  c.c.  of  it  is  equal  to  i  c.c.  of  the  stand- 
ard silver  nitrate  solution  used.    To  prepare  the  solution  dissolve  13  grams  of  ammonium 
thiocyanate,  NH^SCN,  in  a  little  less  than  a  liter  of  water.    In  a  small  flask  place  20  c.c. 
of  the  standard  silver  nitrate  solution,  5  c.c.  of  the  ferric  alum  solution  and  4  c.c.  of  nitric 
acid  (sp.  gr.  1.2),' add  water  to  make  the  total  volume  100  c.c.  and  thoroughly  mix  the  con- 
tents of  the  flask.    Now  nfn  in  the  ammonium  thiocyanate  solution  from  a  burette  until  a 
permanent  red-brown  tinge  is  produced.    This  is  the  end-reaction  and  indicates  that  the 
last  trace  of  silver  nitrate  has  been  precipitated.    Take  the  burette  reading  and  calculate 
the  amount  of  water  necessary  to  use  in  diluting  the  ammonium  thiocyanate  in  order  that 
10  c»c,  of  this  solution  may  be  exactly  equal  to  10  c.c.  of  the  silver  nitrate  solution.    Make 
this  dilution  and  titrate  again  to  be  certain  that  the  solution  is  of  the  proper  strength. 


URINE  573 

To  obtain  the  weight  in  grams  of  the  sodium  chloride  in  the  10  c.c.  of  urine 
used,  multiply  the  number  of  cubic  centimeters  of  the  standard  silver  nitrate 
solution,  actually  utilized  in  the  precipitation,  by  o.oio.  If  it  is  desired  to  express 
the  result  in  percentage  of  sodium  chloride  move  the  decimal  point  one  place 
to  the  right. 

In  a  similar  manner  the  weight,  or  percentage  of  chlorine  may  be  computed 
using  the  factor  0.006  instead  of  o.oio. 

Calculate  the  quantity  of  sodium  chloride  and  chlorine  in  the  24-hour  urine 
specimen. 

Interpretation. — From  10-15  grams  of  chlorine,  expressed  as  sodium 
chloride,  are  excreted  per  day,  on  the  average,  by  normal  adults.  The 
amount  is,  however,  closely  dependent  upon  the  chloride  content  of 
the  food  ingested.  In  fasting,  the  chloride  excretion  falls  rapidly  to 
a  very  minimal  quantity.  On  high  water  ingestion  it  is  increased. 
In  pneumonia  and  certain  other  acute  infectious  diseases  the  excretion 
of  chlorides  may  be  markedly  diminished  particularly  during  the 
periods  in  which  exudates  are  forming.  In*  convalescence  and  with 
resolution  of  the  exudates  the  chlorine  excretion  rises  again.  A  de- 
crease has  also  been  noted  in  nephritis  associated  with  edema. 

2.  Volhard-Harvey  Method.1 — Principle. — This  procedure  differs 
from  the  Volhard- Arnold  method  in  that  the  excess  of  silver  nitrate 
is  titrated  directly  without  filtering  and  hence  in  the  presence  of  the 
silver  chloride.  The  procedure  is  thus  more  rapid  but  the  exact  end 
point  is  more  difficult  to  determine. 

jr  \ 

Procedure. — Introduce  5  c.c.  of  urine  into  a  small  porcelain  evaporating 
dish  or  casserole  and  dilute  with  about  20  c.c.  of  distilled  water.  Precipitate 
the  chlorides  by  the  addition  of  10  c.c.  of  standard  silver  nitrate  solution2  and 
add  2  c.c.  of  acidified  indicator.3  Now  run  in  a  standard  ammonium  thiocyanate 
solution4  from  a  burette  until  a  faint  red-brown  tint  is  visible  throughout  the 
mixture.  This  point  may  be  determined  readily  by  permitting  the  precipitate 
to  settle  somewhat.  Calculate  the  sodium  chloride  value  as  indicated  below. 

1  Harvey:  Archives  of  Internal  Medicine,  6,  12,  1910. 

2  See  p.  572. 

3  This  is  prepared  as  follows:  To  30  c.c.  of  distilled  water  add  70  c.c.  of  33  per  cent 
nitric  acid  (sp.  gr.  1.2)  and  dissolve  100  grams  of  crystalline  ferric  ammonium  sulphate  in 
this  dilute  acid  solution.    Filter  and  use  the  filtrate  which  is  a  saturated  solution  of  the  iron 
salt.     This  single  reagent  takes  the  place  of  the  nitric  acid  and  ferric  alum  as  used  in  Vol- 
hard-Arnold  method,  and  insures  the  use  of  the  proper  quantity  of  acid. 

4  This  is  a  solution  of  ammonium  thiocyanate  of  such  a  strength  that  2  c.c.  is  equivalent 
to  i  c.c.  of  the  silver  nitrate  solution.     First  make  a  concentrated  solution  by  dissolving  13 
grams  in  i  liter  of  water.     To  determine  the  requisite  dilution  to  make  such  a  solution  that 
2  c.c.  shall  be  equivalent  to  i  c.c.  of  the  silver  nitrate  solution  proceed  as  follows  introduce 
10  c.c.  of  the  silver  nitrate  solution  into  a  small  porcelain  evaporating  dish  or  casserole,  add 
30-50  c.c.  of  distilled  water,  2  c.c.  of  the  acid  indicator  and  titrate  as  described  above  with 
the  ammonium  thiocyanate  solution.    The  total  volume  of  the  concentrated  thiocyanate 
solution  excluding  that  used  in  this  titration  is  divided  by  the  burette  reading  and  the 
result  multiplied  by  the  difference  between  this  burette  reading  and  20  c.c.     This  will  give 
the  volume  of  distilled  water  wjiich  must  be  added  to  the  concentrated  thiocyanate  solu- 
tion to  render  2  c.c.  equivalent  to  i  c.c.  of  the  silver  nitrate  solution. 


574  PHYSIOLOGICAL   CHEMISTRY 

(If  a  red  tint  is  produced  when  the  first  drop  of  thiocyanate  is  added  an  addi- 
tional 10  c.c.  of  the  standard  silver  nitrate  solution  must  be  introduced.  The 
titration  should  then  proceed  as  above  described  and  proper  allowance  made  in 
the  calculation  for  the  extra  volume  of  silver  nitrate  employed.) 

Calculation. — Since  2  c.c.  of  the  ammonium  thiocyanate  solution  is  equivalent 
to  i  c.c.  of  the  silver  nitrate  solution,  divide  the  burette  reading  by  2  and  sub- 
tract the  quotient  from  10  c.c.,  the  quantity  of  silver  nitrate  solution  taken. 
This  value  is  the  number  of  cubic  centimeters  of  silver  nitrate  solution  actually 
used  in  the  precipitation  of  the  chlorides.  As  i  c.c.  of  the  silver  nitrate  solution 
is  equivalent  to  o.oi  gram  of  sodium  chloride,  the  number  of  cubic  centimeters 
of  silver  nitrate  solution  used  multiplied  by  o.oi  gram  will  give  the  weight  of 
sodium  chloride  in  the  5  c.c.  portion  of  urine  used.  The  weight  of  chlorine  may 
be  computed  by  using  the  factor  0.006  instead  of  o.oi. 

Calculate  the  weight  of  sodium  chloride  and  chlorine  in  the  24-hour  urine 
specimen. 

A  "short  cut"  method  of  calculating  the  24-hour  output  of  sodium  chloride 
consists  in  subtracting  the  burette  reading  from  20  c.c.,  multiplying  this  value 
by  the  total  urine  volume  and  pointing  off  three  places. 

Interpretation. — See  above. 

Calcium  and  Magnesium 

McCrudden's  Methods.1— -Principle. — Urine  contains  magnesium, 
phosphates  and  a  small  amount  of  iron,  each  of  which  will  interfere 
with  the  accurate  determination  of  its  calcium  content  if  proper  con- 
ditions of  acidity  are  not  maintained  during  the  precipitation.  In  the 
following  method  the  proper  acidity  is  attained  through  the  use  of 
sodium  acetate  and  hydrochloric  acid,  and  this  with  slow  addition  of 
the  ammonium  oxalate  reduces  the  danger  of  occlusion  of  magnesium 
oxalate,  calcium  phosphate,  or  ferric  phosphate  in  the  calcium  oxalate 
precipitate. 

The  calcium  oxalate  precipitate  is  either  ignited  and  weighed  as 
CaO  or  determined  volumetrically  by  titration  with  potassium  per- 
manganate. Magnesium  is  determined  in  the  filtrate  from  the  calcium 
determination  after  destruction  of  the  organic  matter.  It  is  determined 
in  the  usual  way  by  ignition  of  the  magnesium  ammonium  phosphate 
precipitate  and  weighing  as  the  pyrophosphate. 

Lyman  has  suggested  a  nephelometric  method  for  the  determination 
of  calcium  in  urine  and  feces.2 

Procedure  for  Calcium.— If  the  urine  is  alkaline  make  it  neutral  or  slightly 
acid  and  filter.  Take  200  c.c.  of  the  filtered  urine  for  analysis.  If  it  is  only 
faintly  acid  to  litmus  paper  add  10  drops  of  concentrated  hydrochloric  acid  (sp. 
gr.  i  .20) .  If  the  urine  is  strongly  acid  it  may  be  made  just  alkaline  with  ammonia 

1  McCrudden:  Jour.  Biol.  Chem.,  7,  83,  1910;  10,  187,  1911. 

2  Lyman:  Jour.  Biol.  Chem.,  21,  551,  1915. 


URINE  575 

and  then  just  acid  with  hydrochloric  acid  after  which  the  10  drops  of  concentrated 
hydrochloric  acid  are  added.  Then  add  10  c.c.  of  2.5  per  cent  oxalic  acid.  Run 
in  slowly  with  stirring  8  c.c.  of  20  per  cent  sodium  acetate.  Allow  to  stand  over 
night  at  room  temperature  or  shake  vigorously  for  ten  minutes.  Filter  off  the 
precipitate  of  calcium  oxalate  on  a  small  paper  and  wash  free  from  chlorides 
with  0.5  per  cent  ammonium  oxalate  solution.  The  precipitate  may  then  be 
dried,  ignited  to  constant  weight  and  weighed  as  calcium  oxide  or  it  may  be 
manipulated  volumetrically  as  described  below. 

Volumetric  Procedure.— If  free  from  uric  acid  the  calcium  oxalate  precipitate 
may  be  washed  three  times  with  distilled  water,  filling  the  filter  about  two- 
thirds  full  and  allowing  it  to  drain  completely  before  adding  more.  A  hole  is 
made  in  the  paper  and  the  calcium  oxalate  washed  into  the  flask.  The  volume 
of  the  fluid  is  brought  up  to  about  50  c.c.  and  10  c.c.  of  concentrated  sulphuric 
acid  added.  Titrate  with  standard  potassium  permanganate  solution  to  a  pink 
color  which  endures  for  at  least  a  minute. 

Calculation. — One  c.c.  of  N/io  permanganate  solution  is  equivalent  to  2.8 
mg.  of  CaO.  Calculate  the  daily  output  of  calcium  expressed  as  CaO. 

Interpretation. — The  average  urinary  excretion  of  calcium  by  normal 
adults  lies  between  o.i  to  0.4  gram  (expressed  as  CaO)  per  day.  It  is 
dependent  very  largely  upon  the  amount  of  calcium  in  the  diet.  From 
10  to  40  per  cent  of  the  ingested  calcium  ordinarily  is  excreted  by  this 
channel,  the  greater  part  being  eliminated  by  the  feces.  The  pro- 
portion is  dependent  particularly  on  the  amount  of  calcium  in  the  food. 
If  the  calcium  ingestion  is  very  high  the  per  cent  of  the  total  excretion 
taking  place  by  way  of  the  kidneys  will  be  low,  and  vice  versa.  As  ex- 
cretion takes  place  by  way  of  the  intestine  as  well  as  by  the  kidneys  no 
conclusions  can  be  drawn  from  urinary  analyses  alone.  The  excretion 
of  calcium  may  be  greatly  increased  in  certain  bone  disorders  as  osteo- 
malacia.  In  others  as  in  rickets  the  urinary  excretion  may  be  very 
low.  , 

Procedure  of  Magnesium. — Transfer  the  filtrate  from  the  determination 
of  calcium  as  above  to  a  porcelain  dish,  add  about  20  c.c.  of  concentrated  nitric 
acid  and  evaporate  to  dryness.  Heat  the  residue  over  a  free  flame  until  the 
ammonium  salts  are  destroyed  and  the  residue  fuses.  After  cooling  take  the 
residue  up  with  water  and  a  little  hydrochloric  acid  and  filter  if  necessary. 
Dilute  to  about  80  c.c.,  nearly  neutralize  with  ammonia  and  cool.  Add  a  slight 
excess  of  sodium  acid  phosphate  and  then  ammonia  drop  by  drop  with  constant 
stirring  until  the  solution  is  alkaline  and  then  add  enough  more  slowly  with 
constant  stirring  to  make  the  solution  contain  one -fourth  its  bulk  of  dilute 
ammonia  (sp.  gr.  0.96).  Allow  to  stand  over  night.  Filter  and  wash  free  from 
chlorides  with  alcoholic  ammonia  solution  (i  part  alcohol,  i  part  dilute  ammonia, 
3  parts  water).  The  precipitate  with  filter  paper  is  incinerated  slowly  and  care- 
fully with  good  supply  of  air  to  prevent  reduction,  in  the  usual  manner,  and  ignited 
and  weighed  as  the  pyrophosphate. 

Calculation. — To  obtain  the  weight  of  MgO  multiply  the  weight  of  magnesium 
pyrophosphate  by  0.3624. 


576  PHYSIOLOGICAL  CHEMISTRY 

Interpretation. — The  daily  excretion  of  magnesium  by  way  of  the 
urine  usually  amounts  to  between  o.i  and  0.3  gram  (expressed  as  MgO). 
The  amount  depends  mainly  upon  the  diet.  Usually  50  per  cent  or 
more  of  the  excreted  magnesium  is  eliminated  by  the  kidneys,  the  re- 
mainder passing  out  in  the  feces.  The  proportion  varies,  however,  and 
it  is  impossible  to  draw  any  conclusions  from  the  urinary  output  alone. 
There  may  be  a  retention  of  magnesium  in  certain  bone  disorders  ac- 
companying a  loss  of  calcium;  in  osteomalacia  for  example.  Thus  the 
excretions  of  calcium  and  magnesium  do  not  necessarily  run  parallel. 

Determination  of  Calcium  in  Ash  of  Foods  or  Feces. — Ignite  the  material  in  a 
crucible  to  a  white  ash  and  dissolve  the  ash  with  the  aid  of  a  little  hydrochloric  acid. 
Bring  the  volume  of  the  ash  solution  to  75-150  c.c.  Make  just  alkaline  with  strong 
ammonia  added  drop  by  drop  (using  litmus  paper  or  alizarin  as  an  indicator).  Add 
concentrated  HC1  drop  by  drop  until  just  acid  to  litmus.  Then  add  10  drops  of 
concentrated  HC1  (sp.  gr.  1.20),  and  10  c.c.  of  2.5  per  cent  oxalic  acid.  Either 
of  two  procedures  may  then  be  followed,  (a)  The  solution  is  boiled  until  the  pre- 
cipitated calcium  oxalate  is  coarsely  crystalline,  and  then  an  excess  of  3  per  cent 
ammonium  oxalate  is  slowly  added  to  the  boiling  solution  and  the  boiling  continued 
until  the  precipitate  is  coarsely  crystalline.  (If  but  little  calcium  is  present  nothing 
will  precipitate  at  this  point  and  it  is  not  necessary  to  add  oxalate.)  Or  (6)  the 
flask  closed  with  a  rubber  stopper  is  shaken  vigorously  for  ten  minutes.  An  excess 
of  3  per  cent  ammonium  oxalate  is  then  added.  Cool  to  room  temperature.  Add 
8  c.c.  of  20  per  cent  sodium  acetate  solution.  (In  case  of  ash  of  feces  add  15  c.c.) 
The  solution  may  either  be  (a)  allowed  to  stand  over  night  or  (b)  stoppered  and 
vigorously  shaken  for  ten  minutes.  The  calcium  oxalate  is  filtered  off  on  a  small 
ash^free  paper  and  washed  free  from  chlorides  with  0.5  per  cent  ammonium  oxalate 
solution.  Either  of  two  procedures  may  next  be  followed,  (a)  The  precipitate 
and  filter  are  dried,  burned  in  a  platinum  or  porcelain  crucible  to  constant  weight  as 
CaO.  (b)  The  precipitate  is  washed  three  times  with  cold  distilled  water,  as  given 
under  the  method  for  urine  and  the  oxalate  titrated  with  potassium  permanganate. 
Magnesium  is  determined  in  the  filtrate  from  calcium  just  as  given  above. 

Sodium  and  Potassium 

Determination  of  Combined  Sodium  and  Potassium. — From  50  to  100  c.c.  of 
urine,  depending  upon  the  specific  gravity,  are  oxidized  in  a  Kjeldahl  flask  with 
nitric  and  sulphuric  acids  as  in  the  Neumann  procedure  for  total  phosphorus  (see 
page  570).  To  remove  the  sulphuric  acid  as  completely  as  possible  transfer  with 
the  aid  of  a  little  water  to  a  platinum  dish  and  evaporate  to  dryness  over  &  free 
flame.  (The  alkalies  are  in  the  form  of  sulphate  and  do  not  volatilize.)  Dissolve 
the  residue  in  hot  water  with  the  aid  of  a  little  dilute  hydrochloric  acid.  Heat  to 
boiling  and  add  barium  chloride  solution  until  no  more  precipitate  forms.  While 
still  hot  add  an  excess  of  ammonia  and  ammonium  carbonate.  The  barium  chlo- 
ride precipitates  the  sulphates  and  part  of  the  phosphates:  the  ammonia  in  the 
presence  of  excess  barium  precipitates  the  rest  of  the  phosphates,  and  the  carbonate 
precipitates  the  calcium  and  most  of  the  magnesium,  as  well  as  the  excess  barium. 
Filter  and  wash  the  precipitate  well  with  hot  water  containing  a  few  drops  of  am- 


URINE  577 

monia.  Evaporate  filtrate  and  washings  to  dryness  and  heat  the  residue  to  dull 
redness  for  a  moment.  Redissolve  in  water  and  treat  again  with  ammonia  and 
ammonium  carbonate  to  remove  any  remaining  alkaline  earth  metals.  Filter  and 
wash  as  before.  Transfer  filtrate  and  washings  to  a  weighed  platinum-  dish,  add  a 
few  drops  of  hydrochloric  acid  and  evaporate  to  dryness.  Heat  the  residue  gently 
to  remove  ammonium  salts  and  then  to  dull  redness  for  a  moment.  Desiccate 
and  weigh.  Reheat  to  constant  weight  which  represents  the  combined  chlorides 
of  sodium  and  potassium.  The  reagents  used  in  trie  determination  must  be  tested 
and  found  free  from  alkali  metals  or  a  correction  made  for  the  alkali  metals  present 
in  the  reagents  used.  The  sodium  is  determined  by  difference  after  potassium  has 
been  estimated  by  the  method  given  below. 

Potassium. — Dissolve  the  alkali  chlorides  from  the  preceding  determination  in  a 
little  water  and  add  a  slight  excess  of  10  per  cent  platinic  chloride  over  that  neces- 
sary to  precipitate  all  of  the  alkali  present  calculated  as  sodium  chloride  (about  17 
c.c.  being  required  for  each  gram  of  sodium  chloride).  Evaporate  to  a  syrupy  con- 
sistency on  the  water-bath  and  add  about  50  c.c.  of  80  per  cent  alcohol.  Stir 
occasionally  for  a  few  minutes.  This  operation  must  be  carried  out  in  the  absence  of 
ammonia  vapors.  Filter  through  a  weighed  Gooch  crucible,  washing  the  precipi- 
tate with  80  per  cent  alcohol  first  thoroughly  by  decantation  and  then  on  the  filter, 
for  some  time  after  the  filtrate  is  colorless.  Dry  at  iio-ii5°C.  and  weigh. 

Calculation. — Multiply  the  weight  of  potassium  platinic  chloride  by  0.1941  to 
obtain  the  amount  of  K2O  present.  Express  as  KC1  by  using  instead  of  this  factor 
the  factor  0.307 12.  Subtract  from  the  weight  of  total  alkali  chlorides  as  determined 
in  the  preceding  method,  the  weight  of  potassium  chloride  as  calculated  and  obtain 
the  amount  of  sodium  chloride  present. 

Interpretation. — The  average  alkali  excretion  of  an  adult  on  a  mixed  diet  is  about 
2-3  grams  of  potassium  expressed  as  K20  and  4-6  grams  of  sodium  expressed  as 
NasO.  The  ratio  of  Na  to  K  is  thus  about  5:3.  Both  the  ratio  and  the  absolute 
amounts  of  these  elements  excreted  are,  however,  largely  dependent  upon  the  salt 
content  of  the  diet.  Because  of  the  non-ingestion  of  sodium  chloride  and  the 
accompanying  destruction  of  potassium-containing  body  tissues,  the  urine  during 
fasting  contains  more  potassium  than  sodium  salts.  The  excretion  of  the  bases, 
particularly  K,  may  be  increased  in  fevers  and. in  acidosis. 

Iron 

Method  of  Wolter.1 — Principle. — The  urine  is  ashed,  the  ash  dissolved,  and  the 
iron  present  oxidized  to  the  ferric  form  by  means  of  hydrogen  peroxide.  The  iron  is 
then  determined  iodometrically. 

Procedure. — The  24-hour  specimen  of  urine  is  treated  with  30  c.c.  of  concen- 
trated iron-free  nitric  acid  and  then  evaporated  to  low  volume  in  a  large  evaporating 
dish  on  the  water-bath.  Transfer  to  a  small  evaporating  dish.  Heat  to  dryness  on 
the  sand  bath  and  then  char,  using  a  small  flame.  Transfer  the  charred  mass  by 
means  of  a  glass  spatula  to  a  crucible.  The  remaining  material  in  the  evaporating 
dish  is  transferred  with  the  aid  of  a  little  hot  water  and  a  rubber  "policeman"  to  a 
second  crucible.  Evaporate  to  dryness  on  the  water-bath  and  then  ash  the  material 
in^both  crucibles.  Dissolve  the  ash  in  about  30  c.c.  of  iron-free  hydrochloric  acid, 
transfer  to  an  Erlenmeyer  flask,  add  2  c.c.  of  hydrogen  peroxide  and  boil  for  three- 

1  Wolter:  Bioch.  Zeit.,  24,  108,  1910. 
37 


578  PHYSIOLOGICAL  CHEMISTRY 

quarters  of  an  hour.  After  cooling,  2  grams  of  potassium  iodide  and  a  few  drops  of 
fresh  starch  paste  are  added.  The  liberated  iodine  is  titrated  with  N/ioo  thiosul- 
phate  solution.  Controls  should  be  run  on  reagents.  A  correction  of  0.32  mg.  is 
usually  necessary  for  the  undecomposed  hydrogen  peroxide.  The  thiosulphate  solu- 
tion is  made  up  as  needed  from  an  N/io  stock  solution  by  dilution.  It  is  standard- 
ized against  an  iron  solution  containing  2  mg.  of  iron  in  10  c.c.  The  number  of 
cubic  centimeters  of  thiosulphate  used  in  titration  of  the  iodine  set  free  from  the 
ash  solution  is  multiplied  by  the  iron  equivalent  of  i  c.c.  of  the  thiosulphate  (about 
0.2  mg.)  to  obtain  the  total  amount  of  iron  in  the  24-hour  specimen  of  urine.  From 
1-5  mg.  of  iron  are  usually  excreted  per  day. 


CHAPTER   XXVIII 
METABOLISM 

Metabolism  is  a  part  of  that  complex  series  of  processes  grouped 
together  under  the  head  of  Nutrition.  It  embraces  a  consideration 
of  those  changes  taking  place  in  the  body  other  than  those  customarily 
classified  as  secretion,  digestion,  excretion,  etc.  Metabolism  may  be  de- 
fined as  all  chemical  and  physical  changes  which  occur  in  living  matter 
and  which  constitute  the  basis  of  the  material  phenomena  of  life.  This 
conception  of  metabolism  holds  for  the  simple  individual  cell  of  the 
amoeba  as  well  as  for  the  complex  mechanism  of  the  human  body.  There 
are  two  types  of  metabolism,  one  constructive,  the  other  destructive. 
The  constructive  metabolism  is  termed  anabolism;  the  destructive 
metabolism  is  termed  catabolism. 
Thus: 

{Anabolism  (constructive  metabolism). 
I  Catabolism  (destructive  metabolism). 

In  general  we  may  say  that  the  main  bulk  of  the  food-stuffs  of  the  diet 
i.e.,  protein,  fat  and  carbohydrate,  is  transformed  in  the  gastro-in- 
testinal  tract  and  that  the  end-products  of  this  transformation  are 
carried  to  the  cells  of  the  body  and  there  built  up  by  anabolic  (synthetic) 
processes  into  cell  structure  or  stored  as  a  reserve  to  be  used  as  required. 
All  living  cells  undergo  wear  and  tear  in  the  course  of  their  life  cycje. 
By  catabolic  (cleavage)  processes  therefore  a  portion  of  the  living  cell 
substance  or  of  the  stored  material  is  reduced  to  simpler  fragments  and 
these  are  eliminated  from  the  body  after  having  yielded  the  bulk  of 
their  energy  in  the  form  of  heat  or  mechanical  work.  It  is  apparent r 
therefore,  that  the  chemical  side  of  metabolism  is  closely  associated 
with  the  physical  side.  Each  of  the  three  types  of  food-stuffs  (protein, 
fat  and  carbohydrate)  is  concerned  with  the  upkeep  of  the  tissues  and 
with  the  liberation  of  energy.  It  is  true,  however,  that  the  main 
burden  of  the  upkeep  falls  upon  the  proteins  whereas  the  combustion  of 
fats  and  carbohydrates  yields  the  major  portion  of  the  required  energy. 
The  above  facts  are  embraced  in  the  following  scheme: 

579 


580  PHYSIOLOGICAL   CHEMISTRY 

THE  CELL 


PROTEIN,  FAT,       \  ^^  ^^        END-PRODUCTS 

CARBOHYDRATE  > 


COMBUSTION 

Without  doubt  both  anabolic  and  catabolic  processes  are  going  on  in- 
cessantly within  every  individual  living  cell.  At  one  time  the  anabolic 
phase  will  be  more  prominent;  at  another  the  catabolic  activity  will  be 
in  the  ascendency.  It  should  also  be  borne  in  mind  that  metabolism 
implies  a  transformation  of  energy  as  well  as  an  exchange  of  materials. 

For  further  brief  discussions  of  certain  phases  of  metabolism  see 
the  following  experiments.  A  detailed  discussion  being  out  of  place 
in  this  volume,  the  reader  is  referred  to  the  following  books: 

(1)  Taylor's  "Digestion  and  Metabolism,"  Lea  and  Febiger. 

(2)  Sherman's  "Chemistry  of  Food  and  Nutrition,"  Macmillan. 

(3)  Osier  &  McCrae's  "Modern  Medicine,"  Vol.  II,  Second  Edi- 
tion, Lea  and  Febiger.     The  author's  section  on  "General  Considera- 
tions of  Metabolism,"  pages  549-673. 

(4)  Lusk's  "The  Science  of  Nutrition,"  Saunders. 

METABOLISM  EXPERIMENTS 

i.  Influence  of  Dietary  Deficiencies 

Introduction. — Approximate  weight  equilibrium  is  a  standard  condition  for 
the  majority  of  adult  men  and  women.  The  child,  on  the  contrary,  must  show 
a  continuous  gain  in  body  weight  in  order  to  be  adjudged  normal.  All  other 
things  being  equal,  the  child  who  receives  an~  adequate  diet  will  show  normal 
growth  gains,  whereas  the  child  who  receives  a  deficient  diet  will  fail  to  grow  or 
will  grow  at  an  abnormally  slow  rate.  The  character  and  extent  of  the  dietary 
deficiency  will  regulate  the  character  and  extent  of  the  gains  or  losses  in  body 
weight. 

In  order  that  a  diet  may  be  adequate  for  growth,  it  must  contain  at  least 
seven  factors  as  follows : 

1.  "Fat-Soluble  A"  Vitamine. 

2.  "Water-Soluble  B»  Vitamine. 

3.  "  Water-Soluble  C"  Vitamine. 

4.  Protein,  proper  in  kind  and  amount. 

5.  Energy  furnished  by  fats  and  carbohydrates. 

6.  Inorganic  matter,  proper  in  kind  and  amount. 

7.  Water, 

In  order  that  the  above  dietary  factors  shall  function  most  satisfactorily, 
sufficient  roughage  should  be  included  to  obviate  constipation  and  insure  the 
evacuation  of  normal  stools. 


METABOLISM  5  81 

By  the  use  of  the  proper  experimental  animals,  the  influence  of  a  diet  deficient 
in  any  one  of  the  seven  essential  dietary  factors  may  be  readily  demonstrated. 
Typical  dietary  demonstrations  of  this  character  are  outlined  on  the  following 
pages. 

i.  Influence  of  Vitamine  Deficiency. — As  a  result  of  the  work  of  different 
experimenters,  certain  "accessory  food  substances,"  "growth-promoting 
substances,"  or  vitamines,  as  they  are  variously  termed,  have  been  shown  to  be 
of  great  importance  in  nutrition.  The  exact  character  of  these  substances  has 
not  been  established.  These  are  two  distinct  growth-promoting  vitamines,  one 
soluble  in  fats  and  called  "Fat-Soluble  A,"  the  other  soluble  in  water  and 
called  "Water-Soluble  B."  The  third  accessory  food  substance  is  an  anti- 
scorbutic vitamine  called  "  Water-Soluble  C."  These  three  substances  have  a 
rather  wide  distribution  as  shown  by  the  following  table : — 

DISTRIBUTION  OF  THE  THREE  VITAMINES1 


Fat-soluble  A 

Water-soluble  B 

Water-soluble  C 

Butter 

Yeast 

Lemon  juice 

Cream 

Milk  (whole  or  skim) 

Orange  juice 

Milk  (whole) 

Eggs 

Lime  juice 

Eggs  (Yolk) 

Rice  (unpolished) 

Cabbage  (fresh) 

Beef  fat 

Peanuts 

Tomatoes 

Mutton  fat 

Pancreas 

Milk  (whole  or  skim) 

Cod  liver  oil 

Liver                                           Carrots  (raw) 

Liver 

Kidney                                        Beans  (raw  scarlet  runner) 

Kidney 

Heart                                          Raspberries 

Heart 

Brain                                           Apples 

Brain 

Beans  (kidney)         •                 Potatoes 

Pancreas 

Corn     (kernels,     germ,     andjLean    meat    (beef,    mutton, 

Spinach 

and  bran)                                    etc.) 

Potatoes 

Oat  (kernel)                               [Liver 

Cabbage 

Wheat    (kernel,    germ,    and  Germinated  cereals 

Lettuce 

bran)                                       i  Germinated  legumes 

Carrots  • 

Lean    meat    (beef,    mutton, 

. 

Alfalfa 

etc.) 

Clover 

Oranges 

Timothy 

Lemons 

Corn  (kernel  and  germ) 

Pears 

Oat  (kernel) 

Grapefruit 

Wheat  (kernel  and  germ) 

Prunes 

Nuts 

Bananas 

Tomatoes 

"i 

important  vitamine  references  follow: 
Funk,  Casimir:  Journal  of  Physiology,  43,  395,  1911. 
Hopkins,  H.  Gowland:  Journal  of  Physiology,  44,  425,  1912. 
McCollum,  E.  V.,  and  Davis,  M.:  Jour.  Biol.  Chem.,  15,  167,  1913. 
Osborne,  Thomas  B.,  and  Mendel,  Lafayette  B.:  Jour.  Biol.  Chem.,  15,  311,  1913; 

24,  37,  1916  (other  references  cited  here);  32,  309,  1917;  34,  i7>  1918. 
McCollum,  E.  V.,  and  Simmonds,  N.:  Jour.  Biol.  Chem.,  33,  303,  1918. 
McCollum,  E.  V.,  Simmonds,  N.,  and  Parsons,  H.  T.:  Jour.  Biol.  Chem.,  33,  411,  1918. 
Osborne,  Thomas  B.,  and  Mendel,  Lafayette  B.:  Jour.  Biol.  Chem.,  35,  19,  1918. 


582  PHYSIOLOGICAL  CHEMISTRY 

The  influence  of  the  "Water-Soluble  B,"  vitamine  upon  growth  may  be 
shown  by  the  following  experiment. 

Demonstration  on  "Water  Soluble  B." — Take  two  white  rats  from  one  to 


Dutcher,  R.  Adams:  Jour.  Biol.  Chem.,  36,  63,  1918. 

Givens,  Maurice  H.,  and  Cohen,  Barnett:  Jour.  Biol.  Chem.,  36,  127,  1918. 

Sugiura,  Kanematsu,  and  Benedict,  Stanley  R.:  Jour.  Biol.  Chem.,  36,  171,  1918. 

Sugiura,  Kanematsu:  Jour.  Biol.  Chem.,  36,  191,  1918. 

McCollum,  E.  V.,  Simmonds,  N.,  and  Parsons,  H.  T.:  Jour.  Biol.  Chem.,  36,  197,  1918. 

Dutcher,  R.  Adams,  and  Collatz,  Ferdinand  A.:  Jour.  Biol.  Chem.,  36,  547,  1918. 

Dutcher,  R.  Adams:  Jour.  Biol.  Chem.,  36,  551,  1918. 

''Report  of  British  Medical  Research  Committee."  Special  Report  Series,  No.  38, 

London,  1919.     Includes  bibliography  up  to  1919. 

Osborne,  Thomas  B.,  and  Mendel,  Lafayette,  B.:  Jour.  Biol.  Chem.,  37,  187,  1919. 
Daniels,  Amy  L.,  and  McClurg,  Nelle  I.:  Jour.  Biol.  Chem.,  37,  201,  1919. 
Osborne,  Thomas  B.,  Mendel,  Lafayette  B.,  and  Ferry,  Edna  L.:  Jour.  Biol.  Chem., 

37,  223,  1919. 

Givens,  Maurice  H.,  and  McClugage,  Harry  B.:  Jour.  Biol.  Chem.,  37,  253,  1919. 
Hess,  Alfred  F.,  and  Unger,  Lester  J.:  Jour.  Biol.  Chem.,  38,  293,  1919.. 
Hart,  E.  B.,  Steenbock,  H.,  and  Smith,  D.  W.:  Jour.  Biol.  Chem.,  38,  305,  1919. 
Emmett,  A.  D.,  and  Luros,  G.  O.:  Jour.  Biol.  Chem.,  38,  441,  1919. 
Williams,  Roger  J. :  Jour.  Biol.  Chem.,  38,  465,  1919. 

Osborne,  Thomas  B.,  and  Mendel,  Lafayette  B.:  Jour.  Biol.  Chem.,  39,  29,  1919. 
Osborne,  Thomas  B.,  Wakeman,  Alfred  J.,  and  Ferry,  Edna  L.:  Jour.  Biol.  Chem., 

39,  35,  1919. 

Dutcher,  R.  Adams:  Jour.  Biol.  Chem.,  39,  63,  1919. 

Osborne,  Thomas  B.,  and  Wakeman,  Alfred  J.:  Jour.  Biol.  Chem.,  40,  383,  1919. 
Mitchell,  H.  H.:  Jour.  Biol.  Chem.,  40,  399,  1919. 

Sugiura,  Kanematsu,  and  Benedict,  Stanley  R.:  Jour.  Biol.  Chem.,  40,  449,  1919. 
Steenbock,  H.,  and  Gross,  E.  G. :  Jour.  Biol.  Chem.,  40,  501,  1919. 
Hawk,  Philip  B.,  Fishback,  Hamilton  R.,  and  Bergeim,  Olaf:  Am.  Jour.  PhysioL, 

48,  2ii,  1919. 
Hawk,  Philip  B.,  Smith,   Clarence  A.,  and  Holder,  Ralph  C.:  Am.  Jour.  PhysioL, 

48,  199,  1919. 

Steenbock,  H.,  and  Boutwell,  P.  W.:  Jour.  Biol.  Chem.,  41,  81,  1920. 
Steenbock,  H.,  and  Gross,  E.  G.:  Jour.  Biol.  Chem.,  41,  149,  1920. 
Osborne,  Thomas  B.,  and  Mendel,  Lafayette  B.:  Jour.  Biol.  Chem.,  41,  515,  1920. 
Osborne,  Thomas  B.,  and  Mendel,  Lafayette  B.:  Jour.  Biol.  Chem.,  41,  549,  1920. 
Steenbock,  H.  and  Boutwell  P.  W.,  Jour.  Biol.  Chem.,  42,  131,  1920. 
Myers,  C.  N.,  and  Voegtlin,  Carl:  Jour.  Biol  Chm.,  42,  199,  1920. 
Williams,  Roger  J.:  Jour.  Biol.  Chem.,  42,  259,  1920 
Dutcher,  R.  Adams,  Pierson,  Edith  M.,  and  Biester,  Alice:  Jour.  Biol.  Chem.,  42,  301, 

1920. 

Daniels,  Amy  L.,  and  Loughlin,  Rosemary:  Jour.  Biol.,  Chem.,  42,  359,  1920. 
Hart,  E.  B.,  Steenbock,  H.,  and  Ellis,  N.  R.:  Jour.  Biol.  Chem.,  42,  383,  1920. 
Osborne,  Thomas  B.,  and  Mendel,  Lafayette  B.:  Jour.  Biol.  Chem..,  42,  465,  1920. 
Givens,  Maurice  H.,  and  McClugage,  Harry  B.:  Jour.  Biol.  Chem.,  42,  491,  1920. 
Cajori,  F.  A.:  Jour.  Biol.  Chem.,  43,  583,  1920. 

Souza,  Geraldo  de  Paula,  and  McCollum,  E.  V.:  Jour.  Biol.  Chem.,  44,  113,  1920. 
•Miller,  Elizabeth  W.:  Jour.  Biol.  Chem.,  44,  159,  1920. 
Whipple,  Bertha  K,:  Jour.  Biol.  Chem.,  44,  175,  1920. 
Karr,  Walter  G.:  Jour.  Biol.  Chem.,  44,  255,  1920     . 
Karr,  Walter  G. :  Jour.  Biol.  Chem.,  44,  277,  1920. 

Daniels,  Amy  L.,  and  Loughlin,  Rosemary:  Jour.  Biol.  Chem.,  44,  381,  1920. 
Funk,  Casimir,  and  Dubin,  Harry  E.:  Jour.  Biol.  Chem.,  44,  487,  1920. 
McCollum,  E.  V.,  and  Parsons,  Helen  T.:  Jour.  Biol.  Chem.,  44,  603,  1920. 
Dutcher,  R.  A.,  Eckles,  C.  H.,  Dahle,  C.  D.,  Mead,  S.  W.,  and  Schaefer,  O.  G.:  Jour. 

Biol.  Chem.,  45,  119,  1920. 

Osborne,  T.  B.,  and  Mendel  L.  B.,  Jour.  Biol.  Chem.,  45,  145,  1920. 
Hess,  Alfred  F.,  Unger,  L.  J.,  and  Supplee,  G.  C.:  Jour.  Biol.  Chem.,  45,  229,  1920. 
Osborne,  Thomas  B.,  and  Leavenworth,  Charles  S.:  Jour.  Biol.  Chem.,  45,  423,  1921. 
Nelson,  V.  E.,  Fulmer,  Ellis  L,  and  Cessna,  Ruth:  Jour.  Biol.  Chem.,  46,  77,  1921. 
Williams,  Roger  J.:  Jour.  Biol.  Chem.,  46,  113,  1921. 

Hart  E.  B.,  Steenbock,  H.,  and  Ellis  N.  R.,  Jour.  Biol.  Chem.,  46,  309,  1921. 
Sherman,  H.  C.,  Rouse,  M.  E.,  Allen,  B.,  and  Woods,  E.:  Jour.  Biol.  Chem.,  46,  503, 

1921. 


METABOLISM 


583 


two  months  old  and  weighing  30-60  grams  each  and  feed  them  daily  upon  a  diet 
adequate  from  every  standpoint.1  Such  a  diet  may  consist  of  casein  (20  per 
cent),  butter  fat  (15  per  cent),  starch  (56  per  cent),  salt  mixture  (4  per  cent2) 
and  yeast  (5  per  cent).3  The  yeast  furnishes  the  "Water  Soluble  B"  whereas 
the  "  Fat  Soluble  A  "  is  furnished  by  the  butter  fat.  On  the  above  diet  the  rats 
will  show  normal  growth  (see  Fig.  170)  approximately  doubling  their  weight  in 


Growth  in  body  weight    Albino  Rat 


FIG.  170.— NORMAL  GROWTH  CURVES  or  ALBINO  RATS. 
(After  Donaldson.) 

two  weeks.4  The  animals  should  be  weighed  at  intervals  of  one  week.  At 
the  end  of  two  weeks  eliminate  the  yeast  from  the  diet  leaving  the  diet  un- 
changed in  all  other  respects.  The  diet  now  lacks  the  water  soluble  vitamine 
and  the  animals  will  not  only  fail  to  grow  but  will  show  an  actual  loss  of  weight 
A  period  of  two  weeks  on  this  diet  will  be  sufficient  to  demonstrate  this  fact 

*A  very  satisfactory  form  of  cage  in  use  by  Osborne  and  Mendel  may  be  obtained  from 
the  A.  B.  Hendryx  Co.,  New  Haven,  Conn.     This  cage  is  shown  in  Fig.  180. 

2 The  salt  mixture  should  have  the  following  composition: 
CaCO3 134-8      gm.    K2CO3 141-3      gm.    H2SO4 9.2        gm. 


MgC03  . . 
Na2CO3 . . 
KL. 


24 . 2      gm. 

34  •  2      gm. 

0.020  gm. 


H3PO4 103.2 

HC1 53-4       gm. 

MnSO4 0.079  gm. 


gm.    Citric  acid  -f-  H2O . .  1 1 1 .  i        gm. 
Fe  citrate  + 1  >iH2O    6.34      gm. 

NaF o .  248    gm' 

K2A12(SO4)2 0.0245  gm. 

3  Fleischmann's   Compressed  Yeast  dried  in  an  air  current  at  about   ioo°C. 
4For  other  normal  growth  curves  of  albino  rate  see  "The  Rat,"  by  Henry  H.  Donald- 
son, Wistar  Institute,  Philadelphia,  Pa. 


PHYSIOLOGICAL   CHEMISTRY 


The  curve  shown  in  Fig.  171,  below,  is  the  growth  curve  of  a  white  rat  fed  as 
just  described.1 

The  rat  pictures  reproduced  in  Figs.  172  and  173  also  show  the  influence  of 
Water-Soluble  B  in  the  diet.  The  animals  each  weighed  about  50  grams  at  the 
beginning  of  the  experiment.  At  the  end  of  a  few  weeks,  the  rat  (No.  4)  re- 
ceiving an  inadequate  supply  of  this  vitamine  showed  no  gain  in  weight,  whereas 
the  other  animal  (No.  14),  receiving  a  more  adequate  supply  of  this  growth- 
promoting  substance  weighed  115  grams. 


G/vm 


X 


171. — GROWTH  CURVE  OF  ALBINO  RAT  SHOWING 
IMPORTANCE  or  WATER-SOLUBLE  "B". 


FIG. 
(Hawk,  Fishback  and  Bergeim:  American  Journal  of  Physiology,  48,  211,  1919.) 


An  experiment  similar  to  the  above  may  be  made  by  replacing  the  casein 
by  "meat  powder"  prepared  from  fresh  lean  beef,  ground  and  dried  in  a  current 
of  air  at  about  ioo°C.  A  typical  growth  curve  from  such  an  experiment2  is 
shown  hi  Fig.  174,  page  586. 

1Hawk,  Fishback  and  Bergeinf:  American  Journal  of  Physiology,  48,  211,  1919  See 
also  Osborne  and  Mendel:  Jour.  Biol.  Chem.,  31,  149,  1917;  32,  309,1917;  Funk  and 
Macallum:  Jour.  Biol.  Chem.,  23,  413,  1915;  27,  51,  1916. 

*  Osborne  and  Mendel:  Jour.  Biol.  Chem.,  32,  309,  1917- 


METABOLISM 


585 


(b)  Demonstration  on  Fat-Soluble  A. — In  this  experiment  two  white  rats 
may  be  used  as  subjects.  Feed  them  a  diet  similar  to  the  one  given  on  p.  583, 
and  after  normal  growth  has  been  demonstrated  (two  weeks)  replace  the  butter 


FIG.  172.— RAT  (No.  14)  FED  A  DIET  CONTAINING  SUFFICIENT  WATER-SOLUBLE  "B." 

COMPARE  FIG.  173. 
(Hawk,  Smith,  and  Bergeim:  American  Journal  of  Physiology,  56,  33,  1921.) 

by  lard,  leaving  the  diet  unchanged  in  all  other  respects.  The  diet  now  contains 
little  or  no  "Fat-Soluble  A,"  and  the  rats  will  consequently  fail  to  grow.  An 
interval  of  two  weeks  is  long  enough  to  demonstrate  this  point.  See  Figs.  175 
and  176. 


FIG.  173. — RAT    (No.   4)  FED  A  DIET  DEFICIENT  IN  WATER-SOLUBLE  '"B." 

COMPARE  FIG.  172. 
(Hawk,  Smith,  and  Bergeim:  American  Journal  of  Physiology,  56,  33,  1921.) 

(c)  Demonstration  on  "Water-Soluble  C." — Feed  two  guinea-pigs,  weighing 
about  250  to  300  grams  each,  a  diet  of  rolled  oats,  hay  which  has  been  heated 
at  105  C.  for  several  hours,  and  water.  In  addition  to  the  above  give  each 


586 


PHYSIOLOGICAL    CHEMISTRY 


animal  20  c.c.  of  pasteurized  milk  daily.  Upon  the  appearance  of  scurvy,  which 
should  occur  in  from  10  days  to  2  weeks,  add  5  c.c.  of  orange  juice  to  the  daily 
ration  of  each  guinea-pig,  and  note  results.  The  onset  of  scurvy  is  evidenced 
by  a  variety  of  symptoms  chief  of  which  are  the  following.  The  joints  become 
tender  so  that  the  animal  will  wince  and  cry  when  it  is  examined,  this  tenderness 
being  often  accompanied  by  swelling  due  to  edema  or  hemorrhage.  The  animal 
soon  becomes  lethargic  instead  of  over  excitable,  and  generally  assumes  an 
unnatural  posture  such  as  holding  up  one  tender  hind  leg,  "the  scurvy  position," 


180 
160 
140 
1ZO 
100 

JO 

% 

EXPERI 

MEAT 

MENT 

POWD 

WITH 

:R 

D/ETS 
DIET 

W/THOL 
WITH  Y 

'TYEAS1 
EA5T- 

:__ 

v\ 

A 

1 
I 
i 
i 

\ 

A 

i 

i 
i 
i 
i 

20    ^ 
*DAYS^ 

m 

f7? 

\i; 

DAYS 

FIG.  174. — GROWTH  CURVE  OF  ALBINO  RAT  SHOWING 

.  IMPORTANCE  OF  WATER-SOLUBLE  "B". 
(Osborne  and  Mendel:  Journal  Biological  Chemistry,  32,  309,  1917). 

(see  Fig.  177) or  lying  with  the  side  of  its  face  resting  on  the  floor,  "face  ache 
position."  (See  Fig.  178.)  A  couple  of  days  after  orange  juice  is  added  to 
the  diet,  the  animals  should  show  signs  of  improvement.  The  length  of  time 
elapsing  before  complete  recovery  depends  upon  the  individual  case.1 

The  Care  and  Caging  of  Albino  Rats. — The  type  of  rat  cage  illus- 
trated in  Figs.  179  and  i  So  is  a  suitable  one  for  nutrition  experiments.2 

^or  further  details  concerning  scurvy  see  Hess:  ''Scurvy  Past  and  Present," 
Lippincott,  1920. 

2  This  is  the  type  of  cage  developed  and  used  by  Dr.  Thomas  B.  Osborne  and  Dr. 
Lafayette  B.  Mendel  in  their  nutrition  investigations.  See  description  of  methods  and 
technic  by  Edna  L.  Ferry,  J.  Lab.  Clin.  Med.,  5,  735,  1920. 


METABOLISM 


FIG.  175. — RAT  FED  A  DIET  DEFICIENT  IN  FAT-SOLUBLE  A  (LEFT)  AND  RAT  FED  AN  ADE- 
QUATE DIET  (RIGHT). 
(From  McCollum  "The  Newer  Knowledge  of  Nutrition.") 


c* 


m 


clays 


20 


4O 


60 


80 


/OO 


FIG.  176. — THE  FAT-SOLUBLE  VITAMINE  AND  GROWTH.  THE  DIET  CONTAINING  LARD 
WAS  DEFICIENT  IN  FAT-SOLUBLE  A,  WHILE  COD  LIVER  OIL,  BUTTER  FAT,  AND  EGG  YOLK 
FAT  ARE  RICH  IN  THIS  SUBSTANCE. 

(Osborne  and  Mendel:  Journal  of  Biological  Chemistry,  16,  434,  1913;  17,  405,  1914.) 


588  PHYSIOLOGICAL  CHEMISTRY 

Figure  179  shows  the  individual  parts  of  cages  and  Fig.  180  the  assembled 
cage.1  Animals  should  be  kept  in  a  room  with  a  fairly  constant 
temperature  (65°  to  yo°F.)  and  not  exposed  to  direct  sunlight.  Rats 
with  young  should  be  furnished  with  strips  of  paper  for  nesting.2 
Stock  animals  are  fed  a  mixed  diet  of  ordinary  foods  or  dog  biscuit3 


FIG.  177.  —  GUINEA  PIG  WITH  SCURVY.     SHOWING  "SCURVY  POSITION. 
(Hawk,  Smith  and  Bergeim:  Unpublished  data.) 


,  cup  holders,  cups,  and  other  accessories  may  be  obtained  from  the  A.  B.  Hen- 
dryx  Company  or  the  Herpich  Company,  both  of  New  Haven,  Connecticut.  These 
cages  are  9  inches  in  diameter,  8  inches  high,  made  of  Y±  inch  mesh  galvanized  wire  netting, 
and  bound  at  the  edge  with  sheet  zinc.  The  cage  has  no  bottom  but  is  set  in  an  ordinary 
enamel-ware  pan  with  sides  2%  inches  high  and  about  gYz  inches  in  diameter  at  the  bottom. 
Sides  of  pans  should  flare  enough,  so  that  they  may  be  stocked  for  storage.  Food  con- 
tainers are  porcelain  cups  2%  inches  in  diameter  and  i%  inches  high,  such  as  attached 
to  bird  cages.  Water  holders  are  2  oz.  bar  glasses.  Five  or  six  sheets  of  paper  napkin  are 
placed  in  bottom  of  pan  to  absorb  urine  and  distilled  water.  The  paper  is  covered  with 
2  discs  of  ^  inch  mesh  wire  netting.  The  cup  holder  with  cups  is  hooked  over  the  edge 
of  the  pan  and  rests  on  the  wire  disc.  Entire  cage  can  be  lifted  to  remove  rats  or  introduce 
food.  To  clean,  cages  may  be  rinsed  with  water  and  sterilized  with  steam.  Cages  should 
be  cleaned  at  least  once  a  week.  All  parts  of  cages  should  be  interchangeable.  Bedding 
is  not  necessary  except  for  rats  with  young,  if  a  proper  temperature  is  maintained. 

2Stock  animals  are  better  kept  in  rectangular  cages  18  inches  long  12  inches  wide,  and 
9  inches  high,  front  and  sides  of  ^  inch  netting,  reinforced  with  zinc;  back  and  top  of 
sheet  zinc,  top  being  hinged  and  fastened  with  a  small  brass  catch  in  front.  The  bottom 
is  heavy  netting  of  one  inch  mesh.  The  cage  rests  in  a  galvanized  pan  18^  X  12%  X  i 
inch.  The  bottom  of  the  pan  is  covered  with  one  or  two  sheets  of  thin  blotting  paper,  held 
in  place  by  ^  inch  mesh  wire  netting.  This  netting  can  easily  be  removed  and  cleaned. 
Water  cups  like  those  used  in  parrot  cages  may  be  slipped  through  an  opening  in  the  front 
of  the  cage.  Bedding  is  not  used.  A  cage  is  ordinarily  used  for  4  rats.  See  Fig.  181. 

Just  before  or  after  a  litter  of  young  is  born,  the  mother  is  best  removed  to  a  special 
cage  9  inches  square  and  9  inches  high,  like  the  other  cages  but  have  no  (see  Fig.  182) 
bottom,  as  very  young  rats  may  be  crushed  against  the  heavy  netting.  The  separate  sheet 
of  fine  netting  mentioned  above  is  used.  Crepe  paper  strips  from  the  Dennison  Company 
may  be  used  'for  bedding.  A  special  glass  tube  may  be  used  for  water.  When  the 
young  are  three  weeks  old,  they  are  transferred  to  a  larger  cage  and  the  mother  left  with 
them  until  they  are  at  least  4  weeks  old. 

3A  suitable  biscuit  may  be  obtained  from  the  Potter  &  Wrightington  Company,  Charles 
River  Avenue,  Boston. 


METABOLISM 


589 


together  with  fresh  vegetables  such  as  carrots  once  or  twice  a  week. 
Nursing  mothers  and  young  rats  receive  also  a  paste  containing  milk 
powder  60  parts,  starch  12  parts,  and  lard  28  parts.  Experimental 
diets,  whenever  possible,  are  made  into  a  semi-solid  paste,  which 
the  rats  cannot  easily  scatter.  Dry  food  mixtures  may  be  kept  for 
some  weeks. 

Animals  are  most  conveniently  weighed  on  a  spring  balance  reading 
from  o-icoo  gm.  in  5  gm.  divisions,  weights  being  estimated  to  the 
gram.  Food  cups  with  food  are  most  readily  weighed  on  a  special 
spring  balance.1  Animals  from  50-80  gm.  in  weight  are  generally 


FIG.  178. — GUINEA  PIG  WITH  SCURVY.    SHOWING  "FACE  ACHE  POSITION." 
(Special  Report  British  Medical  Research  Committee,  No.  38,  1919.) 


used  for  feeding  experiments.  They  may  be  marked  by  clipping  the 
ears  with  a  small  shears  or  by  staining  patches  of  the  fur,  and  are 
weighed  once  a  week. 

2.  Influence  of  Protein  (Amino  Acid)  Deficiency. — At  least  four  of 
the  essential  amino  acids  which  occur  in  protein  substances  cannot 
be  synthesized  in  the  animal  body.  These  are  cystine,  lysine,  trypto- 
phane  and  tyrosine.  The  acids  mentioned  must,  therefore,  be  included 
in  our  diet  if  we  are  to  be  properly  nourished.  The  following  experi- 
ments, which  may  readily  be  made  using  white  rats  as  subjects,  will 
clearly  demonstrate  the  importance  of  two  of  these  amino  acids,  i.e., 
cystine  and  lysine. 

(a)  Demonstration  on  Cystine  Deficiency. — Place  two  young  white  rats 
(40-60  grams)  in  separate  cages  (see  Fig.fiSo).  Feed  one  rat  Diet  i  and  the 
other  rat  Diet  2  as  listed  in  the  following  table : — 

xThe  rat  balance  may  be  obtained  from  the  Chatillon  Company,  New  York,  and  the 
food  balance,  from  Charles  Forschner  and  Sons,  New  York. 


590 


PHYSIOLOGICAL   CHEMISTRY 


FIG.  179.— RAT  CAGE  FOR  NUTRITION  EXPERIMENTS,  SHOWING  INDIVIDUAL  PARTS.    As 

USED  BY   OSBORNE   AND    MENDEL. 

(Ferry:  Journal  of  Laboratory  and  Clinical  Medicine,  5,  735,  1920.) 


FIG.  1 80. — RAT  CAGE  FOR  NUTRITION  EXPERIMENTS,  ASSEMBLED.    As  USED  BY  OSBORNE 

AND  MENDEL. 
(Ferry:  Journal  of  Laboratory  and  Clinical  Medicine,  5,  735,  1920.) 


METABOLISM 


591 


FIG.  181.— RAT  CAGE  FOR  STOCK  ANIMALS.    As.  USED  BY  OSBORNE  AND  MENDEL. 
(Ferry:  Journal  of  Laboratory  and  Clinical  Medicine,  5,  735,  1920.) 


FIG.  182.— BREEDING  CAGE.    As  USED  BY  OSBORNE  AND  MENDEL. 
(Ferry:  Journal  of  Laboratory  and  Clinical  Medicine,  5,  735,  1920.) 


592 


PHYSIOLOGICAL    CHEMISTRY 
CYSTINE  DEFICIENCY  DIET 


Diet  i  Diet  2 

Per  cent       Per  cent 


Cooked  Navy  bean  meal1 

Cystine 

Salt  mixture 

Butter  fat 

Lard. . 


72.00 
o.oo 
4.00 

15.00 
9.00 


80 


40 


days 


/20 


FIG.  183. — CURVE  SHOWING  INFLUENCE  OF  A  DEFICIENCY  OF  CYSTINE  IN  THE  DIET. 
(Johns  and  Finks:  Journal  of  Biological  Chemistry,  41,  379,  1920.) 

1Navy  bean  meal  cooked  3  hours  with  distilled  water,  dried  and  ground  (John  and 
Finks:  Jour.  BioL  Chem.,  41,  375,  1920).  Cystine  may  be  prepared  as  described  in  Chap- 
ter IV. 


METABOLISM 


593 


The  animal  receiving  Diet  i  will  fail  to  grow  because  of  the  deficiency  of 
cystine.  On  the  other  hand,  the  rat  receiving  Diet  2  will  grow  normally,  because 
cystine  is  present  in  proper  amount.  The  rats  should  be  weighed  at  short 
intervals.  See  Fig.  183. 


^ 
o 

x 


(f> 


31? 


o 

\f 
tueens   /i  4r  (5 

FIG.  184. — CURVE  SHOWING  INFLUENCE  OF  A  DEFICIENCY  OF  LYSINE  IN  THE  DIET. 
(Hawk,  Smith  and  Bergeim :  Unpublished  data.) 

(b)  Demonstration  of  Lysine  Deficiency. — Make  this  demonstration  the 
same  as  (a)  above,  using  the  diets  listed  in  the  following  table : 

LYSINE  DEFICIENCY  DIET 


Diet  i 
per  cent 


Diet  2 
per  cent 


Rolled  oats1 j  60.00 

Gelatine1 1  o  .00 

Dextrin  or  starch j  30 .30 

Salt  mixture ' |  4  •  7o 

Butter  fat 5-°° 


60.00 
10.00 
20.30 

4:70 

5.00 


xOat  proteins  are  low  in  lysine.     Gelatine  is  relatively  high  in  this  amino  acid  (McCol- 
him:  "Newer  Knowledge  of  Nutrition,"  New  York,  1918,  p.  170). 

38 


594 


PHYSIOLOGICAL    CHEMISTRY 


The  rat  receiving  Diet  2  will  grow  normally  because  of  the  high  lysine  content 
of  gelatine.  The  animal  receiving  Diet  i  will  fail  to  grow  properly  because  of 
lysine  deficiency.  See  Figs  184,  185,  and  186. 

3.  Influence  of  Carbohydrate  Deficiency.— Carbohydrates  occupy 
a  very  prominent  place  in  the  diet  of  man.  That  they  are  not  essential 
dietary  constituents,  at  least  for  the  white  rat,  may  be  shown  by  the 
following  experiment.1 


FIG.   185. — RAT  RECEIVING  WHEAT  PROTEIN  AND  GELATINE.     THIS  DIET  CONTAINED 

SUFFICIENT  Lysine.     COMPARE  FIG.  186. 
(Hawk,  Bergiem  and  Smith:  Unpublished  data.) 

Demonstration  on  Carbohydrate  Deficiency. — Use  young  white  rats  as 
subjects  and  proceed  as  in  experiment  i,  p.  580,  feeding  one  rat  Diet  i  and 
another  rat  Diet  2  as  given  in  the  following  table  : 


CARBOHYDRATE  DEFICIENCY  DIET 


Diet  i 
Per  cent 

Diet  2 
Per  cent 

Casein 

C(T     QO 

20  oo 

Butter  fat  

30  .00 

I  ^  .00 

Lard 

I  ^    OO 

IO   OO 

Starch  or  dextrin  

o.oo 

^  -OO 

Yeast  dried  2  gram  per  day 

o  c 

o  < 

^sborne,  Thomas  B.,  and  Mendel,  Lafayette  B.:  Soc.  Exp.  Biol.  and  Med.,  18,  136, 
1921. 

2The  yeast  is  fed  separately  0.5  gram  to  each  rat.  It  may  be  fed  as  pills  made  from 
moistened  yeast.  The  only  carbohydrate  present  in  Diet  r  is  the  very  small  amount  in 
the  dried  yeast. 


METABOLISM 


595 


Both  rats  will  grow  normally  in  spite  of  the  practical  absence  of  carbohydrates 
in  Diet  i.  In  the  case  of  man,  the  withdrawal  of  carbohydrates  is  followed  by 
acidosis  (see  p.  609).  This  acidosis  is  absent  or  much  less  pronounced  in  the 
case  of  the  white  rat. 

4.  Influence  of  Fat  Deficiency. — That  fats  are  not  essential  dietary 
constituents  provided  we  derive  sufficient  energy  from  carbohydrates 
and  proteins  and  a  proper  supply  of  "Fat-soluble  A"  from  some 
suitable  non-fat  source  is  easy  of  demonstration.1 


FIG.   1 86. — RAT  RECEIVING  WHEAT  PROTEIN  ONLY.    THIS   DIET  WAS  DEFICIENT    IN 

Lysine.     COMPARE  FIG.  185. 

Demonstration  on  Fat  Deficiency. — Place  two  young  white  rats  (30-60  grams) 
in  individual  cages.  Feed  one  the  adequate  diet  listed  as  Diet  i  in  the  following 
table.  Feed  the  other  rat  Diet  2,  in  which  alfalfa  or  spinach  is  substituted  for 
the  butter  fat. 

FAT  DEFICIENCY  DIET 


. 

Diet  i 
Per  cent 

Diet  2 
Per  cent 

Casein  

20  o 

20  o 

Starch  

?6  o 

s(6  o 

Salt  mixture  

4  ° 

40 

Yeast  

50 

50 

Butter  fat  

x  e  o 

o  o 

Dried  alfalfa  or  spinach  

o  o 

ICQ 

Both  rats  will  grow  normally,  indicating  that  a  fat-free  diet  is  satisfactory 
for  growth,  provided  the  diet  in  question  contains  ample  "Fat-Soluble  A" 
vitamine.  Hindhede2  claims  that  fat  is  not  an  essential  dietary  constituent 
provided  sufficient  fruit  and  vegetables  are  eaten  to  supply  vitamines. 

^sborne,  Thomas  B.,  and' Mendel,  Lafayette  B.:  Jour.  Biol.  Chem.,  45,  145,  1920. 
2Hindhede:  Skand.  Arch.  Physiol.,  39,  78,  1920. 


596 


PHYSIOLOGICAL  CHEMISTRY 


5.  Influence  of  Energy  Deficiency. — The  bulk  of  the  energy  in  the 
accustomed  diet  of  man  is  furnished  by  carbohydrates  and  fats.  There- 
fore, if  we  reduce  the  dietary  content  of  these  substances  to  the  mini- 
mum and  maintain  other  dietary  factors  (vitamines,  protein,  salts, 
water,  etc.)  at  a  normal  level,  we  will  not  be  properly  nourished.  The 
body  will  attempt  to  derive  the  necessary  energy  by  the  combustion 
of  body  tissues  and  a  pronounced  and  rapid  loss  in  body  weight  accom- 
panied by  other  signs  of  abnormality  will  soon  follow. 

Demonstration  on  Energy  Deficiency. — (a)  Demonstration  on  man,  following 
the  suggestions  embraced  in  the  preceding  paragraph. 

(b)  Demonstration  on  the  White  Rat. — Place  two  young  white  rats  (100-150 
grams)  in  individual  cages.  Feed  one  the  adequate  diet  listed  as  Diet  i  below. 
Feed  the  second  animal  the  same  diet  minus  the  carbohydrate.  This  animal 
will  lose  weight  rapidly,  due  to  the  low  energy  value  of  the  diet  whereas  the  other 
rat  will  grow  normally. 

ENERGY  DEFICIENCY  DIET 


Diet  i 
Grams  per  day 

Diet  2 
Grams  per  day 

Casein   ...                                                                  " 

2  .O 

2  .O 

Starch  

6.0 

o.o 

Salt  mixture 

0.4 

0.4 

Yeast  (dry)  

o.  «» 

o.  t; 

Butter  fat 

i  .  "> 

0.8 

Alfalfa  or  spinach  (dry)              .  .        

o.o 

0.7 

6.  Influence  of  Inorganic  Matter  (Calcium)  Deficiency. — A  demon- 
stration of  the  harmful  effect  following  the  elimination  of  calcium  from 
the  diet  may  readily  be  made  if  the  diets  listed  below  be  fed  to  young 
white  rats. 

DEFICIENCY  OF  CALCIUM  DIET 


Diet  i 
Per  cent 

Diet  2 
Per  cent 

Beef  liver  (steamed  and  dried)1                                           

20  .0 

2Q..O 

Casein  

IO.O 

IO.O 

NaCl  

i  .0 

1.0 

KC1  

i  .0 

I  .O 

CaCO3                                                                           

o.o 

I  .  5 

Dextrin  or  starch 

6?  .0 

63.5 

Butter  fat                                                                

3  -° 

3  -° 

liver  contains  Water-Soluble  B  and  Fat-Soluble  A  The  diet  is  adequate  except 
for  calcium  (McCollum,  Simmons,  Parsons,  Shipley,  and  Park;  Jour.  Biol.  Chem.,  45, 
333, 


METABOLISM 


597 


Demonstration  on  Calcium  Deficiency. — Place  two  young  white  rats  (40- 
60  grams)  in  separate  cages  and  feed  the  diets  listed  above.  Make  frequent 
body  weight  determinations.  The  rat  receiving  Diet  2  will  show  normal  growth. 
The  rat  receiving  Diet  i  will  fail  to  show  normal  gains  in  weight.  This  diet  is 
deficient  in  calcium.  See  Fig.  187. 

7.  Influence  of  Water  Deficiency. — (a)  The  importance  of  water  in  nutrition 
may  be  shown  very  satisfactorily  on  guinea  pigs.  Proceed  as  follows:  Place 


<:? 


ii 


.  £* 


th 


<fc 


1^22 


---4 


r  wee/ts  2  4  62/0/2 

FIG.  187. — GROWTH  CURVE  OF  RAT  WITH  AND  WITHOUT  CALCIUM  AND  PHOSPHORUS  IN 

THE  DIET. 
(Bergeim,  Smith  and  Hawk:  Unpublished  data.) 

two  young  guinea  pigs  (150-200  grams)  in  separate  cages,  and  give  each  free 
access  to  a  diet  of  hay,  oats,  and  lemon  or  orange  juice  which  has  been  dried 
rapidly  at  a  low  temperature.  Permit  one  pig  water  ad  lib.,  and  give  the  second 
pig  no  water.  The  pig  receiving  water  will  remain  normal  and  will  exhibit  normal 
gain  in  body  weight.  The  pig  receiving  no  water  will  soon  show  pronounced 
losses  in  body  weight  and  other  signs  of  abnormality.  The  animal  will  die  in  a 
short  time  unless  water  is  added  to  the  diet.  This  experiment  demonstrates 
very  clearly  that  water  is  an  indispensable  dietary  constituent.  In  fact,  water 
is  more  important  than  food.  The  following  experiment  will  show  this : 


598  PHYSIOLOGICAL    CHEMISTRY 

(b)  Food  Starvation  vs.  Water  Starvation. — Place  two  young  guinea  pigs 
(150-200  grams)  in  separate  cages.  Give  one  a  diet  such  as  that  described  on 
page  585  (c),  but  permit  the  animal  no  water.  Give  the  second  pig  no  food,  but 
permit  free  access  to  water.  The  pig  receiving  no  water  will  quickly  become 
abnormal,  and  it  will  be  necessary  to  give  it  water  to  preserve  its  life.  The 
second  pig,  which  has  access  to  w'ater1  but  receives  no  food  to  eat,  will  live 
longer  than  the  pig  receiving  an  abundance  of  dry  food.  This  little  experiment 
impresses  the  important  fact  that  man  can  live  longer  without  food  than  without 
water. 

n.  Metabolism  Procedures  Involving  the  Manipulation  of  the  Urine 

8.  Collection  and  Preservation  of  the  Urine. — In  metabolism  tests, 
such  as  those  given  in  this  chapter  the  accurate  collection  of  the  urine 
for  the  exact  24-hour  period  is  of  the  utmost  importance.     Proceed  as 
follows:  Empty  the  bladder  at  a  given  hour,  e.g.,  8  a.m.  and  discard  the 
urine.     Prepare  a  thoroughly  clean  bottle  of  proper  size,  introduce  into 
it  sufficient  toluene  to  cover  the  bottom  of  the  bottle  and  use  this  bottle 
for  the  collection  of  all  urine  voided  from  8  a.m.  until  8  a.m.  the  next 
day.     During  the  day,  when  not  actually  in  use  for  the  introduction 
of  a  urine  fraction,  the  bottle  should  be  kept  in  a  refrigerator  or  cold 
room  in  order  that  the  sample  may  not  deteriorate  before  it  is  examined. 
Measure  the  volume  of  the  sample  and  determine  its  specific  gravity 
(see  Chapter  XXII)  and  reaction  before  proceeding  to  the  quantitative 
estimation  of  any  specific  urinary  constituents. 

9.  Complete  Analysis  of  Urine. — Ingest  an  ordinary  mixed  diet  (or  any  special 
diet)  and  collect  the  urine  accurately  for  a  24-hour  period  (see  above).     Measure 
the  volume  of  the  sample,  determine  the  specific  gravity  and  preserve  the  urine 
(see  above)  until  the  following  constituents  have  been  determined  (for  Methods 
of  Analysis,  see  Chapter  XXVH).    Total  solids,  titratable  acidity,  hydrogen  ion 
concentration,  total  nitrogen,  amino-acid  nitrogen,  ammonia,  urea,  uric  acid, 
creatinine,  total  sulphur,  ethereal  sulphates,  inorganic  sulphates,  neutral  sulphur 
(by  difference)  total  phosphates  and  sodium  chloride. 

Calculate  the  nitrogen  and  sulphur  "partitions,"  i.e.,  the  percentage  of  the 
total  nitrogen  and  sulphur  which  occur  in  the  different  forms  and  tabulate  the  data 
from  the  complete  analysis.  Compare  your  results  with  those  listed  in  the  table 
on  pages  388  and  611. 

10.  Hyperglycemia   Produced   by  Carbohydrate  Ingestion. — The 

average  glucose  content  of  normal  blood  is  somewhat  less  than  o.i  per 
cent.  This  is  increased  (hyperglycemia)  on  the  ingestion  of  carbo- 
hydrate food.  The  increase  is  noted  more  quickly  after  the  ingestion  of 
monosaccharides  than  after  the  ingestion  of  the  more  complex  carbo- 
hydrates. After  the  ingestion  of  100  grams  of  glucose  or  starch  an 
increase  in  the  sugar  of  the  blood  sometimes  occurs  in  five  minutes.2 
(See  Fig.  1 88.) 

1In  case  the  pig  does  not  drink  the  water,  the  animal  should  be  fed  the  fluid  by  a  sound. 
2  Jacobson:  Bioch.  Zeit.,  56,  471,  1913. 


METABOLISM 


599 


(a)  Influence  of  Glucose. — In  the  morning  before  breakfast,  or  three  to  five 
hours  after  breakfast,  determine  the  normal  sugar  content  of  your  blood  by  means 
of  some  accurate  micromethod.  (See  Chapter  XVI.)  Ingest  100  grams  of 
glucose  dissolved  in  250  c.c.  of  water,  and  again  determine  the  blood  sugar 
level  at  intervals  of  5,  15  and  30  minutes  and  one,  two  and  three  hours.  (Plot 
a  curve  similar  to  the  one  shown  in  Fig.  188.)  The  urine  may  also  be  examined 
for  sugar  at  intervals  of  one  hour  after  the  sugar  ingestion. 

Repeat  the  experiment  on  another  day  using  250  grams  of  glucose  and  com- 
pare the  results  with  those  obtained  after  the  ingestion  of  100  grams.  Explain 
your  findings.  If  desired  this  experiment  may  be  combined  with  the  ones  on 
"Alimentary  Glycosuria,"  and  "Carbohydrate  in  Feces,"  see  pages  600  and  624. 


0.18 


0.08 


-§- 

ILL 


\ 


•, 


Wz      Z       ZVz      3 

f,  —       -        -•'-     ~ 

flours  • 

FIG.  188.— BLOOD  SUGAR  AS.  INFLUENCED  BY  DIET. 
A  =  glucose;  B  =  starch; 
C  =  starch  and  fat;  D  =  fat. 

(b)  Influence  of  Starch. — Repeat  the  experiment  as  given  above  for  glucose 
except  that  170  grams  of  white  bread  or  100  grams  of  starch  made  into  a  paste1 
are  substituted  for  the  100  grams  of  glucose. 

The  experiment  may  be  repeated  as  described  above  using  an  increased 
amount  of  starch. 

The  various  experiments  may  be  conducted  on  patients  suffering 
from  diabetis  mellitus  if  such  are  available  and  instructive  data 
collected.  The  alimentary  hyperglycemia  will  generally  be  slower 
in  reaching  its  maximum  and  will  be  more  prolonged  than  in  the 
case  of  normal  subjects.  In  some  instances  (see  Fig.  189,  p.  600) 
after  the  diabetic  has  ingested  100  grams  of  glucose  the  blood  sugar 
does  not  reach  its  maximum  until  a  period  of  two  hours  has  elapsed.2 
The  blood  sugar  also  returns  to  its  former  level  more  slowly  than  in 
the  case  of  normal  individuals. 

1  In  making  starch  paste,  rub  up  the  dry  starch  in  a  mortar  with  cold  water  and  pour  the 
suspended^  starch  granules  into  boiling  water  and  stir. 

1  Martin  and  Mason:  American  Journal  of  Medical  Sciences^  153,  50,  1917. 


6oo 


PHYSIOLOGICAL  CHEMISTRY 


s 
< 
8 

oci 

0 
00 

0) 

8 

C5 

8 

5 

o; 
o 
<n 

04 

§ 

CVJ 

o 

CO 

•^ 

$ 

u> 

BLOOD 
SUGAR 

2 

PER  CENT 

< 

0 

A 

0.34 

00* 

(V 

-**' 

^, 

*x 

0.32 

h 

< 

/ 

^ 

0.30 

ig 

i 

N 

0.28 

*U 

2-1 

i 

\ 

0.26 

_l 

£° 

/ 

v> 

0.24 

iJ2 

r  rr 

i 

<*> 

. 

0.22 

DO 

H° 

i 
f 

^ 

0.20 

ng 
y 

V 

V 

0.18 

6 

t>- 

-- 

-0 

0.16 

0.14 

0.12 

0.10 

"  0.08 

0.06 

FIG.  189. — BLOOD  SUGAR  CURVE  OF  DIABETIC  AFTER  GLUCOSE  INGESTION. 
(Martin  and  Mason:  American  Journal  of  Medical  Sciences,  153,  50,  1917.) 

ii.  Influence  of  Physical  Exercise  upon  Blood  Sugar. — After  strenuous  physical 
exertion  by  a  normally  nourished  individual  there  is  an  increase  in  the  sugar  concen- 
tration of  the  blood.1  Similar  increases  are  not  shown  by  resting  individuals  simi- 
larly nourished  nor  by  fasting  individuals  after  strenuous  physical  exercise.  This 
point  is  illustrated  in  the  following  protocol : 

INFLUENCE  OF  PHYSICAL  EXERCISE  ON  BLOOD  SUGAR  (Normal  Man) 


Day 


Experimental  conditions 


Blood 

examined, 

hour 


Blood 

sugar, 

per  cent 


Normal. 


7  A.  M. 


0.043 


Marched  8  miles  in  2  hours;  ate  200  grams  sucrose. 

12  A.  M.  | 

0.080 

Normal. 

7  A.  M. 

0.045 

Complete  rest;  ate  200  grams  sucrose. 

12  A.  M. 

0.055 

Fasting  and  complete  rest. 

7  A.  M.    ! 

0.047 

Fasting  and  complete  rest. 


12  A.  M. 


0.045 


4 

Fasting. 

!    7  A.  M.          0.047 

Fasting  and  2-hour  march  (8 

miles). 

12  A.  M. 

0.052 

1-Moraczewski:  Bioch.  Zeit.,  71,  268,  1915. 


METABOLISM 


601 


The  increase  in  blood  sugar  under  the  influence  of  exercise  occurs  rather  sooner  in 
the  diabetic  organism.    Typical  data  follow: 

Experiment. — Ingest  a  simple  uniform  diet  (see  Experiment  41,  page  625)  for 
five  days  taking  the  first  meal  after  12  o'clock  (noon)  and  the  last  one  before  10 
P.  M.  On  the  morning  of  the  second  day  (7  A.  M.)  determine  the  sugar  in  your 
blood  (see  methods,  Chapter  XVI).  About  three  hours  later  take  a  brisk  walk 
for  8  miles  covering  the  distance  in  about  two  hours  and  consume  200  grams 
sucrose  during  the  walk.  Make  a  second  analysis  of  the  blood  sugar.  On  the  third 
day  analyze  your  blood  for  sugar  at  7  A.  M.  and  again  at  noon,  remaining  quiet  in 
the  meantime.  The  fourth  day  should  be  passed  without  physical  exertion  whereas 
on  the  second  day  between  10  A.  M.  and  12  M.  a  brisk  8-mile  walk  is  taken  but  no 
sucrose  ingested.  Sugar  analyses  should  be  made  at  7  A.  M.  and  12  M.  each  day. 

INFLUENCE  OF  EXERCISE  ON  BLOOD  SUGAR  (Diabetes  Patient) 


Day 

Blood 
examined, 
hour 

Blood 
sugar, 
per 
cent 

Experimental  conditions 

i 

8A.M. 

0.062 

Rest.     Diet  consisting  of  2500  grams  milk,  300  grams 
bread,  50  grams  fat. 

8A.M. 

O.I2O 

Eight-mile  march  (2  hours).    Diet  as  above. 

3P.M. 

0.085 

1 

8A.M. 

0.055 

Rest.     Diet  as  on  first  day. 

3 

3  P.M. 

0.050 

Rest.     Diet  as  on  first  day. 

8  A.  M. 

0.050 

Rest.     Diet  as  on  first  day. 

4 

3  P.M. 

0.055 

Rest.     Diet  as  on  first  day. 

5 

8  A.  M. 

0.084 

Eight-mile  march  (2  hours).       Diet  as  on  first  day. 

Calculate  your  results,  tabulate  them  and  compare  them  with  those  given  above. 

12.  Alimentary  Glycosuria. — Normal  urine  contains  a  trace  of  glucose  but  not 
enough  to  permit  detection  by  the  ordinary  tests  used  in  urinary  analysis,  if 
more  glucose  is  ingested  than  can  be  absorbed  and  assimilated  by  the  body  the 
excess  will  be  eliminated  in  the  urine.  The  "assimilation  limit"  for  the  glucose 
has  been  exceeded,  and  a  transient  alimentary  glycosuria  results.  To  demon- 
strate this,  glycosuria  proceed  as  follows :  Before  breakfast  or  luncheon  empty 
the  bladder  and  test  the  urine  for  sugar  by  any  reliable  test  (see  Chapter  XXIV). 
If  the  test  is  negative,  ingest  along  with  the  other  articles  of  diet,  250  grams  of 
glucose,  sucrose,  or  lactose  dissolved  in  water.  Empty  the  bladder  at  the  exid 
of  every  hour  for  a  period  of  three  hours  and  test  the  urine  for  reducing  sugar 
and  the  sugar  ingested. 

Was  there  any  glycosuria  and  if  so  how  soon  after  the  sugar  ingestion  did  it 
appear?  If  no  glycosuria  resulted  repeat  the  test  on  a  subsequent  day  using 
a  larger  quantity  of  sugar.  If  desired,  the  sugar  in  the  urine  may  be 
determined  quantitatively  by  one  of  the  methods  given  in  Chapter  XXVII. 


6O2 


PHYSIOLOGICAL  CHEMISTRY 


This  experiment  may  be  made  more  complete  by  making  determinations  of 
blood  sugar  at  short  intervals  as  described  in  Experiment  10,  page  598.  If 
desired^  data  on  glycosuria,  hyperglycemia  and  carbohydrate  in  feces  (page  624) 
may  be  collected  from  one  experiment. 

13.  Absorption  of  Carbohydrate  as  Influenced  by  Fat  Ingestion. — When  fat  is 
eaten  along  with  carbohydrate  food  the  absorption  of  the  latter  is  somewhat 
delayed.  This  has  been  shown  experimentally.1  To  demonstrate  the  point  pro- 
ceed as  follows:  Determine  the  content  of  sugar  in  the  blood  at  various  intervals 
after  the  ingestion  of  170  grams  of  white  bread  as  described  in  Experiment  ro  (b), 
page  599.  Plot  a  curve  for  these  values  similar  to  the  one  shown  in  Fig.  188,  page 
599.  On  a  later  day  repeat  the  experiment  and  ingest  170  grams  of  white  bread  and 
85  grams  of  butter.  Plot  the  curve  for  these  blood  sugar  concentrations  along  with 
blood  sugar  values  obtained  after  the  ingestion  of  white  bread  as  described  above. 
Has  the  fat  exerted  any  influence  upon  the  absorption  of  the  carbohydrate?  Re- 
peat the  above  experiment  on  a  case  of  diabetes  mellitus  if  such  is  available  and 
note  that  fat  exerts  the  same  influence  upon  carbohydrate  absorption  as  it  exerts  in 
the  normal  human  body. 

14.  Time  Relations  of  Protein  Metabolism. — It  is  a  well-known 
physiological  fact  that  an  interval  elapses  between  the  ingestion  of  protein 
food  and  the  appearance  in  the  urine  of  certain  products  representing  the 
complete  catabolism  of  this  food.  For  example,  if  one  ingests  an  excess 
of  protein  material  an  interval  elapses  before  the  urine  gives  evidence 
of  the  complete  excretion  of  certain  products  representative  of  the 
catabolism  of  the  protein.  Urea  is  the  chief  of  these.  The  term  "nitro- 
gen lag"  has  been  used  to  designate  the  period  elapsing  between  the 
ingestion  of  protein  and  the  excretion  in  the  urine  of  a  quantity  of 
nitrogen  equivalent  to  that  contained  in  the  protein. 

Experiment. — Ingest  a  simple  uniform  diet  whose  exact  composition  has  been 
determined  by  analysis  or  whose  approximate  composition  has  been  estimated. 

COMPOSITION  OF  COMMON  FOODS' 


Food 

Water 

Protein 
(NX62S) 

Fat 

Carbo- 
hydrates 

Ash 

Calories  per 
pound 

Beef                         Loin 
Ribs 

Per  cent 
61.3 
57.0 
67   8 

Per  cent 
19.0 
17.8 

Per  cent. 
19.1 
24.6 

Per  cent 

Per  cent 

I  .0 

0.9 
i   i 

1125 
1338 
812 

SO    2 

16  o 

33.1 

0.8 

1642 

Mutton                   Leg 
I  Shoulder 

67-4 
67.2 

19.8 
19.5 

12.4 
12.9 



i  .  i 

I  .0 

865 
90S 

70  9 

16.8 

12.  I 

1.6 

800 

Liver 

65.6 

20.2 

3-1 

2.5 

1.3 

539 

Heart 

62  6 

20    4. 

I    O 

1  125 

T 

18  o 

92 

I    O 

719 

80  6 

8  8 

9-t 

I    I 

540 

Ham 

22     "? 

21    O 

5  8 

1266 

1  Jacobson:  Bioch.  Zeit.,  56,  471,  1913. 

1  Sherman's  "Food  Products,"  Macmillan,  1914. 


METABOLISM 


603 


Food                               Water 

Protein 
(NX6.25) 

Fat 

Carbo- 
hydrates 

Ash 

Calories  per 
pound 

:  Broilers                     Per  cent 
Chicken                  Fowl                            74-8 
63.7 

Per  cent 
21.  5 
19.3 

Per  cent 
2.5 
16.3 

Per  cent 

Per  cent 
i.i                 492 
i.o              1016 

Pf,v,                        |  Halibut                       75-4 
Fish                        !  Salmon                        64.6 

18.6 

22.0 

5-2 
12.8 

.    I.O 

1.4 

550 

922 

Oatmeal  (boiled)  i     84.5 
Cereals                   \  Rice  (boiled)          !     72.5 
Shredded  Wheat          8.1 

2.8 
2.8 

10.  5 

0.5 

O.I 

1.4 

ii.  5 
24-4 
77.  9l 

0.7 

0.2 
2.1 

280 
498 
1660 

Graham                          5.4 
Crackers                 Oatmeal                        6.3 
;Soda                              5.9 

10.  0 
II.  8 
9.8 

9.4 
II.  I 
9.1 

73.81 
69.  0' 
73.1* 

•4 

.8 
.  i 

1904 
1920 
1875 

Rroarf                           ;  White                                 35-3 
-ad                       Graham                   j     35-7 

9.2 

8.9 

1.3 
1.8 

53-  11 
52.11 

.1 
•  5 

1182 
1189 

Boiled                          75-S 
Mashed                        75.  1 
Potatoes                  Chips                              2.2 
Sweet                           51.9 

1:1 
1:1 

O.I 

3-0 
39.8 
2.1 

20.91 
17-8 
46.7 
42.1 

.0 
•  5 
4-5 
0.9 

429 

493 
2598 
903 

White                          86.2 

Egg.(henl             Se  edible  por-l     49'S 
tion                             73-7 

12.3 

IS   7 

13-4 

0.2 
33-3 

1^.5 

0.6 
i.i 

I.O 

231 
1643 

672 

Milk                                                               87.0 

3-3 

4.0 

5.0 

0.7 

314 

Butter                                                         12.7 

1-3 

84.0 

1.  9' 

3450 

Peanut  butter                                                2  .  1 

29-3 

46.5 

17.1 

50 

2741 

Consomm6                  96.0 
Soups                     Ijomato                       90.0 

Celery  (cream)           88.6 

2.5 
1.8 
3-6 

2.1 

0.4 
5.6 
7.6 
5-0 

I.I 
i.S 

1.2 

I.S 

53 
179 
232 

243 

I  .1 
0.7 
2.8 

Tapioca  pudding                                       64.5 

3-3 

3-2 

28.2 

0.8 

702 

Doughnuts                                                   18.3 

6.7 

21.  0 

53.  i» 

0.9 

1942 

Ginger  snaps                                                6.3 

6.5 

8.6 

76.  o» 

2.6 

1848 

Peas  (cooked)                                            73.8 

6.7 

3-4 

I4.6 

1-5 

525 

Lettuce                                                       94  .  7              1.2 

0.3 

2.91 

0.9 

87 

Apples                                                         84.6              0.4 

0.5 

14.2' 

0.3 

285 

Oranges                                                      86.9 

0.8 

0.2 

ii.  6 

o.S 

233 

Bananas                                                      75.3 

1-3 

0.6 

22.  O1 

0.8 

447 

Figs                                                        !     79  .  i 

I.I 

18.8 

0.6 

368 

Sandwiches            jgjfcten                    4J:J     ,       ,•;• 

12.7 

5.4 

34-5 
32.1 

1.8 
1.7 

1319 
1026 

Cheese  (American)                                    30.0 

28.8 

35-9            0.3 

5.o» 

1990 

(See  table  above.)  Continue  this  diet  from  one  to  four  days.  Collect  the 
urine  in  two-hour  periods  from  7  A.  M.  to  n  P.  M.  and  in  an  eight-hour  period  be- 
tween ii  P.  M.  and  7  A.  M.  Analyze  each  specimen  for  total  nitrogen, or  urea. 
At  the  end  of  this  preliminary  period  add  to  the  uniform  diet,  at  one  meal,  a 
weighed  quantity  (150-250  grams)  of  lean  meat  specially  prepared  and  analyzed. 
Collect  the  urine  in  periods  as  before  and  determine  total  nitrogen  or  urea. 
Calculate  the  total  nitrogen  or  urea  excretion;  tabulate  the  data  and  plot  curves 

1  Percentage  of  fiber,  included  under  carbohydrate:  shredded  wheat  (1.7),  Graham 
crackers  (1.5),  oatmeal  crackers  (1.9),  soda  crackers  (0.3),  white  bread  (0.5),  Graham 
bread  (i.i),  boiled  potatoes  (0.6),  doughnuts  (0.7),  ginger  snaps   (0.7),  lettuce  (0.7), 
apples  (1.2),  bananas  (i.o). 

2  Including  salt. 

*  Including  salt  and  sugar. 


604  PHYSIOLOGICAL   CHEMISTRY 

showing  the  course  of  the  nitrogen  excretion  on  the  various  days  of  the  experi- 
ment.   How  long  was  the  "nitrogen  lag?" 

A  less  accurate  experiment  than  the  above  but  one  which  yields 
interesting  data  may  be  carried  out  as  follows: 

Ingest  a  simple  diet  whose  nitrogen  content  can  be  estimated  with  some 
degree  of  accuracy  (see  table  above).  Collect  the  urine  hi  two-hour  periods 
from  7  A.  M.  to  ii  P.  M.  and  hi  an  eight-hour  period  from  n  P.  M.  to 
7  A.  M.  and  analyze  for  total  nitrogen  or  urea.  The  next  day  ingest  the  same  diet 
plus  150-250  grams  of  lean  meat  whose  nitrogen  content  has  been  determined  by 
analysis  or  estimated.  Collect  the  urine  as  upon  the  previous  day  and  determine 
its  total  nitrogen  or  urea  content.  Plot  curves  showing  the  course  of  the  nitrogen 
or  urea  excretion  on  each  of  the  days.  How  soon  after  the  ingestion  of  the  large 
quantity  of  meat  did  you  note  an  increase  in  the  nitrogen  or  urea  excretion? 
How  many  hours  after  the  meal  was  the  maximum  quantity  of  nitrogen  or  urea 
excreted? 

15.  Influence  of  Purine-free  and  High  Purine  Diets. — The  uric  acid 
of  the  body  has  a  two-fold  origin,  i.e.,  it  may  arise  from  the  metabolism 
of  the  purine  (nuclein)  material  of  body  tissue  (glandular  organs  in 
particular)  or  it  may  arise  from  the  ingestion  of  purine  (nuclein) 
material.  That  uric  acid  which  arises  from  the  first  source  is  called 
endogenous  while  that  which  arises  from  the  second  source  is  termed 
exogenous.  Secretory  activity  may  also  act  to  increase  the  endogenous 
uric  acid  output.  The  urine  will  therefore  contain  uric  acid  even  though 
no  precursor  of  the  acid  be  ingested.  We  may  also  increase  the  uric  acid 
output  markedly  by  ingesting  a  high  purine  diet.  However,  no  matter 
how  much  purine  material  is  eaten,  only  a  small  part  of  this  purine 
material  reappears  in  the  urine  as  uric  acid.  In  gout  it  is  claimed 
there  is  an  accumulation  of  uric  acid  in  the  blood  due  to  the  fact  that 
the  kidney  has  lost  the  ability  to  maintain  the  normal  blood  uric  acid 
level.  In  this  disease  the  excretion  of  uric  acid  may  be  low  before  an 
attack  and  increase  considerably  during  an  attack.  The  excretion  of 
exogenous  uric  acid  in  gout  is  also  much  slower  than  normal. 

Experiment. — Ingest  a  purine-free  diet  containing  about  16  grams  of  nitrogen 
and  consisting  of  egg,  cheese,  milk,  starch,  fruit,  sugar  and  water  for  a  period 
of  two  days  (for  purine  content  of  foods,  see  table,  page  605).  Determine  or 
estimate  the  nitrogen  content  (see  table,  page  602)  and  during  the  next  two 
days  substitute  sweetbreads,  thymus  or  liver  for  all  the  nitrogen  of  the  diet 
maintaining  the  calorific  value  of  the  diet  the  same  as  before.  Return  to  the 
original  purine-free  diet  for  a  third  interval  of  two  days.  During  the  final  period 
of  two  days  feed  a  diet  of  sweetbreads  or  liver  containing  50  per  cent  more 
nitrogen  than  that  of  the  first  sweetbread  period.  Collect  the  urine  for  each 
of  the  eight  days  of  the  experiment  and  determine  uric  acid,  and  total  nitrogen 
or  urea.  Note  the  rise  hi  the  uric  acid  output  during  the  sweetbread  periods. 
The  uric  acid  output  on  the  purine-free  diet  is  endogenous  in  origin.  Tabulate 
your  results.  The  following  data  were  secured  by  Taylor  and  Rose1  in  a  similar 
but  much  more  carefully  controlled  test  than  that  just  outlined. 

1  Taylor  and  Rose:  Jour.  Biol.  Chem.,  14,  419,  1913. 


METABOLISM 


605 


INFLUENCE  OF  PURINE-FREE  AND  HIGH  PURINE  DIETS 

Nitrogen  ingestion  10  grams  daily 
(Daily  Output) 


Urinary  constituents  determined 
(grams) 

Purine-free 
diet 

Purine  diet 
(medium) 

Purine  diet 
(increased) 

Purine-free 
diet 

Uric  acid  N 

O   OQ 

o  14. 

O    24. 

O   O7 

Total  nitrogen  

8.0 

8.7 

9.  1 

8  8 

UreaN  (+NH8)  

7-3 

7.1 

7-1 

7.  OS 

Creatinine           

I  .  C7 

i  .40 

i.  Si 

PURINE  CONTENT  OF  FOODS1 
(Percentage  purine  base  nitrogen) 


Analyzed  by 

Food 

Analyzed  by 

Food 
Vogel1     Hall8 

Bessau 
and 
Schmid4 

Vogel8 

Hall1 

Bessau 
and 
Schmid4 

Beef                        o  050     o  052 

0.037 

Lettuce 

0.003 

Liver   o  099     o  no 

0.093 

Cucumbers        i     .... 

None. 

Mutton  i  

0.026 

Rye  bread  o  .  014 

Trace. 

Tongue  .   . 

0.055 

White  bread... 

0.008    None. 

None. 

Chicken  1  

0.029 

Milk  

0.0002    0.0002  None. 

Thvrnus                 o  308     o  4.03 

0.330 

Eggs 

None.     None. 

None. 

God  fish  o  040  <  o  023 

0.038 

Cheese  o  .  0004 



None. 

Potatoes                o  ooi     o  0007 

0.009 

Rice 

0.0004  None. 

None. 

Pancreas  o  393  1   ,  . 

Tapioca  !  

None. 

Peas                       o  016     o  016 

0.018 

Oatmeal             i 

None. 

Spinach  0.022    

0.024 

Onions     

None. 

Hominy  0.004    



Tomatoes 

None. 

None. 

1  Other  purine-free  foods  not  listed  here  are  fruits,  butter,  cream  and  starch. 

2  Vogel:  Munch,  med.  Woch.,  58,  2433,  1911. 

*  Hall:  "The  Purine  Bodies,"  Philadelphia,  1904. 

4  Bessau  and  Schmid:  Therap.  Monatsch.,  March,  1910. 


6o6 


PHYSIOLOGICAL  CHEMISTRY 


1 6.  A  Study  of  Endogenous  Uric  Acid  Output.- — The  uric  acid  in  the 
urine  is  said  to  have  two  sources,  i.e.,  from  the  purine  material  of  the 
tissues  and  from  the  purine  material  ingested.  The  former  is  endogenous 
uric  acid,  the  latter  exogenous  uric  acid.1  The  output  of  uric  acid 
on  the  purine-free  diet  in  Experiments  15  and  17  is  endogenous. 


^  30 

"5  20 

|  '0 

° 


7  8  9  10  II  12  I  2  3  4  S  G  7  8  9  (HOURS) 


FIG.  1  90.  —  INFLUENCE  OF  PROTEIN  INGESTION  ON  ENDOGENOUS  URIC  ACID  OUTPUT. 
GLUTEN  (130  GRAMS)  INGESTED  AT  i  P.M.     (Mendel  &  Stehle:  Jour.  BioL  Chem.,  22,  215, 


Mares2  claims  that  food-stuffs  act  to  increase  the  endogenous  uric 
acid  output  by  stimulating  the  digestive  glands  to  activity.  A 
similar  finding  is  reported  by  Mendel  and  Stehle.3  The  food-stuff 
having  the  most  pronounced  influence  was  protein.  Pilocarpine 
which  stimulates  the  digestive  glands  was  found  to  increase  the  endog- 
enous uric  acid  output  whereas  atr  opine  which  inhibits  secretory 
activity  was  found  to  decrease  the  output  of  endogenous  uric  acid. 


t» 


^"789  10 II  IX  I  2345"6789   (HOURS) 

FIG.  191. — THE  ENDOGENOUS  URIC  ACID  OUTPUT  DURING  FASTING.     (Mende  &•  Stehle: 
Jour.  BioL  Chem.,  22,  215,  1915.) 

The  influence  of  protein  upon  the  endogenous  uric  acid  excretion  is 
shown  by  the  chart  in  Fig.  190.  The  fasting  output  by  the  same 
individual  is  shown,  for  comparison,  in  Fig.  191. 

Experiment. — Ingest  a  purine-free  diet  consisting  of  milk,  egg,  fruit,  cheese, 
butter,  sugar  and  bread  for  one  day.  Continue  the  diet  for  breakfast  and  lunch- 
eon the  next  day  but  eat  nothing  after  12  o'clock  noon,  until  12  o'clock  noon  the 

1  Burian  and  Schur:  Zeit.  physiol.  Chem.,  43,  532,  1904-5. 

1  Mares:  Arch.  f.  d.  ges.  Physiol.,  134,  59,  1910. 

1  Mendel  and  Stehle:  Jour.  BioL  Chem.,  22,  215,  1915. 


METABOLISM  607 

following  day,  i.e.,  the  third  day  of  the  experiment.  At  that  time  ingest  125-150 
grams  of  gluten  or  some  other  purine-free  protein  preparation.  On  the  fourth 
day  of  the  experiment  eat  nothing  until  9  P.  M. 

Collect  the  urine  each  day  hi  hour  periods  from  7  A.  M.  to  9  P.  M.  and  analyze 
for  uric  acid  (see  methods  hi  Chapter  XXVII).  Chart  your  data  similarly  to 
those  shown  hi  Figs.  190  and  191,  page  606,  and  compare  them  with  the  findings 
there  recorded. 

17.  The  Rate  of  Purine  Excretion. — The  purine  material  ingested 
by  the  average  normal  person  and  which  is  not  transformed  in  the  body 
will  be  eliminated  in  about  24  hours.     In  the  case  of  persons  afflicted 
with  gout  the  purine  elimination  is  delayed.     The  establishment  of  this 
delayed  purine  elimination  is  often  of  diagnostic  assistance. 

Demonstrate  the  rate  of  purine  excretion  as  follows:  Ingest  a  purine-free 
diet  consisting  of  egg,  milk,  cheese,  starch,  sugar,  fruit  and  water  for  two  days  and 
follow  this  by  a  day  hi  which  sweetbreads,  thymus  or  liver  is  substituted  for  one 
of  the  meals  of  the  day  (see  table  page  605  for  purine  content  of  foods).  Finish 
the  experiment  by  ingesting  the  original  purine-free  diet  for  two  days.  Collect 
each  day's  urine  and  analyze  for  uric  acid.  How  soon  after  the  sweetbread 
ingestion  was  the  original  plane  of  endogenous  uric  acid  elimination  reestab- 
lished? If  one  desires  to  locate  this  time  more  definitely  the  urine  may  be 
collected  hi  short  periods  (one  to  two  hours)  and  the  uric  acid  content  of  each 
specimen  determined.  Particularly  instructive  data  may  be  collected  by  per- 
forming the  above  experiment  on  a  gout  patient  and  upon  a  normal  person  for 
comparison. 

1 8.  A  Study  of  Creatinine  Elimination. — It  has  been  established 
that  a  normal  person  ingesting  a  creatinine-free  diet  will  excrete  a  uni- 
form quantity  of  creatinine  from  day  to  day.     The  daily  excretion  of  an 
adult  man  of  average  weight  ranges  from  1-1.5  grams.     For  data  as  to 
creatinine  excretion  of  a  60  kg.  man  see  Taylor  and  Rose's  figures  in 
table  on  page  605.     The  creatinine  excretion  depends  primarily  on  the 
active  mass  of  protoplasmic  tissue,  and  therefore,  it  is  generally  true  that 
a  fat  man  will  show  a  lower  creatinine  output  than  a  lean  man  of  like 
body  weight.     For  further  discussion  of  creatinine  see  Chapter  XXIII. 

Experiment. — Ingest  an  ordinary  mixed  diet  (non-meat)  for  a  period  of  three 
days  varying  the  character  of  the  diet  daily.  Collect  the  urine  and  analyze  for 
creatinine.  (See  Chapter  XXVII  for  methods  of  analysis.) 

Did  the  creatinine  elimination  change  with  the  change  hi  diet? 

19.  Influence  of  Water. — It  has  been  demonstrated  that  increased 
water  ingestion  influences  many  of  the  functions  and  activities  of  the 
human   body.1     The  increase   in   protein   catabolism   which  accom- 
panies high-water  intake  is  shown  in  the  following  data  collected  from 

1  Hawk:  The  relationship  of  water  to  certain  life  processes  and  more  especially  to  nu- 
trition. Read  before  American  Philosophical  Society,  Philadelphia,  Feb.,  1914.  (See 
Bioch.  Bull.,  3,  420,  1914.) 


6o8 


PHYSIOLOGICAL   CHEMISTRY 


an  experiment  upon  a  normal  man.1     In  this  experiment  the  water  in- 
gestion  at  meals  was  increased  3  liters  per  day  during  the  Water  Period. 

INFLUENCE  OF  HIGH-WATER  INTAKE  UPON  URINE  VOLUME  AND 
NITROGEN  PARTITION 


Day  of 
experi- 
ment 

Urine 
volume 

Nitrogen 

Urea- 
nitrogen 

Ammonia- 
nitrogen 

Creatinine- 
nitrogen 

Creatine- 
nitrogen 

Preliminary  Period 

4 
5 
6 

c.c. 
830 
920 
880 

grams 
12.987 
12.084 
13-183 

grams 
H.338 
11.476 
11.568 

grams 
0.288 

0.305 
0.369 

grams 
0.629 
0.619 
0.651 

grams 

Water  Period 

7 
8 
9 
10 
ii 

3440 
3840 
3670 
3610 
4020 

14.161 

I3-49I 
12.981 
12.976 
13-138 

12.596 
11.583 

II.  212 

n-455 
ji.879 

0.486 
0.499 
0-553 
0.485 
0.456 

0.610 
0.616 
0.589 
0.608 
0.589 

0.063 
0.024 

O.  IO2 
0-055 
0.1^8 

The  above  data  indicate  an  increased  catabolism  of  protein  material 
as  is  shown  by  an  increased  output  of  total  nitrogen  upon  the  first  and 
second  days  (days  7  and  8)  of  the  Water  Period.  Part  of  this  increase 
may,  however,  have  been  due  to  a  "flushing"  of  the  tissues  rather  than 
to  increased  catabolism  of  protein  structures. 

Experiments — (a)  Relation  of  Water  Intake  to  Volume  and  Specific  Gravity  of 
the  Urine. — Ingest  an  ordinary  mixed  diet  for  two  days.  Collect  the  urine  in  24- 
hour  periods.  During  the  first  day  ingest  very  little  fluid  of  any  kind  either  at 
meals  or  between  meals.  On  the  second  day  ingest  as  much  water  as  you  can 
without  physical  inconvenience.  A  person  of  average  size  should  have  no  diffi- 
culty in  drinking  5-6  quarts  per  day. 

Measure  the  volume  of  each  day's  urine  and  take  the  specific  gravity.  Note 
the  pronounced  increase  in  volume  and  the  low  specific  gravity  of  the  urine 
under  the  influence  of  high-water  ingestion. 

(b)  Influence  on  Protein  Catabolism. — That  water  stimulates  protein  catab- 
olism may  easily  be  demonstrated  as  follows:  Ingest  a  uniform  diet  (milk, 
crackers,  butter,  peanut  butter  and  water)  for  a  period  of  four  days.  During  the 
first  two  days  ingest  your  customary  volume  of  water  per  day.  During  the  last 
two  days  increase  the  water  ingestion  to  5-6  liters  per  day.  Collect  urine  in  24- 
hour  periods  and  analyze  for  total  nitrogen  by  Kjeldahl  method  (see  Chapter 
XXVII  and  note  on  page  622).  Note  the  increased  excretion  of  nitrogen  under 
the  influence  of  high-water  intake.  If  time  permits  other  nitrogenous  urinary 
constituents  may  be  determined  (see  table  above). 

1  Fowler  and  Hawk:  Jour.  Expt.  Med.,  12,  388,  1910. 


METABOLISM  609 

20.  "Salt-free"  Diet. — In  order  to  be  properly  nourished  we  must 
ingest  a  certain  amount  of  inorganic  matter  daily.     If  we  fail  to  do 
this  our  metabolic  processes  become  abnormal  and  the  urine  is  one 
index  of  this  abnormality.1 

Experiment. — Ingest  an  ordinary  mixed  diet  containing  an  ample  salt  content 
for  a  period  of  two  days.  Follow  this  period  by  the  ingestion  of  a  diet  which  has 
had  its  salt  content  reduced  to  a  very  low  value.2  Sugar  and  olive  oil  or  non- 
salted  butter  may  supply  the  bulk  of  the  calorific  part  of  the  diet  and  dialyzed  egg 
white  or  casein  or  commercial  protein  preparations,  e.g.,  plasmon,  gluten  or  glidine 
may  supply  the  protein.  Ingest  such  a  diet  for  three  days.  (This  is  an  "acid- 
forming"  diet,  see  page  613.)  Collect  the  urine  and  analyze  for  sodium  chloride, 
acidity,  ammonia  and  total  nitrogen.  Compare  the  data  from  the  normal  days 
with  those  obtained  when  the  "salt-free"  diet  was  ingested.  Test  the  urine 
(Chapter  XXVII)  and  blood  (Chapter  XVI)  for  acetone.  An  acidosis-  follows 
the  ingestion  of  a  salt-free  diet  for  a  sufficient  length  of  time. 

Did  you  feel  perfectly  normal  during  the  interval  you  were  ingesting  the 
"salt-free"  diet? 

21.  Salt-rich  Diet. — On  an  ordinary  mixed  diet  a  normal  adult 
will  daily  excrete  10-15  grams  of  chloride,  expressed  as  sodium  chloride, 
in  the  urine.     On  a  salt-free  diet  this  excretion  decreases,  whereas  if 
the  diet  contains  an  excessive  quantity  of  sodium  chloride  this  excess 
will  be  promptly  excreted  in  the  urine.     Normal  feces  contain  very 
little  sodium  chloride  even  after  excessive  sodium  chloride  ingestion 
(see  Experiment  40). 

Experiment. — Ingest  an  ordinary  mixed  diet  for  two  days.  On  each  of  the 
following  two  days  take  a  similar  diet  plus  a  weighed  amount  (e.g.,  10  grams)  of 
sodium  chloride.  Collect  the  urine  for  the  four  days  hi  24-hour  samples,  pre- 
serve and  analyze  for  sodium  chloride  (for  methods  see  Chapter  XXVH).  What 
proportion  of  the  added  chloride  was  recovered? 

If  it  is  desired  to  make  the  experiment  quantitative  in  character  ingest  a  uni- 
form diet  (see  Experiment,  page  625)  each  day  instead  of  the  ordinary  mixed  diet, 
and  examine  urine  and  feces  (see  Experiment  40)  for  chloride. 

22.  Acidosis. — Acidosis  may  be  induced  in  a  normal  person  by  the 
ingestion  of  a  "salt-free"  diet  such  as  described  in  Experiment  20, 
above,  or  by  the  ingestion  of  a  carbohydrate-free  diet.     The  acidosis 
appears   somewhat   earlier  under   the  latter   conditions.     The  non- 
carbohydrate  diet  is  rather  better  suited  for  the  demonstration  of 
acidosis  because  of  its  greater  palatability.     When  carbohydrates  are 
ingested  there  is  an  oxidation  of  fatty  acids  to  carbon  dioxide  and 
water.     When  no  carbohydrates  are  ingested  a  portion  of  the  fatty 
acids  are  converted  into  acetone  bodies.     These  are  difficult  to  oxidize 
and  are  excreted  as  such.     The  ketonuria  (excretion  of  acetone  and 

1  Taylor:  University  of  California  Publications,  Pathology,  i. 

2  It  is  practically  impossible  to  secure  an  absolutely  "salt-free"  diet. 

39 


6io 


PHYSIOLOGICAL  CHEMISTRY 


diacetic  acid)  is  particularly  pronounced.  The  following  table  shows 
the  data  obtained  in  an  actual  case  of  the  withdrawal  of  carbohydrate 
food  from  the  diet  of  a  normal  man  (von  Noorden). 

ACIDOSIS  ACCOMPANYING  CARBOHYDRATE  WITHDRAWAL 


Day 

Diet 

Excretion  of  acetone  bodies  cal- 
culated as  /3-hydroxybutyric 
acid  (grams) 

i 

Protein,  fat  and  carbohydrate. 

None. 

2 

Protein  and  fat. 

0.8 

c 

3 

Protein  and  fat. 

1.9 

4 

Protein  and  fat. 

8-7 

5 

Protein  and  fat.                                                                    20.0 

6 

Protein,  fat  and  carbohydrate. 

2.2 

I 

Experiment. — Ingest  an  ordinary  mixed  diet  for  one  day.  Follow  this  by  a 
period  of  two  to  four  days  in  which  no  digestible  carbohydrate  is  eaten.  (A  diet 
of  meat,  eggs,  butter,  agar-agar  and  water  has  a  very  low  digestible  carbohydrate 
value.)  Collect  the  urine  for  each  day  of  the  experiment,  examine  it  qualitatively 
for  acetone  bodies  (see  tests  in  Chapter  XXIV).  If  present,  determine  the  total 
acetone  bodies  quantitatively  (for  methods  see  Chapter  XXVTI).  The  blood  may 
also  be  examined  (see  Chapter  XVI).  Did  the  withdrawal  of  carbohydrate  food 
cause  an  acidosis  or  ketonuria?  How  did  it  compare  with  the  acidosis  in  the 
above  table? 

23.  "Alkaline  Tide." — For  a  time  after  a  meal  the  normal  acid 
reaction  of  the  urine  may  be  changed  to  neutral  or  alkaline.     This 
has  been  explained  as  due  to  the  withdrawal  of  hydrogen  ions  to  manu- 
facture the  hydrochloric  acid  of  the  gastric  juice. 

Experiment. — Ingest  an  ordinary  mixed  diet.  Urinate  just  before  dinner  and 
note  the  reaction  of  the  urine  to  litmus.  If  acid,  determine  the  hydrogen  ion 
concentration  by  the  method  given  hi  Chapter  XXVII.  (If  alkaline,  discard  the 
urine  and  make  the  test  on  another  day.)  After  eating  a  heavy  dinner  (meats) 
collect  the  urine  at  intervals  of  a  half -hour  and  take  the  reaction  to  litmus  and 
determine  the  hydrogen  ion  concentration  as  before.  Did  your  urine  change  hi 
reaction  after  the  meal  and  if  so  how  long  a  period  elapsed  between  the  meal  and 
the  occurrence  of  the  maximum  change  in  reaction? 

24.  The  "Partition"  of  Urinary  Nitrogen  and  Sulphur  as  Influenced 

by  Diet. — It  was  first  shown  by  Folin1  that  the  percentage  of  the  total 
nitrogen  and  total  sulphur  of  the  urine  which  appeared  in  the  form  of 
any  particular  nitrogenous  constituent  or  in  any  particular  form  of 

1  Folin:  Amer.  Jour.  PhysioL,  13,  118,  1905. 


METABOLISM 


6n 


sulphur  was  regulated  directly  by  the  extent  of  the  total  nitrogen  and 
sulphur  elimination.  This  point  is  well  illustrated  in  the  following 
table  which  contains  data  regarding  the  so-called  "partition"  or 
"distribution"  of  the  urinary  nitrogen  and  sulphur. 

THE  NITROGEN  AND  SULPHUR  "PARTITIONS"  AS  INFLUENCED  BY  DIET' 


Constituent  of  the  urine 

Normal  protein  diet 

Starch-cream  diet 

Weight,  grams 

Nitrogen, 
grams 

C/2 

^o 

^ 

8*3 
M£ 
&* 

Weight,  grams 

Nitrogen, 
grams 

C/3 

•S* 

** 

8-3 

g 

Urea. 

31-6 

14.7 

87.5 

4.72 

2.2 

61.7 

Ammonia  

0.6 

0-49 

3-0 

o-Si 

0.42 

11.3  ; 

i-SS 

0.58 

3-6 

1.61 

0.60 

17.2 

Uric  acid  . 

o.S4 

•  •• 

0.18 

i.i 

0.27 

0.09 

2.5 

Undetermined.  .  .         ... 

0.85 

4-9 

0.27 

7.5 

Total  N..  

16.8 

IOO.O 

3-6   ^ 

IOO.O 

Inorganic  SOs. 

327 

90.0 

0.46 

60.5 

Ethereal  SOS  

O.IQ 



5.2 

O.IO 



13.2 

Neutral  SO3  

0.18 

4-8 

O.2O 

26.3 

Total  SO3  

3-64 

...... 

IOO.O 

0.76 

IOO.O 

It  will  be  observed  from  an  examination  of  this  table  that  a  normal 
protein  diet  which  gave  16.8  grams  of  urinary  nitrogen  yielded  87.5 
per  cent  of  this  nitrogen  as  urea,  3  per  cent  as  ammonia,  3.6  per  cent  as 
creatinine  and  i.i  per  cent  as  uric  acid;  whereas  a  "non-protein  diet" 
(starch  and  cream  containing  about  i  gram  of  nitrogen)  which  gave 
only  3.6  grams  of  urinary  nitrogen  yielded  only  61.7  per  cent  of  this 
nitrogen  as  urea  but  gave  a  greatly  increased  percentage  output  in  the 
case  of  each  of  the  other  nitrogenous  constituents  mentioned,  e.g.,  11.3 
per  cent  as  ammonia,  17.2  per  cent  as  creatinine  and  2.5  per  cent  as 
uric  acid.  The  percentage  output  of  neutral  sulphur  was  also  greatly 
increased. 

It  will  furthermore  be  observed  that  the  actual  daily  output  of 

1  Folin:  Am.  Journ.  Physiol.,  13,  118,  1905. 


6l2 


PHYSIOLOGICAL   CHEMISTRY 


certain  of  the  constituents  is  uninfluenced  by  the  amount  of  protein 
ingested.  Among  these  are  creatinine  and  neutral  sulphur.  On  the 
other  hand  the  output  of  inorganic  sulphur  and  urea  is  more  or  less 
directly  proportional  to  the  protein  ingestion.  The  observation 
of  such  facts  as  these  led  Folin  to  formulate  his  theory  of  protein 
metabolism.1 

Experiment. — During  a  period  of  two  or  three  days  ingest  an  ordinary  mixed 
diet  containing  100-125  grams  of  protein  (16-20  grams  of  nitrogen)  per  day. 
Collect  the  urine  accurately  in  24-hour  periods  (page  598)  preserve  it  and  analyze 
the  urine  of  the  second  and  third  days  for  total  nitrogen,  urea,  creatinine,  total 
sulphur,  inorganic  sulphates,  ethereal  sulphates  and  neutral  sulphur  (by  differ- 
ence). For  methods  of  analysis  see  Chapter  XXVU.  Follow  this  period  by 
one  of  three  days  in  which  a  diet  of  starch  and  cream  having  a  similar  calorific 
value  is  ingested.  Analyze  the  urine  for  the  second  and  third  days  as  indicated 
above.  Calculate  your  results  and  tabulate  as  shown  in  the  table  on  page  611. 
How  did  the  change  in  the  diet  alter  the  metabolism  of  nitrogen  and  sulphur? 

In  calculating  the  calorific  value  of  a  diet  make  use  of  the  following  values : 

i  gram  protein 4.1  large  calories 

i  gram  fat 9.3  large  calories 

i  gram  carbohydrate 4.1  large  calories. 

25.  Protein-Sparing  Action  of  Carbohydrate  and  Fat. — The  non-nitrogenous 
nutrients,  carbohydrate  and  fat,  have  the  power  to  diminish  the  extent  of  the  catabo- 
lism of  protein  in  the  normal  human  body.  In  other  words  they  are  said  to 
"spare"  protein.  This  point  is  illustrated  in  data  reported  by  von  Noorden  and 
Dieters,  which  are  tabulated  below. 

PROTEIN-SPARING  ACTION  OF  CARBOHYDRATE  AND  FAT 


Nitrogen  ingested 

Nitrogen  in  urine 

Remarks 

12.6  grams. 

10.4  grams. 

i  a.  6  grams+2oo  grams  sucrose. 

9.0  grams. 

13  per  cent  reduction  in  protein 
catabolism. 

It  will  be  observed  that  the  addition  of  200  grams  of  sucrose  to  the  diet  was 
accompanied  by  a  decrease  of  13  per  cent  in  the  amount  of  protein  catabolized. 
It  has  been  established  that  carbohydrates  are  more  efficient  "protein  sparers" 
than  are  the  fats.  For  example  Voit  found  carbohydrate  to  produce  a  9  per  cent 
decrease  in  protein  catabolism  whereas  fats  produced  only  a  7  per  cent  decrease. 

Experiment. — Ingest  a  uniform  diet  of  known  or  estimated  nitrogen  content 
for  a  period  of  four  days.  Collect  and  preserve  the  urine  accurately  (see  page  598) 
in  24-hour  samples  and  analyze  the  excretion  of  the  third  and  fourth  days  for  total 
nitrogen.  On  the  fifth  day  add  200  grams  of  sucrose  to  the  diet.  Analyze  this  urine 

1  The  author's  article  on  "General  Considerations  of  Metabolism"  in  "Modern  Medi- 
cine" (Osier  and  McCrae)  2nd  Edition,  1914,  p.  594.  See  also  Folin:  American  Journal 
Physiol.,  13,  118,  1905. 


METABOLISM 


6l3 


also  for  total  nitrogen.     Calculate  your  results  and  tabulate  the  data  as  shown  in 
table  on  page  6n. 

Did  the  sucrose  influence  the  catabolism  of  protein  in  your  body? 

26.  Hydrogen  Ion  Concentration  of  the  Urine  as  Influenced  by 
the  Ingestion  of  Acid-Forming  and  Base-Forming  Foods. — It  has  been 
demonstrated  by  Sherman  and  Gettler1  that  vegetables  and  fruits, 
on  burning,  leave  an  ash  in  which  the  basic  elements  (sodium,  potassium, 
calcium  and  magnesium)  predominate,  whereas  cereals,  meats  and  fish 
foods  leave  an  ash  in  which  the  acid-forming  elements  (chlorine,  sulphur 
and  phosphorus)  predominate.  A  list  of  acid-forming  and  base- 
forming  foods  is  given  in  the  following  table. 

EXCESS   OF   ACID-FORMING   OR   BASE-FORMING   ELEMENTS   IN   FOODS 

(Sherman  and  Gettler) 


Article  of  Food 

Excess  acid  or 
normal  solutions 

m 

base  in  terms  of 
>.    Per  100  grams 

Acid  (c.c.) 

Base  (c.c.) 

Apples.  .  . 

*  76 

Asparagus  ;  

o-  /u 

o  81 

Bananas  

s  1-6 

Beans  (dried)  

0  -Ou 
«7    £7 

Beans  (lima,  dried)  

*6'°l 

AT      6? 

Beets  

10  86 

Cabbage  * 

Cantaloup  

•O4 

Carrots  

•4/ 

10  82 

Cauliflower  

527 

Celery  

•66 

7    78 

Crackers  

7  81 

/  •  7° 

Eggs.  . 

II    IO 

Egg-white  

52A 

Egg-yolk  

26    60 

Fish  (haddock)  

16  07 

Lemons  

5    A  e 

Lettuce  

•*K> 
777 

Meat  (lean  beef)  

13   01 

•61 

Milk  (cow's)  

227 

Oatmeal  

12   O3 

Oranges  

-     AT 

Potatoes  

0  •"•«. 
7IO 

Prunes  

2  d    4.O* 

Raisins  

2*  68 

Rice  

8  10 

-Wheat  (entire)  

Q  66 

1  Sherman  and  Gettler:  Jour.  Biol.  Chem.,  u,  323,  1912. 

1  Prunes,  plums  and  cranberries  yield  an  alkaline  ash  but  serve  to  increase  the  hydrogen 
ion  concentration  of  the  urine  because  of  their  benzoic  acid  content,  this  acid  being  syn- 
thesized with  glycocoll  in  the  kidney  and  elsewhere  to  form  hippuric  acid. 


6 14  PHYSIOLOGICAL   CHEMISTRY 

The  above  data  indicate  that  potatoes,  oranges,  raisins,  apples, 
bananas  and  cantaloups  are  important  base-forming  foods.  Among 
the  most  important  acid-forming  foods  are  found  rice,  whole  wheat 
bread,  oatmeal,  meats  and  eggs.  Certain  fruits,  e.g.,  cranberries,1  prunes 
and  plums  yield  a  basic  ash  but  are  acid-forming  foods. 

This  is  due  to  the  fact  that  they  contain  benzoic  acid  which  is 
synthesized  with  glycocoll  in  the  body  to  produce  hippuric  acid  (see 
page  619).  It  is  worthy  of  note  that  some  plant  foods  are  base-formers 
and  others  are  acid-formers.  It  is  also  an  important  fact  that  acid 
fruits  yield  a  basic  ash  (see  page  613). 

The  normal  diet  should  contain  sufficient  base-forming  elements  to 
neutralize  the  acids  formed.  If  these  acids  are  hot  neutralized  by 
the  basic  elements  in  the  diet  they  will  be  neutralized  by  the  fixed 
bases  of  the  tissues  of  the  body  and  a  seriously  deranged  metabolism 
may  result.  (See  experiment  on  "salt-free  diet/7  page  609.)  Organic 
salts  of  the  alkalis  (e.g.,  sodium  bicarbonate  or  sodium  acetate)  are  often 
given  therapeutically.  They  reduce  the  H  ion  concentration  of  the 
urine:  the  same  result  so  far  as  urine  reaction  is  concerned  may  be 
secured  by  feeding  properly  selected  base-forming  foods.  The  irigestion 
of  sodium  dihydrogen  phosphate  (NaH2PO4)  will  increase  the  acidity 
of  the  urine :  a  like  result  may  be  produced  by  feeding  properly  selected 
acid-forming  foods.  Anything  which  produces  an  increase  in  the  H 
ion  concentration  of  the  urine  will  produce  an  increase  in  the  ammonia 
output. 

On  a  mixed  diet  the  H  ion  concentration  of  the  urine2  has  been 
found  to  average  about  6.o.3  In  nephritis  the  H  ion  concentration  of 
the  urine  may  be  increased  to  5.3  or  higher.  Alkalis  have  been  used 
with  apparent  success  in  the  treatment  of  nephritis.4  It  is  evident  that 
base-forming  foods  properly  selected  should  be  suitable  dietary  articles 
for  nephritics.4  For  a  detailed  discussion  of  acid-forming  and  base- 
forming  foods  see  article  by  Blatherwick.5 

Experiment. — Ingest  a  uniform  diet  consisting  of  milk,  crackers,  butter,  pea- 
nut butter,  and  water  in  desired  quantities  for  a  period  of  three  days.  Follow  this 
by  a  period  of  six  days  during  the  first  three  of  which  considerable  quantities  of 
acid-forming  foods  (see  table  page  613)  are  added  to  the  diet.  During  the  second 

1  Radin  reports  this  berry  to  contain  0.06  per  cent  benzoic  acid  (Blatherwick:  Arch. 
Int.  Med.,  14,  409,  1914). 

*  Henderson  and  Palmer:  Jour.  Biol.  Chem.,  13,  393,  1913;  14,  81,  1913. 

8  H  ion  concentration  may  be  expressed  as  gram  of  ionized  H  per  liter  of  water.  A  neu- 
tral solution  has  a  H  ion  concentration  of  i  X  io~7,  or  0.000,000,1  gram  per  liter.  It  is 
often  customary  to  express  the  H  ion  concentration  according  to  Sorensen's  logarithmic 
notation.  For  example  instead  of  expressing  the  H  ion  concentration  of  a  neutral  solution 
as  i  X  io~7  he  expresses  it  as  7.06.  An  increasing  H  ion  concentration  decreases  this  value 
and  an  increasing  OH  ion  concentration  increases  the  value. 

4  Fisher:  Nephritis,  New  York,  1912. 

1  JJlatherwick:  Arch.  Int.  Med.,  14,  409,  1914. 


METABOLISM 


615 


half  of  the  period  (days  four  to  six)  add  an  abundance  of  base-forming  foods  to  the 
diet.  Distilled  water  should  be  used  for  drinking  purposes  and  a  uniform  volume 
should  be  ingested  daily.  Collect  the  urine  in  24-hour  periods,  preserve  and 
analyze  for  H  ion  concentration,  titratable  acidity  and  ammonia  (for  methods 
see  Chapter  XXVII).  Compare  your  results  with  those  tabulated  in  the  table 
below. 

REACTION  OF  URINE  AS  INFLUENCED  BY  DIET1 


Determi- 
nation. 

Basal 

diets* 

I 

2 

3 

4 

5 

6 

Baked  pota- 
toes (750 
grams  per 
day)  +  basal 
diet  No.  I 
(6  days) 

Rice  (210 
grams  per 
day)  +  basal 
diet  No.  i 
(4  days) 

Cranberry 
sauce  (300- 
600  grams 

V*Td*y)  + 
basal  diet, 

No.  i 
(6  days) 

Bread* 
(whole 
wheat)  450 
grams  for  I 
day+basal 
diet.  No.  i 

Prunes 
(330-550 
grams  per 
day)  -f  basal 
diet.  No.  2 
(3  days) 

Cantaloup* 
(260  grams) 
per     day)  + 
basal  diet, 
No.    2 
(5  days) 

No.  i 

No.  2 

days 

days 

H  ion  con- 
centration. 

7-19 

5-57 

7.74 

7.48-6.90 
7.14 

6.30-5.70 
6.  19 

6.80 
(Previous 
day  6.90) 

5.30-4-80 
5.07 

S.30-7.38 
6.70 

Titratable 
acidity 
(c.c.N/io) 

27S 

474 

196-216 
203 

166-297 
233 

391-488 
407 

350 

(Previous 
i  day  297) 

570-540-578 
563 

466-250 
328 

Ammonia 
N  (grams) 

0.310 

0.464 

0.221-0.248 
0.238 

o.  166-0.251 

0.219-0.391      0.280 
•  •  •     (Previous 
0.305       i  day  0.25  1) 

0.602-0.729 
0.654 

0.513-0.220 
0.310 

0.198 

27.  Hydrogen  Ion  Concentration  of  the  Urine  as  Influenced  by 
Alkali  and  Acid  Ingestion. — The  ingestion  of  certain  organic  salts  of  the 
alkalis,  e.g.,  sodium  citrate  and  sodium  bicarbonate  will  cause  a  decrease 
in  the  hydrogen  ion  concentration  of  the  urine.  The  ingestion  of  acids 


INFLUENCE  OF  INGESTED  SODIUM  BICARBONATE  ON  H  ION 
CONCENTRATION  OF  URINE 


Experiment 
Number 

Sodium 
Bicarbonate, 
Grams 

Hydrogen  Ion  Concen- 
tration before  Bicarbon- 
ate Ingestion 

Time  of  Collection  of  Specimen 
of  Urine  and  H  Ion  Concen- 
tration 

11.00 

A.M. 

12.00 

noon 

I.  00 

P.M. 

2.00 

P.M. 

3.00 
P.M. 

i 

2 

3 

4 
5 
6 

4 
8 

12 

8 
8 
8 

7.40 
5-40 

5-30 
7.40 

5-85 
6.70 

8.30 
8.50 
8.70 
8.50 

7.48 
8.30 
8.70 
8.70 

7.48 
6.50 
8.70 
8.50 
8.70 
8.50 

7.40 
6.50 
8.70 
8.50 
8.70 
8.70 

5.8s 
7.40 
8.70 
8.50 
8.30 
8.50 

7.48 

8.70 

1  Tabulated  from  data  reported  by  Blather  wick  (Arch.  Int.  Med.,  14,  409,  1914) 
Experiments  all  made  on  the  same  subject  (B). 

3  Basal  diet  No.  i  contained  100  grams  Graham  crackers,  25  grams  butter,  400  c.c.  whole 
milk  ingested  at  each  of  the  three  daily  meals.  One  apple  and  one  soft  boiled  egg  added  at 
supper.  In  diet  No.  2  whole  wheat  crackers  were  substituted  for  the  Graham  crackers. 

3  This  day  was  preceded  by  NaHCOs  ingestion  for  three  days  and  by  rice  ingestion  for 
four  days. 

4  This  diet  followed  immediately  after  the  diet  of  prunes  (see  5). 


6i6 


PHYSIOLOGICAL   CHEMISTRY 


(either  organic  or  inorganic)  or  acid  salts,  e.g.,  sodium  dihydrogen  phos- 
phate will  increase  the  hydrogen  ion  concentration  of  the  urine.  The 
alkalis  are  much  more  effective  in  producing  changes  in  reaction  than 
are  the  acids.  The  influence  of  ingested  alkali  (sodium  bicarbonate)  is 
shown  in  the  foregoing  table  containing  data  submitted  by  Henderson 
and  Palmer.1 

Blatherwick2  reports  a  decrease  in  ammonia  nitrogen  output  from 
0.256  gram  to  0.072  gram,  and  an  accompanying  decreased  acidity 
under  the  influence  of  bicarbonate  ingestion  (25  grams  in  two  days). 

The  influence  of  ingested  acid  (benzoic)  is  shown  in  the  following 
data  reported  by  Blatherwick.2 

INFLUENCE  OF  BENZOIC  ACID  INGESTION3 


Day 

Titratable  acidity 
(c.c.  N/io) 

H  ion  concentration 

Ammonia  N  (grams) 

i 

392 

6.15 

0.292 

2 

410 

6.15                                    0.374 

3 

443 

6.00 

0.422 

4 

434 

6  .  oo                                    o  .  408 

5 

468 

5.70                                    0.418 

(For  further  discussion  of  dietary  alterations  of  urine  reaction  see 
preceding  experiment.) 

Experiments.— (a)  Influence  of  Alkali.— Ingest  a  uniform  diet  consisting  of 
milk,  crackers,  butter,  peanut  butter  and  distilled  water  for  a  period  of  two 
days.  During  the  next  two  days  take  the  same  diet  and  ingest  24  grams  of 
sodium  bicarbonate  between  meals  (12  in  A.  M.  and  12  in  P.  M.).  Collect  the 
urine  in  24-hour  periods  and  analyze  it  for  titratable  acidity,  H  ion  concentra- 
tion and  ammonia.  Compare  your  results  with  those  shown  in  table  on 
page  615. 

If  desired  the  bicarbonate  may  be  given  in  one  dose  of  8-12  grams  and  the 
urine  collected  in  hourly  specimens  for  the  next  five  hours  and  each  specimen 
analyzed.  Data  from  such  experiments  are  shown  in  table  on  page  615. 

(b)  Influence  of  Acid.— Proceed  as  above  except  that  i  gram  of  benzoic  acid 
(in  capsule)  is  ingested  before  each  meal  of  the  experimental  period. 

The  experiment  may  also  be  varied  by  ingesting  10  grams  of  sodium  dihydro- 
gen phosphate  early  in  the  day  and  collecting  the  urine  in  hourly  fractions  or  in 
one  24-hour  sample. 

1  Henderson  and  Palmer:  Jour.  Biol.  Chem.,  14,  81,  1913. 
*  See  p.  614. 

3  One  gram  of  benzoic  acid  in  a  capsule  before  each  meal.  Basal  diet  No.  i  described  on 
page  615  was  used. 


METABOLISM 


6iy 


From  your  experiments  what  do  you  conclude  as  to  the  relative  efficiency  of 
acid  and  alkali  in  altering  the  reaction  of  the  urine? 

28.  Influence  of  a  High  Calorie  Non-Nitrogenous  Diet. — If  an 

individual  fasts  there  is  a  combustion  of  a  certain  amount  of  protein 
tissue  each  day  of  the  fast.  The  destruction  of  such  tissue  is  rather 
low  on  the  first  day  due  to  the  fact  that  the  glycogen  stores  of  the  body 
are  being  utilized  to  furnish  the  necessary  energy.  If  an  individual 


FIG.  192. — BERTHELOT- AT  WATER  BOMB  CALORIMETER. 

instead  of  fasting,  ingests  a  diet  of  high  calorific  value  and  very  low  in 
nitrogen  the  output  of  nitrogen  in  the  urine  of  the  third  or  fourth  day 
will  be  less  than  on  the  third  or  fourth  day  in  fasting.  This  is  due  to 
the  fact  that  the  body  derives  sufficient  energy  from  the  high  calorie 
diet  and  there  is  less  destruction  of  protein  body  tissues  than  occurs  in 


6l8  PHYSIOLOGICAL  CHEMISTRY 

fasting.     For  a  discussion  of  energy  value  of  foods  see  "Determination 
of  Fuel  Value  of  Foods,"  below,  and  the  table  on  page  602. 

Experiment. — Ingest  a  high  calorie  diet  which  is  very  low  in  nitrogen  or 
actually  non-nitrogenous.  A  satisfactory  diet  may  include  sugar,  butter,  starch, 
cream,  agar-agar  and  water.  (For  energy  values  see  below  and  table,  page 
602.)  Ingest  such  a  diet  for  three  days.  Collect  the  urine  hi  24-hour  periods, 
preserve  and  analyze  it  for  total  nitrogen,  acidity  and  ammonia.  Note  the  low 
nitrogen  excretion  on  the  third  day  as  compared  with  the  nitrogen  output  of  the 
third  day  of  fasting.  If  so  desired,  you  may  (at  some  later  date)  fast  for  three 
days  and  repeat  the  above  analyses  for  comparison. 

Determination  of  Fuel  Value  of  Food. — When  organic  substances  are  oxidized 
or  burned  in  the  human  body  they  liberate  a  certain  amount  of  heat.  This  calorific 
energy  or  heat  value  varies  according  to  the  type  of  organic  matter  undergoing 
oxidation.  Thus  the  proteins,  fats  and  carbohydrates  of  the  diet  when  they  are 
burned  in  the  body  yield  different  quantities  of  heat  per  unit  of  substance  than  do 
organic  acids,  alcohol,  etc.  The  energy  values  of  pure  protein  fat  and  carbohydrate 
are  the  following: 

Protein  =  4 .  i  large  calories  per  gram. 

Fat  =9-3  large  calories  per  gram. 

Carbohydrate  =  4.1  large  calories  per  gram. 

In  arriving  at  the  energy  value  of  any  given  diet  it  is  customary  to  burn  weighed 
samples  of  the  various  foods  in  an  oxygen  atmosphere  in  an  apparatus  called  a 
bomb  calorimeter  (see  Fig.  192,  page  617).  By  this  means  we  may  determine  how 
much  heat  is  liberated  when  the  ingested  food  is  oxidized  in  the  body.  A  correction 
must  be  made  for  the  incompletely  oxidized  substances  of  the  urine  and  feces.  A 
large  mass  of  data  concerning  the  heat  value  of  foods  has  been  collected  and  tabu- 
lated, and  it  is  therefore  possible  to  arrive  at  an  approximate  idea  of  the  energy 
value  of  a  diet  by  calculation  (see  table,  page  602).  The  bomb  colorimeter  shown 
in  Fig.  192,  page  617,  is  one  of  the  most  satisfactory  for  actual  determination  of  the 
heat  of  combustion  of  organic  substances. 

29.  Metabolism  in  Fasting. — The  metabolism  of  a  fasting  man  is 
entirely  different  from  the  metabolism  of  a  well-nourished  person. 
The  collection  and  analysis  of  the  urine  during  a  short  fast  (three 
to  seven  days)  will  demonstrate  many  important  facts.  The  following 
table,  which  contains  data  from  fasting  tests  made  in  the  author's 
laboratory,1  illustrates  some  of  the  points  in  which  fasting  metabolism 
differs  from  normal  metabolism: 

Abstinence  from  food  for  a  few  days  can  in  no  way  operate  to  the 
disadvantage,  of  a  normal  person.  In  fact  individuals  affected  with 
certain  types  of  gastro-intestinal  disorders  are  benefited  by  fasting. 

1  The  chloride,  phosphate  and  acidity  determinations  were  collected  during  one  seven- 
day  fast  and  the  other  data  collected  during  a  different  fast  on  the  same  man.  (See 
Howe,  Mattill  and  Hawk:  Jour.  Amer.  Chem.  Soc.,  33,  568,  1911;  and  Wilson  and  Hawk- 
Jour.  Amer.  Chem.  Soc.,  36,  137,  1914.) 


METABOLISM 
METABOLISM  IN  FASTING 


6lQ 


Day 

Body 

Total 

Ammonia 

Creatine 

Acidity. 

Chloride 

of 

weight, 

N 

N 

N 

c.c.  N/io 

28 

grams, 

period 

kg. 

grams 

grams 

grams 

NaOH 

grams 

NaCl 

Preliminary  Feeding  Period 

!-4 

Av.  74.16 

10.430 

O.  112 

None 

238.6 

2.768 

9.007 

Fasting  Period 

i 

73-32 

10.072 

0.288 

0.269 

328.9 

2.616 

5-035 

2 

71.98 

15.072 

0.642 

0.073 

677.1 

2.509 

3.231 

3 

70.92 

14.463 

0.862 

0.089 

770.4 

2.851 

2  539 

4 

70.24 

13.080 

I.2OI 

0.068 

664.2 

2.490 

1-253 

5 

69.61 

11.801          1.266 

0.033 

525-0 

2.376 

1.474 

6 

69.12 

11.214         1-373 

O.O22 

-462.4           1.186 

1.132 

7 

68.70 

10.734         1.371 

0.003                438.9                0.955 

I.I37 

. 

The  fasting  treatment1  is  also  being  used  with  success  in  cases  of  diabetes 
mellitus  and  in  the  treatment  of  obesity.2 

In  order  to  determine  experimentally  how  the  fasting  metabolism  differs  from 
normal  metabolism  proceed  as  follows :  Ingest  an  ordinary  mixed  diet  and  col- 
lect your  urine  (see  page  598)  for  a  day.  Measure  the  volume  and  analyze  the 
sample  for  total  nitrogen,  ammonia,  creatine,  sodium  chloride,  total  phosphates 
and  acidity3  (for  methods  see  Chapter  XXVII).  For  the  next  few  days  (three  to 
seven  as  desired)  ingest  nothing  but  water  and  collect  the  urine  accurately  and 
analyze  for  the  constituents  enumerated  above.  Tabulate  your  results  and 
compare  them  with  those  given  hi  the  table  above. 

30.  Synthesis  of  Hippuric  Acid  in  Human  Body.— -Hippuric  Acid  is 
present  in  human  urine  in  small  amount,  about  0.7  gram  being  excreted 
per  day.  The  urine  of  herbivorous  animals  contains  much  larger  quan- 
tities. This  acid  is  formed  in  the  animal  body,  by  synthesis  from  ben- 
zoic  acid  and  glycocoll  which  takes  place  in  the  kidneys  and  elsewhere.4 

Experiment. — Ingest  2  grams  of  sodium  benzoate  or  ammonium  benzoate 
before  retiring  at  night.  Collect  the  first  fraction  of  urine  voided  the  next  morn- 
ing. The  benzoate  has  been  synthesized  with  glycocoll  to  form  hippuric  acid. 
The  urine  will  therefore  be  found  to  contain  much  more  of  this  acid  than  is  nor- 
mally present.  Isolate  the  hippuric  acid  by  one  of  the  following  methods : 

(a)  First  Method.— Render  the  urine  alkaline  with  milk  of  lime,  boil  for  a  few 
moments  and  filter  while  hot.  Concentrate  the  filtrate,  over  a  burner,  to  a  small 
volume.  Cool  the  solution,  acidify  it  strongly  with  concentrated  hydrochloric 
acid  and  stand  it  in  a  cool  place  for  24  hours.  Filter  off  the  crystals  of  hippuric  acid 

1  Allen:  Amer.  Jour.  Med.  Sci.,  150,  480,  1915. 

2  Folin  and  Denis:  Jour.  BioL  Chem.,  21,  183,  1915. 

3  A  more  accurate  experiment  may  be  carried  out  by  ingesting  a  uniform  diet  of  known 
composition  (see  page  602)  for  a  few  days  before  the  fast. 

4  Kingsbury  and  Bell:  Jour.  BioL  Chem.,  21,  297,  1915. 


620  PHYSIOLOGICAL  CHEMISTRY 

which  have  formed  and  wash  them  with  a  little  cold  water.  Remove  the  crystals 
from  the  paper,  dissolve  them  in  a  very  small  amount  of  hot  water  and  percolate 
the  hot  solution  through  thoroughly  washed  animal  charcoal,  being  careful  to  wash 
out  the  last  portion  of  the  hippuric  acid  solution  with  hot  water.  Filter,  concen- 
trate the  nitrate  to  a  small  volume  and  stand  it  aside  for  crystallization.  Examine 
the  crystals  under  the  microscope  and  compare  them  with  those  in  Fig.  130,  page 
406.  This  method  is  not  as  satisfactory  as  Roaf 's  method  (see  below) . 

(6)  Roof's  Method. — Place  the  urine  in  a  casserole  or  precipitating  jar  and  add 
an  equal  volume  of  a  saturated  solution  of  ammonium  sulphate  and  1.5  cic.  of 
concentrated  sulphuric  acid  per  100  c.c.  of  urine.  Permit  the  mixture  to  stand  for 
twenty-four  hours  and  remove  the  crystals  of  hippuric  acid  by  nitration.  Purify 
the  crystals  by  recrystallization  according  to  the  directions  given  above  under  First 
Method.  Examine  the  crystals  under  the  microscope  and  compare  them  with  those 
given  in  Fig.  130,  page  406. 

It  is  possible,  by  the  above  technic,  to  isolate  hippuric  acid  in  crystalline  form 
from  as  small  a  volume  as  25-50  c.c.  of  herbivorous  urine.  The  greater  the  amount 
of  ammonium  sulphate  added  the  more  rapid  the  crystallization  until  at  the  satura- 
tion point  the  crystals  of  hippuric  acid  sometimes  form  in  about  ten  minutes. 

in.  METABOLISM  PROCEDURES  INVOLVING  THE 
MANIPULATION  OF  THE  FECES1 

31.  "Separation"  of  Feces. — In  order  to  differentiate  the  feces 
which  correspond  to  the  food  ingested  during  any  given  interval  it  is 
customary  to  cause  the  person  under  observation  to  ingest  some  sub- 
stance, at  the  beginning  and  end  of  the  period  in  question,  which  shall 
sufficiently  differ  in  color  and  consistency  from  the  surrounding  feces  as 
to  render  such  differentiation  comparatively  easy.  Two  "markers", 
very  widely  used  in  such  tests  are  wood  charcoal  and  carmine.  In 
making  an  actual  separation  of  feces  in  a  metabolism  experiment 
proceed  as  follows:  Just  preceding  or  in  the  early  part  of  the  first  meal 
(usually  breakfast)  of  the  metabolism  test,  ingest  a  gelatine  capsule 
(No.  oo)  containing  0.2-0.3  gram  of  carmine  or  charcoal.  From  this 
time  collect  all  stools  in  Hat-bottom  porcelain  dishes  and  examine  for  the 
presence  of  the  "marker."  All  fecal  matter  containing  portions  of  the 
marker  may  be  considered  as  representing  the  diet  in  question.  This 
fecal  matter  should  be  retained  and  preserved  (see  page  621).  Just 
before  or  in  the  early  part  of  the  first  meal  (usually  breakfast)  following 
the  end  of  the  metabolism  test  a  second  "marker"  in  a  gelatine  capsule 
should  be  ingested.  The  feces  should  be  carefully  inspected  until  the 
marker  makes  its  appearance.  Retain  all  fecal  matter  uncolored  by 
the  marker,  reject  the  remainder.  Frequent  difficulties  are  encountered 
in  the  practical  separation  of  feces,  but  the  character  of  such  difficulties 
will  be  most  satisfactorily  impressed  by  the  performance  of  actual 
separations. 

1  For  other  practical  work  on  feces  see  Chapter  XIV. 


METABOLISM  621 

32.  Collection  and  Preservation  of  Feces  and  the  Mixing  and 
Weighing  for  Analysis. — The  older  methods  in  vogue  in  metabolism 
work  embraced  the  analysis  of  dried  feces.     Various  investigators  later 
demonstrated  that  the  drying  of  feces  was  accompanied  by  losses  and 
changes  of  some  of  the  organic  constituents  of  the  feces.1     Therefore 
the  chemical  examination  of  all  stools  wherever  possible  should  be 
made  on  the  fresh  feces.     If  a  study  is  being  made  which  extends  over 
several  days  and  it  is  desired  to  economize  time  and  effort  in  the 
chemical  examination  the  daily  fecal  output  or  an  aliquot  portion  of  each 
stool  may  be  collected  in  a  friction-top  can  or  pail  of  suitable  size  and 
preserved  by  thymol  and  refrigeration.2     This  method  has  been  found 
satisfactory  when  the  feces  are  to  be  examined  for  inorganic  constituents 
or  total  nitrogen.     For  the  determination  of  fat,  carbohydrate,  etc., 
the  fresh  stool  should  be  employed. 

In  the  preservation  of  feces  for  the  determination  of  total  nitrogen 
the  following  simple  procedure  may  be  used,'  Introduce  each  stool  into 
a  weighed  friction-top  can  or  pail  and  place  the  vessel  in  a  cold  room  or 
refrigerator.3  At  the  end  of  the  period  mix  the  feces  thoroughly  and 
analyze  weighed  portions.  In  case  individual  stools  are  analyzed,  the 
stool  should  be  collected  in  a  weighed  flat-bottom  porcelain  dish.4  After 
mixing  the  feces  very  thoroughly  the  weight  of  dish,  spatula  and  feces  is 
determined  and  .the  weight  of  the  feces  secured  by  difference.5  A  por- 
tion of  the  well-mixed  feces  is  then  introduced  into  a  large  weighing 
bottle  containing  a  glass  hoe.  Desired  amounts  of  feces  are  then 
removed  for  analysis  and  the  exact  weight  of  such  amounts  obtained  by 
difference. 

33.  Bacterial  Nitrogen  in  Feces. — About  50  per  cent  of  the  total  nitrogen  of 
the  feces  is  made  up  of  bacterial  cells  (see  Chapter  XIV  on  Feces).    To  demon- 
strate this  point  proceed  as  follows: 

(a)  Ingest  an  ordinary  mixed  diet.  Collect  a  representative  stool  from  this 
diet  and  after  mixing  it  thoroughly  separate  the  bacterial  cells  from  a  weighed  por- 
tion as  described  in  Chapter  XIV.  After  examining  some  of  the  suspension  under 
the  microscope  and  noting  the  bacterial  cells  determine  the  bacterial  nitrogen  in 

1  Zaitschek:  Pflugers  Arch.,  98,  595,  1903. 
Schimidzu:  Bioch.  Zeit.,  28,  237,  1911. 
Konig:  Landw.  Vers.  Stat.,  38,  230. 

Frear  and  Holter:  Report,  Penn.  State  College,  p.  123,  1891. 
Emmett  and  Grindley:  Jour.  Am.  Chem.  Soc.,  31,  570,  1909. 

8  Howe,  Rutherford  and  Hawk:  Jour.  Amur.  Chem.  Soc.,  32,  1683,  1910.  This  proce- 
dure is  not  satisfactory  if  fat  is  to  be  determined  (Smith,  Miller  and  Hawk:  Jour.  Biol. 
Chem.,  21,  395,  1915).  Such  feces  shows  an  hydrolysis  of  fat  to  fatty  acid  and  a  decrease 
in  total  fat. 

3  The  author  uses  a  brine  tank  at  -i2°C.  in  which  the  feces  are  quickly  frozen. 

4  The  spatula  for  mixing  the  feces  should  be  weighed  with  the  dish. 

6  In  case  it  is  desired  an  aliquot  part  of  each  stool  may  be  placed  in  a  friction-top  can 
or  pail  and  preserved  as  a  "composite  sample"  for  the  period. 


622  PHYSIOLOGICAL  CHEMISTRY 

the  entire  volume  of  suspension  by  the  Kjeldahl  method1  (see  Chapter  XXVII). 
Also  determine  the  total  nitrogen  in  weighed  portions  of  the  original  feces  by  the 
Kjeldahl  method.  What  percentage  of  the  total  nitrogen  of  the  feces  is  bacterial 
nitrogen? 

(6)  If  it  is  desired  to  determine  the  actual  amount  of  nitrogen  which  is  excreted 
daily  in  the  feces  in  the  form  of  bacterial  cells,  proceed  as  follows :  Ingest  an  ordi- 
nary mixed  diet  for  a  period  of  three  days.  Separate  the  feces  for  this  period  accord- 
ing to  directions  given  on  page  620,  using  charcoal  for  the  first  separation  and  car- 
mine for  the  second  or  vice  versa.  Preserve  the  feces  for  the  period  according 
to  directions  given  on  page  621.  Mix  the  weighed  feces  thoroughly  and  analyze 
for  bacterial  nitrogen  and  total  nitrogen  according  to  directions  given  elsewhere 
(see  Chapters  XIV  and  XXVII).  Calculate  the  actual  output  of  bacterial  nitrogen 
per  day  and  the  percentage  of  the  total  nitrogen  of  the  feces  which  was  excreted 
per  day  in  the  form  of  bacterial  nitrogen. 

34.  "Metabolic  Product"  Nitrogen  in  Feces. — A  certain  quota  of  the  fecal 
nitrogen  is  due  to  the  presence  of  residues  of  digestive  secretions,  epithelial  cells, 
bacteria,  etc.    The  nitrogen  in  these  forms  has  been  called  "metabolic  nitrogen." 
To  determine  this  form  of  nitrogen  one  method2  of  procedure  is  as  follows:  Ingest 
a  non-nitrogenous  diet  for  a  period  of  two  days.    The  diet  may  include  desired 
quantities  of  starch,  cream,  sugar,  butler,  water  and  sodium  chloride.    About  15 
grams  of  agar-agar  should  be  added  to  the  diet  to  prevent  constipation  and  to  insure 
the  evacuation  of  approximately  the  normal  quantity  of  feces.     (For  influence 
of  agar-agar  see  Experiment  35.)     To  separate  the  feces  properly  ingest  a  capsule 
of  carmine  at  the  beginning  of  the  test  and  one  of  charcoal  at  the  end  (see  page  620). 
Preserve  the  feces  as  described  on  page  621.    After  mixing  the  feces  thoroughly 
determine  the  nitrogen  in  weighed  quantities  by  the  Kjeldahl  method3  according 
to  directions  given  in  Chapter  XXVII.     Calculate  the  quantity  of  nitrogen  elimi- 
nated per  day.     Inasmuch  as  no  nitrogen  was  ingested  the  nitrogen  present  in  the 
feces  is  of  metabolic  origin,  i.e.,  it  is  made  up  principally  of  nitrogen  in  the  form  of 
cells,  digestive  secretions  and  bacteria. 

35.  Influence   of    Indigestible  Non-Nitrogenous  Material  upon 
Fecal  Output. — This  may  be  demonstrated  by  agar-agar  ingestion. 
This  indigestible  hemicellulose  has  the  property  of  absorbing  water 
readily  and  therefore  when  ingested  it  increases  the  bulk  of  the  feces 
considerably.     This  fact  is  made  use  of  in  some  forms  of  constipation 
and  in  the  determination  of  metabolic  product  nitrogen  (see  Experi- 
ment 33). 

Experiment. — Ingest  a  uniform  diet  for  four  days.  Divide  the  interval  into 
periods  of  two  days  each,4  and  "separate"  the  feces  by  charcoal  or  carmine  (see 
Experiment  31).  On  the  third  and  fourth  days  ingest  10  grams  of  agar-agar  at 
each  meal.  Collect  the  feces  for  each  two-day  period  (see  Experiment  31, 
page  620),  and  note  the  increase  hi  the  daily  excretion  under  the  influence  of 
the  agar. ingestion.  What  was  the  increase  per  gram  of  agar? 

1  More  accurate  results  will  be  secured  if  the  bacterial  nitrogen  is  determined  on  each 
individual  stool  in  the  fresh  condition. 

2  For  a  discussion  of  other  methods  of  estimating  metabolic  product  nitrogen  see  Forbes, 
Mangels,  and  Morgan:  Jour  Agr.  Res.,  Q,  405,  1917. 

1  In  the  oxidation  process  use  10  grams  of  potassium  sulphate  instead  of  the  copper 
sulphate.     The  remainder  of  the  procedure  is  the  same  as  for  urine. 
4  Longer  periods  are  desirable  where  great  accuracy  is  desired. 


METABOLISM  623 

36.  Protein  Utilization.  —  By  "protein  utilization"  is  meant  the 
percentage  of  the  ingested  protein  which  is  actually  absorbed  and 
assimilated. 

This  may  be  determined  by  the  following  procedure:  Ingest  any  diet  of 
known  nitrogen  content  for  a  period  of  three  days1  (see  table,  page  602).  Collect 
all  feces  from  the  diet  making  the  "separations"  as  directed  on  page  620,  using 
carmine  as  the  initial  "marker"  and  charcoal  as  the  final  "marker"  or  vice 
versa.  Preserve  the  feces  as  directed  on  page  621.  Mix  the  total  feces  thor- 
oughly and  determine  the  nitrogen  by  the  Kjeldahl  method  (see  Chapter  XXVII  and 
note  on  page  622).  The  approximate  nitrogen  utilization  may  be  calculated  as 
follows  : 
(Food  nitrogen  —  Feces  nitrogen)  X  100 

Food  nitrogen  =  Approximate  percentage  nitrogen  utili- 

zation. If  it  is  desired  to  ascertain  the  actual  percentage  of  the  ingested  ni- 
trogen which  has  been  utilized  by  the  body  we  must  make  a  correction  for  meta- 
bolic nitrogen.  In  doing  this  proceed  as  follows  :  Ingest  a  non-nitrogenous  diet 
as  described  on  page  622  for  a  period  of  two  days,  using  sufficient  agar-agar  to 
insure  a  daily  fecal  output  which  shall  approxunateln  weight  that  obtained  when 
the  regular  protein  diet  was  ingested.2  Separate  and  preserve  the  feces  as 
directed  on  page  620.  Mix  thoroughly  and  analyze  for  nitrogen  according  to 
the  Kjeldahl  method  (see  Chapter  XXVII  and  note  on  page  622).  Calculate  the 
actual  percentage  utilization  of  the  diet  as  follows  : 
[Food  Nitrogen  —  (Fecal  nitrogen  —  metabolic  nitrogen)]  X  100 

=  Actual    per' 


nitrogen 

centage  nitrogen  utilization.    If  urinary  nitrogen  is  determined  the  above  data 
enable  us  to  prepare  a  nitrogen  balance  (see  Experiment  41,  page  625). 

37.  Influence  of  Defective  Mastication  pn  Food  Residues  in  Feces.  —  Rapid 
eating  accompanied  by  defective  mastication  leads  to  the  appearance  of  relatively 
large  macroscopic  food  residues  in  the  feces.  Under  some  conditions,  however,  pro- 
tein utilization  (see  above)  may  be  as  satisfactory  during  food  "bolting"  as  when 
the  food  is  very  thoroughly  masticated.3  This  problem  may  be  studied  by  the 
following  method: 

(a)  Ingest  a  diet  containing  meat  and  be  certain  to  masticate  the  diet  very 
thoroughly.  Collect  a  stool,  examine  macroscopically;  mix  carefully  and  examine 
microscopically  (see  page  233). 

(6)  Ingest  a  diet  similar  to  that  employed  in  above  experiment  (a).  "Bolt" 
the  food,  i.e.,  ingest  it  practically  without  mastication.  Examine  the  feces  as 
above.  Note  the  difference  in  the  macroscopical  and  microscopical  findings  under 
(a)  and  (b). 

If  the  nitrogen  of  food  and  feces  is  determined  we  may  calculate  the  protein 
utilization  (see  Experiment  36).  By  the  additional  determination  of  urinary 
nitrogen,  we  may  prepare  a  nitrogen  balance  (see  Experiment  41,  page  625). 

1  See  note  4,  p.  622. 

2  It  is  frequently  difficult  to  so  regulate  the  agar-agar  intake  as  to  secure  the  proper  fecal 
output.     In  such  an  event  the  proper  value  for  metabolic  nitrogen  must  be  obtained  by  cal- 
culation.    For  example  if  89.1  grams  of  feces  were  excreted  per  day  on  the  protein  diet,  and 
166.5  grams  per  day  (with  a  nitrogen  value  of  0.5  gram)  when  agar  was  employed,  the 
actual  value  for  metabolic  product  nitrogen  may  be  obtained  by  the  following  proportion, 
assuming  that  the  content  of  metabolic  nitrogen  is  proportional  to  the  weight  of  feces  ex- 
creted: 89.1  :  166.5  :  :  *  :  °-5-     x  =  0.268  gram  metabolic  nitrogen  per  day. 

3  Foster  and  Hawk:  Jour.  Amer.  Chem.  Soc.,  37,  1347,  1915. 


624  PHYSIOLOGICAL  CHEMISTRY 

38.  Fat  in  Feces. — A  normal  adult  will  digest  and  absorb  at  least 
90  per  cent  of  the  fat  in  the  diet  when  the  amount  ingested  does  not 
exceed  100  grams.     If  the  diet  contains  an  excessive  amount  of  fat, 
e.g.,  300  grams  per  day,  considerable  appears  in  the  feces.     In  pancreatic 
diseases  and  such  conditions  as  are  accompanied  by  a  decrease  in  bile 
flow  the  digestion  and  assimilation  of  fat  is  lessened. 

Experiments. — (a)  Ingest  an  ordinary  mixed  diet  containing  an  average  amount 
of  fat  per  day,  e.g.,  75-100  grams.  Collect  a  stool  and  examine  it  microscopically 
as  directed  in  Chapter  XIV.  (b)  Now  ingest  a  diet  containing  an  excessive 
quantity  of  fat,  e.g.,  300  grams  per  day.  Separate  the  feces  and  subject  a 
representative  sample  of  the  feces  from  the  high  fat  diet  to  microscopical  ex- 
amination, (c)  If  it  is  desired  the  fat  may  be  extracted  from  some  of  the  stool 
by  applying  the  principle  involved  in  the  quantitative  determination  of  fat  in  the 
Saxon  method  (see  Chapter  XIV).  Evaporate  the  ether  extract  and  identify  the 
fat  in  the  residue  by  tests  given  in  Chapter  IX. 

39.  Carbohydrate  in  Feces. — Under  normal  conditions  the  great 
bulk  of  the  soluble  carbohydrate  in  the  food  is  absorbed  from  the  intes- 
tine even  when  the  ingestion  is  high.     Hence  the  content  of  soluble 
carbohydrate  in  feces  is  low.     To  demonstrate  this  proceed  as  follows: 

(a)  Ingest  for  three  days  an  ordinary  mixed  diet  to  which  100  grams  of  glucose 
or  sucrose  is  daily  added.  Separate  and  preserve  the  feces  (see  page  620)  and 
when  the  final  "marker"  appears  extract  an  aliquot  portion  of  the  total  mixed  feces1 
with  water,  decolorize  with  boneblack,  filter,  and  after  making  the  filtrate  up  to 
a  known  volume  determine  the  sugar  by  Benedict's  method  (see  page  538). 
Calculate  the  soluble  carbohydrate  content  of  the  feces  for  the  three-day  interval, 
(b)  Proceed  as  above  with  the  exception  that  at  least  250  grams  of  sugar  should 
be  added  to  the  diet  instead  of  100  as  in  (a). 

How  did  the  daily  excretion  of  soluble  carbohydrate  in  (a)  compare  with  that 
in  (b)?  Why  is  this  so?  If  a  diet  of  known  carbohydrate  content  is  fed  this 
experiment  will  give  us  accurate  data  as  to  soluble  carbohydrate  utilization  (see 
Protein  Utilization,  page  623).  If  it  is  desired  this  experiment  may  be  combined 
with  the  hyperglycemia  and  glycosuria  experiments  on  pages  598  and  60 1.  See 
also  Experiment  43,  page  626. 

40.  Inorganic  Elements  in  the  Feces. — The  salts  of  sodium  and 
potassium  being  very  soluble  are  almost  completely  absorbed  from  the 
intestine.     The  same  is  true  of  the  chlorides  including  that  of  sodium 
which  is  of  greatest  importance.     Hence  the  alkali  metals  and  chlorides 
are  excreted  mainly  in  the  urine  and  are  found  only  in  very  small 
amounts  in  the  feces  even  when  large  amounts  are  ingested.     With 
calcium,  magnesium,  iron  and  phosphate  conditions  are  different.     Not 
only  are  salts  of  calcium,  magnesium  and  iron  less  readily  absorbed  but 
they  are  excreted  to  a  large  extent  by  way  of  the  intestinal  mucosa  rather 
than  by  the  kidneys.     Ordinarily  about  90  per  cent  of  ingested  calcium  is 

*If  time  permits  it  is  more  satisfactory  to  analyze  each  individual  stool  in  fresh 
condition. 


METABOLISM 


625 


eliminated  by  way  of  the  feces  and  a  little  less  than  half  of  the  magne- 
sium. From  20-30  per  cent  of  the  phosphorus  ingested  is  usually  found 
in  the  feces. 

Experiments. — (a)  Ingest  for  a  period  of  three  days  an  ordinary  mixed  diet 
without  added  salt  and  containing  no  milk.  Separate  the  feces  for  the  period  (see 
page  620)  and  retain  a  portion  of  the  well-mixed  feces  for  analysis. 

(b)  Proceed  as  above  with  the  exception  that  there  is  added  to  the  mixed  diet 
10  grams  of  common  salt  and  a  quart  of  milk  (containing  about  1.6  grams  of  CaO, 
0.2  gram  MgO,  1.4  grams  of  chloride  expressed  as  sodium  chloride,  and  2.2 
grams  P2O5).  Mix  feces  well  and  reserve  part  for  analysis. 

Ash  10  gram  samples  of  the  feces  from  the  above  diets.  Dissolve  with  the  aid 
of  a  little  dilute  nitric  acid,  filter  and  make  up  to  100  c.c.  Determine  in  aliquot 
portions  of  this  solution:  (i)  Chlorides  by  Volhard  method.  (2)  Calcium  and 
magnesium  by  McCrudden's  method.  (3)  Phosphorus  by  uranium  titration. 
(For  details  of  analytical  methods  see  Chapter  XXVII.)  Calculate  the  percent- 
ages of  the  added  Ca,  Mg,  P,  and  Cl  which  are  recovered  from  the  feces. 

For  a  more  detailed  study  of  chloride  excretion  combine  this  experiment  and 
Experiment  21  (see  Experiment  20). 

IV.    METABOLISM    PROCEDURES    INVOLVING    THE 
MANIPULATION   OF  BOTH  URINE  AND   FECES 

41.  Preparation  of  a  Metabolic  Balance. — This  test  entails  the 
analysis  of  the  food  ingested  and  of  the  urine  and  feces  excreted,  i.e., 
a  study  of  the  income  and  outgo.  Proceed  as  follows: 

Select  a  diet  which  is  simple,  i.e.,  consists  of  few  constituents,  and  which 
lends  itself  readily  to  accurate  chemical  analysis.  A  good  type  of  diet  for  ordi- 
nary metabolism  experiments  of  this  sort  consists  of  crackers  (graham  or  soda), 

BALANCE  OF  CALCIUM,  MAGNESIUM,  PHOSPHORUS,  SULPHUR,  AND 
NITROGEN  IN  ACROMEGALY 


Calcium 
oxide 

Magnesium 
oxide 

Phosphoric 
anhydride 

Sulphur 

Nitrogen 

Grams 

Ingestion  (daily)     „•     

I  4-04 

o  486 

3.  102 

I  .  IOO 

18.84 

Excretion  (urine) 

O    I  ^O 

o  160 

I    7OI 

I   006 

17   60 

Excretion  (feces)       

I    OQ3 

o  226 

I    OO2 

o.  iac 

I  .  IO 

Excretion  (total) 

I    2^2 

o  386 

2    7O3 

I    141 

18  70 

Retention  (daily)  

O    24.2 

O    IOO 

0.480 

O.O4Q 

o.  14. 

Retention  (per  cent)  . 

16  2 

20  6 

, 
TC   a 

41 

O.7 

40 


626  PHYSIOLOGICAL  CHEMISTRY 

milk,  butter,  water  and  agar-agar  (to  prevent  constipation).  Meat  specially 
prepared  in  quantity  sufficient  for  an  entire  experiment  may  also  be  utilized. 
Ingest  uniform  quantities  of  these  dietary  constituents  each  day  for  a  period  of 
three  days.1  Make  an  accurate  collection  of  the  urine  passed  during  this  interval 
(see  page  598).  Separate  the  feces  representing  the  three-day  period  (see  page 
620),  and  analyze  foods,  urine  and  feces.  The  balances  ordinarily  prepared  are 
those  for  nitrogen,  sulphur,  phosphorus  and  calcium.  Analytical  methods  for  the 
determination  of  these  elements  may  be  found  in  Chapter  XXVII. 

The  foregoing  table  includes  balances  obtained  in  a  metabolism  test  on 
acromegaly.2 

42.  Excretion  of  Urinary  and  Fecal  Chloride  after  a  High  Chloride  Ingestion. — 
Combine  the  procedures  outlined  under  Experiments  21  and  40,  pages  609  and 
624. 

43.  A  Study  of  the  Elimination  of  Carbohydrate  in  Urine  and  Feces  after 
Excessive  Carbohydrate  Ingestion. — Combine  the  procedures  outlined  in  Experi- 
ments 12  and  39,  pages  601  and  624. 

1  See  note  4,  p.  622. 

2  Bergeim,  Stewart  and  Hawk:  Jour.  Expt.,  Med.,  20,  218,  1914. 


REAGENTS  AND   SOLUTIONS 

Alizarin.1 — A  i  per  cent  solution  of  alizarin  mono-sodium  sulphonate 
in  water. 

Almen's  Reagent.2 — Dissolve  5  grams  of  tannic  acid  in  240  c.c.  of 
50  per  cent  alcohol  and  add  10  c.c.  of  25  per  cent  acetic  acid. 

Aluminium  Hydroxide  Cream.3— To  a  i  per  cent  solution  of  ammo- 
nium alum  at  room  temperature  add  a  slight  excess  of  a  i  per  cent  solu- 
tion of  ammonium  hydroxide.  Wash  by  decantation  until  the  wash 
water  shows  only  the  faintest  trace  of  residue  on  evaporation. 

Ammoniacal  Silver  Solution.4 — Dissolve^26  grams  of  silver  nitrate 
in  about  500  c.c.  of  water,  add  enough  ammonium  hydroxide  to  redis- 
solve  the  precipitate  which  forms  upon  the  first  addition  of  the  ammo- 
nium hydroxide  and  make  the  volume  of  the  mixture  up  to  i  liter  with 
water. 

Ammonium  Thiocyanate  Solution.5— This  solution  is  made  of  such 
a  strength  that  i  c.c.  of  it  is  equal  to  i  c.c.  of  the  standard  silver  nitrate 
solution  mentioned  below.  To  prepare  the  solution  dissolve  12.9  grams 
of  ammonium  thiocyanate,  NH4SCN,  in  a  little  less  than  a  liter  of 
water.  In  a  small  flask  place  20  c.c.  of  the  standard  silver  nitrate 
solution,  5  c.c.  of  a  cold  saturated  solution  of  ferric  alum  and  4  c.c.  of 
nitric  acid'(sp.  gr.  1.2),  add  water  to  make  the  total  volume  100  c.c.,  and 
thoroughly  mix  the  contents  of  the  flask.  Now  run  in  the  ammonium 
thiocyanate.  solution  from  a  burette  until  a  permanent  red-brown  tinge  is 
produced.  This  is  the  end-reaction  and  indicates  that  the  last  trace 
of  silver  nitrate  has  been  precipitated.  Take  the  burette  reading  and 
calculate  the  amount  of  water  necessary  to  use  in  diluting  the  ammo- 
nium thiocyanate  in  order  that  10  c.c.  of  this  solution  may  be  exactly 
equal  to  10  c.c.  of  the  silver  nitrate  solution.  Make  the  dilution  and 
titrate  again  to  be  certain  that  the  solution  is  of  the  proper  strength. 

Arnold-Lipliawsky  Reagent. — This  reagent  consists  of  two  definite 
solutions  which  are  ordinarily  preserved  separately  and  mixed  just  before 
using.  The  two  solutions  are  prepared  as  follows: 

(a)  One  per  cent  aqueous  solution  of  potassium  nitrate. 

1  Indicator  in  various  procedures,  pp.  177  and  501. 

*  Ott's  precipitation  test,  p.  444.     Determination  of  lactalbumin,  p.  346. 
3  Removal  of  protein  in  various  methods,  pp.  346,  506. 
1  Purine  base  precipitant,  p.  129. 

6  Volhard-Arnold  method,  p.  572,  and  Volhard- Harvey  method,  p.  573. 

627 


628  PHYSIOLOGICAL  CHEMISTRY 

(b)  One  gram  of  />-amino-acetophenon  dissolved  in  100  c.c.  of 
distilled  water  and  enough  hydrochloric  acid  (about  2  c.c.)  added  drop 
by  drop,  to  cause  the  solution,  which  is  at  first  yellow,  to  become  entirely 
colorless.  An  excess  of  acid  must  be  avoided. 

Asbestos  for  Suction  Filters.1 — The  asbestos  is  shredded,  placed  in  a 
wide  mouth  flask  and  covered  with  10  per  cent  HC1.  Heat  on  water- 
bath  for  five  hours.  Filter  on  Buchner  funnel,  wash  free  from  acid, 
return  to  the  flask,  cover  with  5  per  cent  NaOH  and  heat  on  water-bath 
for  three  hours.  Filter,  wash  free  from  alkali,  then  with  dilute  acid 
and  finally  with  water  until  free  from  acid.  Suspend  in  a  large  volume 
of  water,  allow  to  settle  for  five  minutes.  Pour  off  the  upper  two-thirds 
and  discard.  Repeat  the  washing  of  the  desired  coarse  portion  several 
times  until  the  supernatant  liquid  remains  nearly  clear. 

Bang's  Sugar  Reagents.2 — (a)  Acid  KCl  Solution. — Consisting 
of  1360  c.c.  of  saturated  KCl  to  which  is  added  640  c.c.  of  water  and 
1.5  c.c.  25  per  cent  HC1. 

(b)  Stock  Copper  Solution. — Introduce  into  a  1000  c.c.  flask  700  c.c. 
of  boiled  and  cooled  water.     Warm  to  about  30° C.  and  add  160  grams 
of  pure  potassium  bicarbonate  in  powder  form.    When  dissolved  add 
66  grams  of  pure  KCl.     Cool  and  then  add  100  grams  potassium  carbon- 
ate.    Finally  add  100  c.c.  of  4.4  per  cent  solution  of  pure  crystalline 
copper  sulphate.    Let  stand  a  short  time,  then  make  to  mark  with 
boiled  water.    Allow  to  stand  a  day  or  so  before  using, 

(c)  N/2oo  I  Solution. — Made    fresh    each    day.     Dilute    N/io  I 
solution  20  times.     Or  make  as  follows:  Introduce  into  a  100  c.c. 
flask  2  grams  KI,  1-2  c.c.  of  2  per  cent  KIOs  solution  and  5  c.c.  of  N/io 
HC1.    Make  to  mark  with  boiled  and  cooled  distilled  water. 

(d)  Starch  Solution. — A  i  per  cent  solution  of  Kahlbaum's  soluble 
starch  in  a  saturated  KCl  solution. 

(e)  Dilute  Copper  Solution. — Dilute  300  c.c.  of  the  stock  solution 
to  1000  c.c.     Mix  with  only  gentle  shaking.    Let  stand  several  hours 
before  using. 

Barfoed's  Solution.3 — Dissolve  9  grams  of  neutral,  crystallized 
copper  acetate  in  100  c.c.  of  water  and  add  1.2  c.c.  of  50  per  cent  acetic 
acid. 

Baryta  Mixture.4 — A  mixture  consisting  of  i  volume  of  a  saturated 
solution  of  barium  nitrate  and  2  volumes  of  a  saturated  solution  of 
barium  hydroxide. 

1  See  methods  entailing  use  of  Gooch  crucibles. 
s  Determination  of  sugar,  pages  288  and  542. 
*  Barfoed's  test,  p.  29. 
4  Isolation  of  urea  from  urine,  p.  392. 


REAGENTS  AND   SOLUTIONS  629 

Basic  Lead  Acetate  Solution.1 — This  solution  possesses  the  following 
formula: 

Lead  acetate 180  grams. 

Lead  oxide  (Litharge) no  grams. 

Distilled  water  to  make 1000  grams. 

Dissolve  the  lead  acetate  in  about  700  c.c.  of  distilled  water,  with  boiling. 
Add  this  hot  solution  to  the  finely  powdered  lead  oxide  and  boil  for  one- 
half  hour  with  occasional  stirring.  Cool,  filter  and  add  sufficient  dis- 
tilled water  to  the  filtrate  to  make  the  weight  i  kg. 

Benedict's  Solution.2 — Benedict  has  modified  the  Fehling  solution 
and  has  succeeded  in  obtaining  one  which  does  not  deteriorate  upon 
long  standing.  It  has  the  following  composition: 

Copper  sulphate 17.3  grams. 

Sodium  citrate *73.o  grams. 

Sodium  carbonate 100.0  grams. 

Distilled  water  to  make  i -liter. 

With  the  aid  of  heat  dissolve  the  sodium  citrate  and  carbonate  in 
about  800  c.c.  of  water.  Pour  (through  a  folded  filter  paper  if  neces- 
sary) into  a  glass  graduate  and  make  up  to  850  c.c.  Dissolve  the 
copper  sulphate  in  about  100  c.c.  of  water.  Pour  the  carbonate- 
citrate  solution  into  a  large  beaker  or  casserole  and  add  the  copper 
sulphate  solution  slowly,  with  constant  stirring  and  make  up  to  one 
liter.  The  mixed  solution  is  ready  for  use  and  does  not  deteriorate  upon 
long  standing. 

Benedict's  Sugar  Reagent.3 

Copper  sulphate  (crystallized) 18  .o  grams. 

Sodium  carbonate  (crystallized,  one-half  the  weight  of  the 

anhydrous  salt  may  be  used) 200.0  grams. 

Sodium  or  potassium  citrate 200 .  o  grams. 

Potassium  thiocyanate 125.0  grams. 

Potassium  ferrocyanide  (5  per  cent  solution) 5.0  c.c. 

Distilled  water  to  make  a  total  volume  of 1000.0  c.c. 

With  the  aid  of  heat  dissolve  the  carbonate,  citrate  and  thiocyanate 
in  enough  water  to  make  about  800  c.c.  of  the  mixture  and  filter  if 
necessary. 

Dissolve  the  copper  sulphate  separately  in  about  100  c.c.  of  water 
and  pour  the  solution  slowly  into  the  other  liquid,  with  constant  stirring. 
Add  the  ferrocyanide  solution,  cool  and  dilute  to  exactly  i  liter.  Of  the 
various  constituents,  the  copper  salt  only  need  be  weighed  with  exact- 
ness. Twenty-five  c.c.  of  the  reagent  are  reduced  by  50  mg.  of  glucose. 

1  Indican  determination,  p.  558. 

2  Benedict's  modification  of  Fehling's  test,  pp.  26  and  435. 
8  Quantitative  determination  of  sugar,  p.  538. 


630  PHYSIOLOGICAL   CHEMISTRY 

Benedict's   Sulphur  Reagent. 

Crystallized  copper  nitrate,  sulphur-free  or  of  known  sulphur 

content 200  grams. 

Sodium  or  potassium  chlorate 50  grams. 

Distilled  water  to 1000  c.c. 

Benzidine    Solutions    for  Volumetric    Sulphur  Determinations. 

Rosenheim  and  Drummond.—Rub  4'  grams  of  benzidine  (Kahl- 
baum)  into  a  fine  paste  with  about  10  c.c.  of  water  and  transfer  to  a 
2-liter  flask  with  the  aid  of  about  500  c.c.  of  water.  Add  500  c.c.  of  con- 
centrated HC1  (sp.  gr.  1.19)  and  make  up  to  2  liters  with  distilled 
water.  150  c.c  of  this  solution,  which  keeps  indefinitely,  are  sufficient 
to  precipitate  o.i  gram  H2SO4- 

Bertrand  Sugar  Reagents.1 — (a)  Copper  Sulphate  Solution. — Forty 
grams  of  pure  crystallized  copper  sulphate  are  dissolved  in  water  to 
make  a  liter. 

(£>)  Dissolve  200  grams  of  Rochelle  salts  and  150  grams  of  NaOH  in 
water  to  make  1000  c.c. 

(c)  Acid  Ferric  Sulphate  Solution. — Dissolve  50  grams  of  ferric  sul- 
phate in  about  200  c.c.  of  water  and  pour  into  this  a  mixture  of  200  c.c. 
of  concentrated  sulphuric  acid  diluted  with  about  400  c.c.  of  water. 
Mix  and  make  to  1000  c.c. 

(d)  Potassium  Permanganate  Solution. — Dissolve  5  grams  of  potas- 
sium  permanganate  in  water  to  make  1000  c.c.    Standardization. — 
Dissolve  0.250  gram  of  ammonium  oxalate  in  50-100  c.c.  of  water,  add 
1-2  c.c.  of  concentrated  sulphuric  acid  and  titrate  with  the  permangan- 
ate to  a  rose  color.     Multiply  the  number  of  grams  of  oxalate  used  by 
0.895  to  get  the  equivalent  in  Cu  of  the  number  of  cubic  centimeters  of 
permanganate  used.     Calculate  the  Cu  value  of  i  c.c. 

Bial's  Reagent.2 

Orcinol 1.5    grams. 

Fuming  HC1 500.00  grams. 

Ferric  chloride  (10  per  cent) 20-30  drops. 

Biuret  Reagent,  Gies.3 — This  reagent  consists  of  10  per  cent  KOH 
solution  to  which  25  c.c.  of  3  per  cent  CuSO4  solution  per  liter  has  been 
added.  This  imparts  a  slight  though  distinct  blue  color  to  the  clear 
liquid. 

Biuret  Paper  (Kantor  and  Gies).3 — Immerse  filter  paper  in  Gies' 
Biuret  Reagent  (above)  then  dry  and  cut  into  strips. 

1  Determination  of  sugar,  p.  545. 
1  Test  for  pentose,  p.  37. 
3  Protein  tests,  p.  99. 


REAGENTS   AND   SOLUTIONS  631 

Black's  Reagent1 — Made  by  dissolving  5  .grams  of  ferric  chloride 
and  0.4  gram  of  ferrous  chloride  in  100  c.c.  of  water. 

Blood  Serum. — This  may  easily  be  obtained  in  quantity  by  the 
procedure  described  under  Hemagglutination  in  the  chapter  on  Blood. 

Boas'  Reagent.2 — Dissolve  5  grams  of  resorcinol  and  3  grams  of 
sucrose  in  100  c.c.  of  50  per  cent  alcohol. 

Buffer  Solution.3 — (a)  For  Blood. — Dissolve  69  gm.  of  mono- 
sodium  phosphate  and  179  gm.  of  crystallized  disodium  phosphate  in 
800  c.c.  of  warm  distilled  water  and  dilute  to  one  liter. 

(b)  For  Urine.  Dissolve  molecular  proportions,  142  gm.  Na2HP(>4 
and  120  gm.  NaH2PO4,  or  equivalent  amounts  of  the  crystalline  salts 
in  enough  water  to  make  1000  c.c. 

Carmine-Fibrin.4 — Prepared  by  running  fibrin  through  a  meat 
chopper,  washing  carefully  and  placing  in  0.5  per  cent  ammoniacal 
carmine  solution  (very  little  excess  ammonia  should  be  present)  until 
the  maximum  coloration  of  the  fibrin  (dark  red)  is  obtained.  The  fibrin 
is  then  washed  in  water  and  in  water  acidified  with  acetic  acid.  It  is 
preserved  under  glycerol. 

Chloride   Reagents    for   Blood   Analysis.5 — (a)    Standard   Silver 
Nitrate  Solution.     Dissolve  4.791  gm.  of  C.  P.  silver  nitrate  in  distilled 
water.     Transfer  this  solution  to  a  liter  volumetric  flask  and  make  up 
to  the  mark  with  distilled  water.     Mix  thoroughly  and  preserve  in  a. 
brown  bottle,     i  c.c.  =  i  nig.  Cl. 

(b)  Standard  Thiocyanate  Solution. — As  an  approximation  about 
3  gm.  of  KCNS  or  2.5  gm.  of  NH4CNS  should  be  dissolved  in  a  liter 
of  water.     By  titration  under  the  conditions  specified  under  "Pro- 
cedure" (p.  285),  and  by  proper  dilution  prepare  a  standard  such  that 
5  c.c.  are  equivalent  to  5  c.c.  of  the  silver  nitrate  solution. 

(c)  Ferric  Ammonium  Sulphate. — The  powdered  salt  is  used. 
Cochineal    Solution.6 — A  saturated   solution  of   cochineal  in  30 

per  cent  alcohol. 

Combined  Hydrochloric  Acid  (Protein  Salt). — To  prepare  so-called 
combined  hydrochloric  acid  simply  add  a  soluble  protein  such  as  Witte's 
peptone  to  free  hydrochloric  acid  of  the  desired  strength  until  it  no 
longer  responds  to  free  acid  tests  (see  chapter  on  Gastric  Digestion). 
For  example,  if  0.2  per  cent  combined  acid  is  required  the  protein  would 
be  added  to  0.2  per  cent  free  hydrochloric  acid. 

1  Test  for  free  acid,  p.  156 

2  Black's  reaction,  p.  455. 

3 Determination  of  urea  in  blood  p.  278  and  urine  p.  514. 

4  Tests  on  proteases,  p.  12. 

5  Method  of  Whitehorn,  p.  285. 

6  Determination  of  phosphates  in  urine,  p.  568. 


632  PHYSIOLOGICAL  CHEMISTRY 

Strictly  speaking  there  is  no  such  thing  as  "combined"  acid  in  this 
sense.  When  the  protein  is  added  a  protein  salt  of  the  acid  is  formed 
which  ionizes  differently  from  the  free  acid. 

Congo  Red.1 — Dissolve  0.5  gram  of  Congo  red  in  90  c.c.  of  water 
and  add  10  c.c.  of  95  per  cent  alcohol. 

Congo  Red-Fibrin. — This  may  be  prepared  by  placing  fibrin  in 
faintly  alkaline  Congo  red  solution  and  heating  to  80° C.  The  fibrin  is 
then  washed  and  preserved  under  glycerol. 

Creatinine,  Standard  Solution  for  Colorirnetric  Method.2— Dissolve 
i  gram  of  pure  creatinine  in  1000  c.c.  of  N/io  HC1.  The  solution  con- 
tains i  mg.  of  creatinine  per  cubic  centimeter.  For  blood  analysis 
transfer  6  c.c.  of  this  solution  to  a  liter  flask,  add  10  c.c.  of  normal 
HC1,  dilute  to  mark  with  water  and  mix. 

Cross  and  Bevan's  Reagent. — Combine  two  parts  of  concentrated 
hydrochloric  acid  and  one  part  of  zinc  chloride  by  weight. 

Ehrlich's  Diazo  Reagent.3— Two  separate  solutions  should  be  pre- 
pared and  mixed  in  definite  proportions  when  needed  for  use. 

(a)  Five  grams  of  sodium  nitrite  dissolved  in  i  liter  of  distilled  water. 

(b)  Five  grams  of  sulphanilic  acid  and  50  c.c.  of  hydrochloric  acid  in 
i  liter  of  distilled  water. 

Solutions  (a)  and  (b)  should  be  preserved  in  well-stoppered  vessels 
and  mixed  in  the  proportion  i :  50  when  required.  Green  asserts  that 
greater  delicacy  is  "secured  by  mixing  the  solutions  in  the  proportion 
1:100.  The  sodium  nitrite  deteriorates  upon  standing  and  becomes 
unfit  for  use  in  the  course  of  a  few  weeks. 

Esbach's  Reagent.4 — Dissolve  10  grams  of  picric  acid  and  20  grams 
of  citric  acid  in  i  liter  of  water. 

Fehling's  Solution.5 — Fehling's  solution  is  composed  of  two  definite 
solutions — a  copper  sulphate  solution  and  an  alkaline  tartrate  solution, 
which  may  be  prepared  as  follows : 

Copper  sulphate  solution  =  34.65  grams  of  copper  sulphate  dissolved 
in  water  and  made  up  to  500  c.c. 

Alkaline  tartrate  solution  =  125  grams  of  potassium  hydroxide  and 
173  grams  of  Rochelle  salt  dissolved  in  water  and  made  up  to  500  c.c. 

These  solutions  should  be  preserved  separately  in  rubber-stoppered 
bottles  and  mixed  in  equal  volumes  when  needed  for  use.  This  is  done 
to  prevent  deterioration. 

Ferric  Alurn  Solution.6 — A  cold  saturated  solution. 

1  Test  for  free  acid,  p.  156. 

2  Determination  of  creatinine,  pp.  580  and  528. 

3  Ehrlich's  diazo  reaction,  p.  469. 

4  Esbach's  method,  p.  551. 

6  Fehling's  method,  p.  541.     Fehling's  test,  pp.  25  and  433. 
6  Volhard- Arnold  method,  p.  572. 


REAGENTS   AND   SOLUTIONS  633 

Folin-McEllroy Reagent1. — Dissolve  loog.  of  sodium  pyrophosphate, 
30  g.  of  disodium  phosphate  and  50  g.  of  dry  sodium  carbonate  in  approx- 
imately i  liter  of  water  by  the  aid  of  a  little  heat.  Dissolve  separately 
13  g.  of  copper  sulphate  in  about  200  c.c.  of  water.  Pour  the  copper 
sulphate  solution  into  the  phosphate-carbonate  solution  and  shake. 

Folin-McEllroy-Peck  Reagents  for  Sugar  in  Urine.2 — (a)  Acidified 
Copper  Sulphate  Solution. — Dissolve  59  gm.  of  CuSO4  5H2O  in  water 
together  with  2  c.c.  of  concentrated  sulphuric  acid  and  make  up  to  i 
liter.  Five  c.c.  of  this  solution  correspond  to  25  mg.  of  glucose  or 
fructose,  45  mg.  of  anhydrous  maltose,  or  40.4  mg.  of  anhydrous 
lactose. 

(b)  Phosphate-carbonate-thiocyanate  Mixture. — Powder  in  a  large 
mortar  200  gm.  of  crystallized  disodium  phosphate  (HNa2PO4-i2H2O) 
and  sprinkle  over  it  about  50  gm.  of  sodium  thiocyanate  (or  60  gm. 
of  potassium  thiocyanate).  Mix  for  10  minutes  with  pestle  and  spoon, 
giving  a  uniform  semi-liquid  paste.  Add  "about  120  gm.  of  monohy- 
drated  sodium  carbonate  (or  100  to  no  gm.  of  anhydrous  carbonate) 
and  mix  with  pestle  and  spoon  until  a  rather  fluffy,  granular  powder  is 
obtained.  To  test  the  completeness  of  the  mixing  and  5  gm.  of  the 
powder  to  5  c.c.  of  the  copper  solution;  if  any  black  specks  are  formed, 
even  temporarily,  the  mixing  is  incomplete.  A  certain  amount  of 
green  color  is,  however,  practically  unavoidable  when  this  test  is 
applied.  If  no  black  coloration  is  obtained  allow  the  mixture  to  stand 
in  the  mortar  for  a  few  hours  or  over  night  (covered  with  paper)  mix 
once  more  and  transfer  to  bottles.  In  stoppered  bottles  the  mixture 
keeps  indefinitely. 

Folin-Shaffer  Reagent.3 — This  reagent  consists  of  500  grams  of  am- 
monium sulphate,  5  grams  of  uranium  acetate,  and  60  c.c.  of  10  per 
cent  acetic  acid  in  650  c.c.  of  distilled  water. 

Folin's  Sugar  Reagent. — The  reagent  is  made  up  in  two  solutions : 
A.  Five  grams  of  crystallized  copper  sulphate  are  dissolved  in  100  c.c. 
of  hot  water  and  to  the  cooled  solution  are  added  60-70  c.c.  of  pure 
glycerol. 

B.  One  hundred  and  twenty-five  grams  of  anhydrous  potassium 
carbonate  are  dissolved  in  400  c.c.  of  water. 

One  part  of  the  glycerol-copper  solution  (A)  is  mixed  with  two  parts 
of  potassium  carbonate  solution  (B).  Only  small  portions  should 
be  mixed  at  a  time  as  the  reagent  (after  mixing)  does  not  keep  but  under- 
goes gradual  reduction. 


1  Folin-McEllroy  Test,  p.  435. 

2  Folin-McEllroy-Peck  Method,  p.  540. 

3  Folin-Shaffer  method,  p.  532. 


634  PHYSIOLOGICAL  CHEMISTRY 

Folin-Wu  Blood  Sugar  Reagents.1 — (a)  Standard  Sugar  Solutions.— 
Three  standard  sugar  solutions  should  be  on  hand:  (i)  a  stock  solution, 

1  per  cent  glucose  or  invert  sugar,  preserved  with  xylene  or  toluene; 
(2)  a  solution  containing  i  mg.  of  sugar  per  10  c.c.  (5  c.c.  of  the  stock 
solution  diluted  to  500  c.c.);  (3)  a  solution  containing  2  mg.  of  sugar  per 
10  c.c.  (5  c.c.  of  the  stock  solution  diluted  to  250  c.c.).     The  invert 
sugar  solution  has  the  advantage  that  it  can  be  easily  prepared  from 
cane  sugar,  which  is  pure. 

When  good  quality  glucose  is  available,  it  is,  of  course,  the  one  to  use. 
The  diluted  solutions  should  be  preserved  with  a  little  added  toluene 
or  xylene;  it  is  probably  better  not  to  depend  on  such  diluted  solutions 
to  keep  for  more  than  a  month,  but  the  stock  solution  should  keep 
indefinitely. 

(b)  Alkaline  Copper  Solution. — Dissolve  40  gm.  of  pure  anhydrous 
sodium  carbonate  in  about  400  c.c.  of  water  and  transfer  to  a  liter 
flask.     Add  7.5  gm.  of  tartaric  acid,  and  when  the  latter  has  dissolved 
add  4.5  gm.  of  crystallized  copper  sulfate.     Mix  and  make  up  to  a 
volume  of  i  liter.     If  the  chemicals  used  are  not  pure  a  sediment  of 
cuprous  oxide  may  form  in  the  course  of  i  or  2  weeks.     If  this  should 
happen,  remove  the  clear  supernatant  reagent  with  a  siphon,  or  filter 
through  a  good  quality  filter  paper.     The  reagent  seems  to  keep 
indefinitely.     To  test  for  the  absence  of  cuprous  copper  in  the  solution, 
transfer  2  c.c.  to  a  test  tube  and  add  2  c.c.  of  the  molybdate  phosphate 
solution;  the  deep  blue  color  of  the  copper  should  almost  completely 
vanish.     In  order  to  forestall  improper  use  of  this  reagent  attention 
should  be  called  to  the  fact  that  it  contains  extremely  little  alkali, 

2  c.c.  by  titration  (using  the  fading  of  the  blue  copper  tartrate  color 
as  indicator),  requiring  only  about  1.4  c.c.  of  normal  acid. 

(c)  Molybdate-tungstate  Solution. — Transfer  to  a  liter  beaker  35  gm. 
of  molybdic  acid  and  5  gm.  of  sodium  tungstate.    Add  200  c.c.  of 
10  per  cent  sodium  hydroxide  and  200  c.c.  of  water.     Boil  vigorously 
for  20  to  40  minutes  so  as  to  remove  nearly  the  whole  of  the  ammonia 
present  in  the  molybdic  acid.     (The  molybdic  acid  which  may  be 
obtained  from  the  Primos  Company,  Primos,  Pa.,  contains  consider- 
able ammonia.)     Cool,  dilute  to  about  350  c.c.,  and  add  125  c.c.  of 
concentrated  (85  per  cent)  phosphoric  acid.     Dilute  to  500  c.c. 

Formalin  Solution  (Neutral).2 — To  50  c.c.  of  commercial  formalde- 
hyde solution.  (30-40  per  cent)  add  i  c.c.  of  phenolphthalein  solution 
and  then  standard  alkali  solution  until  the  mixture  assumes  a  faint 
red  color.  The  solution  should  be  freshly  prepared  for  each  set  of 
determinations. 

1  Folin-Wu  blood  sugar  method,  p.  283.  2  Formol  titration  procedure,  p.  521. 


REAGENTS  AND   SOLUTIONS  635 

Furfural  Solution.1— Add  i  c.c.  of  furfural  to  1000  c.c.  of  distilled 
water. 

Fusion  Mixture. — Two  parts  of  sodium  carbonate  to  one  part  of 
potassium  nitrate. 

Guaiac  Solution.2 — Dissolve  0.5  gram  of  guaiac  resin  in  30  c.c.  of 
95  per  cent  alcohol. 

Giinzberg's  Reagent.3 — Dissolve  2  grams  of  phloroglucinol  and  i 
gram  of  vanillin  in  100  c.c.  of  95  per  cent  alcohol. 

Haines*  Solution.4 — This  solution  may  be  prepared  by  dissolving 
8.314  grams  of  copper  sulphate  in  400  c.c.  of  water  adding  40  c.c.  of 
glycerol  and  500  c.c.  of  5  per  cent  potassium  hydroxide  solution. 

Hayem's  Solution. — This  solution  has  the  following  formula: 

Mercuric  chloride o.  25  gram. 

Sodium  chloride 0.5    gram. 

Sodium  sulphate 2.5    grams. 

Distilled  water ^ 100 .  o    grams. 

Hopkin's-Cole  Reagent.5 — To  i  liter  of  a  saturated  solution  of 
oxalic  acid  add  60  grams  of  sodium  amalgam  and  allow  the  mixture 
to  stand  until  the  evolution  of  gas  ceases.  Filter  and  dilute  with  2-3 
volumes  of  water. 

Hopkin's-Cole  Reagent  (Benedict's  Modification). — Ten  grams 
of  powdered  magnesium  are  placed  in  a  large  Erlenmeyer  flask  and. 
shaken  up  with  enough  distilled  water  to  liberally  cover  the  magnesium. 
Two  hundred  and  fifty  c.c.  of  a  cold,  saturated  solution  of  oxalic  acid  is 
now  added  slowly.  The  reaction  proceeds  very  rapidly  and  with  the 
liberation  of  much  heat,  so  that  the  flask  should  be  cooled  under  running 
water  during  the  addition  of  the  acid.  The  contents  of  the  flask  are 
shaken  after  the  addition  of  the  last  portion  of  the  acid  and  then  poured 
upon  a  filter,  to  remove  the  insoluble  magnesium  oxalate.  A  little 
wash  water  is  poured  through  the  filter,  the  filtrate  acidified  with 
acetic  acid  to  prevent  the  partial  precipitation  of  the  magnesium  on  long 
standing,  and  made  up  to  a  liter  with  distilled  water.  This  solution 
contains  only  the  magnesium  salt  of  glyoxylic  acid. 

Hypobromite  Solution.6 — The  ingredients  of  this  solution  should 
be  prepared  in  the  form  of  two  separate  solutions  which  may  be  united 
as  needed. 

1  Mylius's  modification  of  Pettenkofer's  test,  pp.  211  and  449;  v.  Udr&nsky's  test,  pp. 
211  and  449. 

2  Guaiac  test,  pp.  15,  265,  and  447. 

3  Test  for  free  acid,  p.  156. 

4  Haines'  test,  p.  436. 

5  Hopkins-Cole  reaction,  p.  98. 

6  Used  for  determination  of  urea. 


636  PHYSIOLOGICAL    CHEMISTRY 

(a)  Dissolve  125  grams  of  sodium  bromide  in  water,  add  125  grams 
of  bromine  and  make  the  total  volume  of  the  solution  i  liter. 

(b)  A  solution  of  sodium  hydroxide  having  a  specific  gravity  of 
1.25.     This  is  approximately  a  22.5  per  cent  solution. 

Preserve  both  solutions  in  rubber-stoppered  bottles  and  when  needed 
for  use  mix  i  volume  of  solution  (a),  i  volume  of  solution  (&),  and  3 
volumes  of  water. 

Iodine  Solutions  (N/io).1 — Weigh  out  12.685  grams  of  pureresub- 
limed  iodine  into  a  small  weighing  bottle  using  a  porcelain  spatula. 
Dissolve  1 8  grams  of  pure  KI  in  about  150  c.c.  of  water.  Transfer  the 
iodine  to  a  liter  flask  washing  out  the  last  traces  with  some  of  the  KI 
solution,  which  is  then  poured  into  the  flask.  Stopper  and  shake 
occasionally  until  dissolved.  If  necessary  a  few  more  crystals  of  KI 
may  be  added  to  aid  solution.  Dilute  to  the  mark  and  mix  well. 
Keep  in  glass-stoppered  bottle  in  cool  dark  place.  Standardize  at  once 
against  N/io  sodium  thiosulphate  solution.  Measure  out  accurately 
25  c.c.  of  the  iodine  solution  into  an  Erlenmeyer  flask,  run  in  sodium 
thiosulphate  until  the  color  is  pale  yellow,  then  add  a  few  cubic  centi- 
meters of  a  i  per  cent  solution  of  starch  (preferably  soluble  starch) 
and  titrate  to  disappearance  of  blue  color.  Care  should  be  taken  near 
the  end  point. 

Iodine  Solution.2 — Prepare  a  2  per  cent  solution  of  potassium  iodide 
and  add  sufficient  iodine  to  color  it  a  deep  yellow. 

Iodine-Zinc  Chloride  Reagent.3 — Dissolve  20  grams  of  zinc  chloride 
in  8.5  c.c.  of  water.  Cool,  and  introduce  iodine  solution  (3  grams  KI+ 
1.5  gram  I  in  60  c.c.  of  water)  drop  by  drop  until  iodine  begins  to 
precipitate. 

Kraut's  Reagent.4 — Dissolve  272  grams  of  potassium  iodide  in 
water  and  add  80  grams  of  bismuth  subnitrate  dissolved  in  200  grams 
of  nitric  acid  (sp.  gr.  -1.18).  Permit  the  potassium  nitrate  to  crystallize 
out,  then  filter  it  off  and  make  the  filtrate  up  to  i  liter  with  water. 

Lead  Acetate,  Basic.     (See  Basic  Lead  Acetate.) 

Litmus-Milk  Powder.5 — Add  i  part  of  powdered  litmus  to  50 
parts  of  dried  milk  powder.  To  make  a  litmus  milk  solution  add 
i  part  of  this  powder  to  9  parts  of  water. 

LugoFs  Solution.6 — Dissolve  4  grams  of  iodine  and  6  grams  of  potas- 
sium iodide  in  100  c.c.  of  distilled  water. 


1  Determination  of  acetone,  p.  557. 
*  Iodine  test,  p.  43. 

3  Amyloid  formation,  p.  48. 

4  Rosenheim's  bismuth  test  for  choline,  p.  375. 
6  Test  for  Lipase,  p.  197. 

6  Gunning's  iodoform  test,  p.  451. 


REAGENTS   AND    SOLUTIONS  637 

Lyle-Curtman  Guaiac  Reagent. — Fifty  gin.  of  the  ground  crude  gum 
guaiac  are  treated  in  a  beaker  with  20  gm.  of  KOH  dissolved  in  200 
c.c.  of  water.  After  thorough  stirring,  the  mixture  is  filtered  with 
the  aid  of  suction  through  cotton  spread  out  in  a  thin  layer  in  a  Buchner 
funnel.  The  residue  is  washed  with  water  until  the  combined  filtrate 
and  washings  approximate  1.5  liters.  To  the  dilute  KOH  solution  are 
added  with  constant  stirring  21  c.c.  of  glacial  acetic  acid  which  is  run 
dropwise  from  a  burette.  The  precipitate  is  allowed  to  settle,  the 
supernatant  liquid  poured  off,  and  the  residue  washed  once  with  water 
by  decantation.  The  precipitate  is  then  transferred  to  a  Buchner 
funnel  and  dried  by  suction  as  much  as  possible.  The  precipitate  is 
gently  heated  (small  portions  at  a  time)  in  an  evaporating  dish  when 
most  of  the  water  separates  and  is  removed  by  filter  paper.  After  the 
removal  of  the  water,  and  while  the  mass  is  still  plastic,  it  is  drawn  out 
into  thin  sheets.  In  this  condition  the  material  rapidly  hardens  and 
dries  in  the  air.  The  dried  masses  are  then  ground,  treated  with  300 
c.c.  of  hot  95  per  cent  alcohol  and  the  mixture  is  thoroughly  stirred  to 
prevent  the  formation  of  a  gummy  mass.  In  a  few  minutes  a  dark 
brown  material  separates  in  a  flocculent  condition.  This  is  filtered  off 
and  the  alcohol  removed  from  the  solution  by  distillation.  The  residue 
in  the  flask  is  treated  with  20  gm.  of  KOH  dissolved  in  water,  diluted 
considerably,  and  precipitated  as  before  with  about  20  c.c.  of  glacial 
acetic  acid.  The  precipitate  is  filtered  off  and  dried  as  described  above, 
after  which  it  is  ground  and  kept  in  a  desiccator.  The  weight  of  the 
material  finally  obtained  represents  a  yield  of  about  60  per  cent.  The 
time  required  to  make  this  preparation  is  4  hours,  the  distillation  of 
the  alcohol  being  the  most  time-consuming  of  all  the  operations. 

A  solution  containing  i  gm.  of  this  preparation  in  60  c.c.  of  95  per 
cent  alcohol  may  be  prepared  and  kept  in  a  glass-stoppered  bottle  of 
colorless  glass.  This  reagent  does  not  deteriorate  for  several  weeks. 

Magnesia  Mixture.1 — Dissolve  175  grams  of  magnesium  sulphate 
and  350  grams  of  ammonium  chloride  in  1400  c.c.  of  distilled  water. 
Add  700  grams  of  concentrated  ammonium  hydroxide,  mix  thoroughly, 
and  preserve  the  mixture  in  a  glass-stoppered  bottle. 

Magnesium  Nitrate  Solution  for  Ignition.2 — Dissolve  320  grams  of 
calcined  magnesia  in  nitric  acid,  avoiding  an  excess  of  the  latter;  then 
add  a  little  calcined  magnesia  in  excess;  boil;  filter  from  the  excess  of 
magnesia,  ferric  oxide,  etc.,  and  dilute  with  water  to  2  liters. 

Methyl  Red.3 — Saturated  solution  in  50  per  cent  alcohol. 

1  Method  for  determination  of  total  phosphorus,  p.  571. 

2  Determination  of  phosphorus,  p.  570. 

3  Determination  of  H  ion  concentration,  pp.  158  and  501 


638  PHYSIOLOGICAL  CHEMISTRY 

Methyl  Orange.1 — Dissolve  o.i  gm.  of  methyl  orange  in  100  c.c.  of 
distilled  water. 

Millon's  Reagent.2 — Digest  i  part  (by  weight)  of  mercury  with 
2  parts  (by  weight)  of  nitric  acid  (sp.  gr.  1.42)  and  dilute  the  resulting 
solution  with  2  volumes  of  water. 

Molisch's Reagent3 — A  15  per  cent  alcoholic  solution  of  a-naphthol. 

Molybdate  Solution.4 — Dissolve  100  grams  of  molybdic  acid  in  144 
<:.c.  of  ammonium  hydroxide  (sp.  gr.  0.90)  and  271  c.c.  of  water;  slowly 
and  with  constant  stirring  pour  the  solution  thus  obtained  into  489  c.c. 
of  nitric  acid  (sp.  gr.  1.42)  and  1148  c.c.  of  water.  Keep  the  mixture  in 
a  warm  place  for  several  days,  or  until  a  portion  heated  to  40° C.  deposits 
no  yellow  precipitate  of  ammonium  phosphomolybdate.  Decant  the 
solution  from  any  sediment  and  preserve  in  glass-stoppered  bottles. 

Morner's  Reagent.5- — Thoroughly  mix  i  volume  of  formalin,  45 
volumes  of  distilled  water,  and  55  volumes  of  concentrated  sulphuric 
acid. 

a-Naphthol  Solution.6 — Dissolve  i  gram  of  a-naphthol  in  100  c.c.  of 
95  per  cent  alcohol. 

Nessler's  Reagent.7 — (a)  Formula  of  Folin  and  Wu.  Nessler's 
solution  is  an  alkaline  solution  of  the  double  iodide  of  mercury  and 
potassium  (HgI2  2KI).  Introduce  into  a  500  c.c.  Florence  flask 
150  gm.  potassium  iodide  and  no  gm.  of  iodine;  add  100  c.c.  of  water 
and  an  excess  of  metallic  mercury,  140-150  gm.  Shake  the  flask 
continuously  and  vigorously  for  7-15  minutes  or  until  the  dissolved 
iodine  has  nearly  all  disappeared.  The  solution  becomes  quite  hot. 
When  the  red  iodine  solution  has  begun  to  become  visibly  pale,  though 
still  red,  cool  in  running  water  and  continue  the  shaking  until  the 
reddish  color  of  the  iodine  has  been  replaced  by  the  greenish  color  of 
the  double  iodide.  The  whole  operation  does  not  usually  take  more 
than  15  minutes.  Decant  the  solution,  washing  mercury  and  flask 
with  liberal  quantities  of  distilled  water.  Dilute  solution  and  washings 
to  2  liters.  -  If  the  cooling  was  begun  in  time  the  resulting  reagent  is 
clear  enough  for  immediate  dilution  with  10  per  cent  alkali  and  water 
and  the  finished  solution  can  be  used  at  once  for  Nesslerization.  From 
this  stock  solution  of  potassium  mercuric  iodide  prepare  final  Nessler's 
solutions  as  follows:  Introduce  into  a  flask  of  at  least  5  liters  capacity, 
3500  c.c.  of  10  per  cent  sodium  hydroxide  solution,  add  750  c.c.  of  the 

1  Determination  of  urea  in  urine,  p.  518. 

2  Millon's  reaction,  p.  97. 

3  Molisch's  reaction,  p.  21. 

4  Detection  and  determination  of  phosphorus,  pp.  128  and  571. 

6  Morner's  test,  p.  85. 

8  Oxidases  p.  15.     For  other  a-naphthol  solution  see  Molisch  reaction. 

7  Determination  of  nitrogen  pp.  278,  279  and  508. 


REAGENTS  AND   SOLUTIONS  639 

double  iodide  solution  and  750  c.c.  of  distilled  water,  making  5  liters 
of  solution.  The  10  per  cent  NaOH  should  be  made  from  a  saturated 
solution  (containing  about  55  gm.  per  100  c.c.)  which  has  been  allowed 
to  stand  until  the  carbonate  has  settled,  the  clear  solution  being  de- 
canted and  used.  This  solution  should  have  been  standardized  with 
an  accuracy  of  at  least  5  per  cent. 

(b)  Formula  of  Bock  and  Benedict. — Place  100  gm.  mercuric  iodide 
and  70  gm.  potassium  iodide  in  a  liter  volumetric  flask  and  add  about 
400  c.c.  of  water.  Rotate  until  solution  is  complete.  Now  dissolve 
100  gm.  NaOH  in  about  500  c.c.  of  water,  cool  thoroughly  and  add 
with  constant  shaking  to  the  mixture  in  the  flask,  then  make  up  with 
water  to  the  liter  mark.  This  usually  becomes  perfectly  clear.  When 
the  small  amount  of  brownish  red  precipitate  which  forms,  settles  out 
the  supernatant  fluid  is  ready  to  be  poured  off  and  used. 

Neutral  Olive  Oil.1 — Shake  ordinary  olive  oil  with  a  10  per  cent 
solution  of  sodium  carbonate,  extract  the,  mixture  with  ether,  and 
remove  the  ether  by  evaporation.  The  residue  is  neutral  olive  oil. 

Neutral  Red.2 — A  i  per  cent  solution  in  50  per  cent  alcohol. 

p-Nitrophenol.2 — A  i  per  cent  solution  in  50  per  cent  alcohol. 

Nylander's  Reagent.3 — Digest  2  grams  of  bismuth  subnitrate 
and  4  grams  of  Rochelle  salt  in  100  c.c.  of  a  10  per  cent  solution 
of  potassium  hydroxide.  The  reagent  should  then  be  cooled  and 
filtered. 

Obermayer's  Reagent.4 — Add  2-4  grams  of  ferric  chloride  to  a 
liter  of  hydrochloric  acid  (sp.  gr.  1.19). 

Oxalated Plasma.5 — Allow  arterial  blood  to  run  into  an  equal  volume 
of  0.2  per  cent  ammonium  oxalate  solution. 

Para-dimethylaminobenzaldehyde  Solution.6 — This  solution  is 
made  by  dissolving  5  grams  of  para-dimethylaminobenzaldehyde  in 
100  c.c.  of  10  per  cent  sulphuric  acid. 

Para-phenylenediamine  Hydrochloride  Solution.7— Two  grams  dis- 
solved in  ico  c.c.  of  water. 

Permutit.8 — A  synthetic  aluminium  silicate  obtained  from  the 
Permutit  Company,  New  York.  Only  such  preparations  as  have 
passed  through  a  60  mesh  sieve  and  do  not  pass  through  an  80  mesh 
sieve  should  be  used.  It  should  give  off  very  little  dust  or  turbid 

1  Einulsification  of  fats,  p.  183. 

2  Determination  of  H  ion  concentration,  pp.  161  and  501. 

3  Nylander's  test,  pp.  28  and  436. 

4  Obermayer's  test,  p.  405. 

5  Experiments  on  blood  plasma,  p.  271. 

6  Herter's  para-dimethylaminobenzaldehyde  reaction,  p,   222. 

7  Detection  of  hydrogen  peroxide,  p.  341. 

8 Determination  of  ammonia  and  urea  in  urine,  pp.  516  and  522. 


640  PHYSIOLOGICAL  CHEMISTRY 

material  to  water  and  settle  in  a  few  seconds.  It  may  be  used  more 
than  once  by  washing  first  with  water,  then  with  2  per  cent  acetic  acid 
and  finally  with  water  again. 

Peters'  Sugar  Reagents.1 — (a)  Copper  Solution. — Dissolve  34.639 
grams  of  highest  purity  crystallized  copper  sulphate  (such  as  Kahl- 
baum's  "zur  analyse  mit  garantieschein ")  in  water  to  make  500  c.c. 

(b)  Alkaline   Tartrate  Solution. — Dissolve   173   grams   of  sodium 
potassium  tartrate  and  125  grams  of  potassium  hydroxide  in  water  to 
make  500  c.c. 

(c)  N/$  Sodium  Thiosulphate. — Dissolve  about  50  grams  of  ordinary 
c.p.  sodium  thiosulphate  or  exactly  49.66  grams  of  the, pure,  dry, 
recrystallized  salt,  in  enough  boiled  out  distilled  water  to  make  a 
liter.    Allow  to  stand  for  several  days.    The  solution  should  be  stand- 
ardized against  the  copper  solution  prepared   as   above.     For  this 
purpose  introduce  20  c.c.  of  the  copper  solution  into  a  200  c.c.  Erlen- 
meyer  flask,  add  20  c.c.  of  strong  acetic  acid  (30  per  cent)  and  40  c.c.  of 
water.     Add  about  7  grams  of  a  saturated  solution  of  KI  and  titrate 
with  the  thiosulphate  using  starch  as  an  indicator.     Calculate  the 
equivalent  of  i  c.c.  of  thiosulphate  in  Cu.     One  c.c.  of  the  copper 
sulphates  solution  contains  17.647  mg.  of  Cu.     The  thiosulphate  remains 
constant  for  some  months.     It  should  be  kept  in  a  dark  bottle. 

Phenolphthalein.2 — Dissolve  i  gram  of  phenolphthalein  in  100  c.c. 
of  95  per  cent  alcohol. 

Permanganate  Solution  (Alkaline)  for  Van  Slyke  Method.3— The 
alkaline  permanganate  solution  contains  50  grams  of  potassium  per- 
manganate and  25  grams  of  potassium  hydroxide  per  liter. 

Potassium  Permanganate  Standard  (N/io)  Solution. — Dissolve 
3.162  grams  of  pure  potassium  permanganate  in  a  liter  of  distilled 
water,  allow  to  stand  a  few  days,  and  filter  through  glass  wool.  Stand- 
ardize against  N/io  oxalic  acid  solution  or  against  pure  dry  sodium  or 
potassium  oxalate.  One  c.c.  of  N/io  permanganate  is  equivalent  to 
7.0  mg.  of  sodium  oxalate. 

Phenylhydrazine  Mixture.4 — This  mixture  is  prepared  by  com- 
bining 2  parts  of  phenylhydrazine-hydrochloride  and  3  parts  of  sodium 
acetate  by  weight.  These  are  thoroughly  mixed  in  a  mortar. 

Phenylhydrazine-Acetate  Solution.5 — This  solution  is  prepared  by 
mixing  i  volume  of  glacial  acetic  acid,  i  volume  of  water,  and  2  volumes 
of  phenylhydrazine  (the  base.) 

1  Determination  of  sugar,  p.  543. 
9  Topfer's  method,  p.  177. 

3  Determination  of  ammo-acid  nitrogen,  p.  87. 

4  Phenylhydrazine  reaction,  pp.  22  and  431. 

5  Phenylhydrazine  reaction,  pp.  22  and  431. 


REAGENTS   AND   SOLUTIONS  641 

Picramic  Acid. — Permanent  Standard  for  Lewis-Benedict  Blood  Sugar 
Method* — A  solution  of  picramic  acid  makes  a  very  satisfactory 
permanent  standard. .  The  color  is  identical  in  quality  with  that  formed 
in  the  method  and  its  solution  keeps  perfectly.  The  formula  of  the 
permanent  standard  is: 

Picramic  acid o .  064  gram. 

Sodium  carbonate  (anhydrous)  o.  100  gram. 

Water  to  make 1000.0      c.c. 

Dissolve  the  picramic  acid  with  the  aid  of  heat  in  25-50  c.c.  of  distilled 
water  which  has  been  made  alkaline  with  sodium  carbonate.  Cool  and 
dilute  to  i  liter.  This  solution  has  the  same  intensity  of  color  as  that 
obtained  by  the  proposed  method  with  0.64  mg.  of  sugar  when  the 
final  volume  of  the  reaction  fluid  is  made  10  c.c.  The  solution  should 
be  standardized  against  pure  glucose.  A  satisfactory  preparation  .of 
picramic  acid  may  be  obtained  from  the  J.  T.  Baker  Chemical  Co., 
Phillipsburg,  N.  J. 

Picric  Acid,  Pure.2 — As  purchased  picric  acid  contains  10  per  cent 
of  added  water.  By  exposure  to  the  air  between  large  filter  papers 
(best  in  a  warm  place)  the  water  will  disappear  by  evaporation.  Dry 
picric  acid  may  be  prepared  in  this  way.  If  the  alkaline  picrate  formed 
from  this  acid  gives  too  deep  a  color,  it  may  be  purified  as  follows: 

(a)  Method  of  Folin  and  Doisy. — Transfer  about  600  gm.  of  wet 
picric  acid,  or  about  a  pound  of  dry  picric  acid,  to  a  large  beaker 
(capacity  not  less  than  4  liters).  Pour  on  boiling  water  until  the 
beaker  is  nearly  full  and  add  200  c.c.  of  saturated  (50  per  "cent)  sodium 
hydroxide  solution.  Stir,  and  if  necessary  heat  again  until  all  the 
picric  acid  has  been  dissolved,  yielding  a  deep  red  picrate  solution. 
To  the  hot  solution  add  rather  slowly,  with  stirring,  200  gm.  of  sodium 
chloride.  Cool  in  running  water  to  about  3O°C.,  with  occasional 
stirring.  Filter  on  a  large  Buchner  funnel  and  wash  a  few  times  with 
5  per  cent  sodium  chloride  solution.  Transfer  the  picrate  to  a  large 
beaker,  fill  with  boiling  water,  and  when  the  picrate  is  dissolved  add, 
with  stirring,  first  50  c.c.  of  10  per  cent  sodium  hydroxide  solution,  and 
then  100  gm.  of  sodium  chloride.  Cool  to  3o°C.,  with  stirring,  filter, 
and  wash  with  sodium  chloride  solution,  as  before.  Repeat  the  solu- 
tion and  precipitation  of  the  sodium  picrate  once  more,  but  for  the 
last  washing  of  the  last  precipitated  picrate  use  distilled  water  instead 
of  the  sodium  chloride  solution. 

Dissolve  the  purified  picrate  in  the  same  large  beaker  with  boiling 
distilled  water,  and  filter  while  hot  on  a  large  folded  filter,  collecting 

1  Determination  of  sugar  in  blood,  p.  287. 

2  Determination  of  creatinine  p.  280,  and  calcium  p.  293,  in  blood. 


642  PHYSIOLOGICAL  CHEMISTRY 

the  filtrate  in  a  large  flask.  To  the  hot  filtrate  add  100  c.c.  of  concen- 
trated sulphuric  acid,  previously  diluted  with  about  two  volumes  of 
water.  The  liberated  picric  acid  begins  to  come  out  at  once.  Put  a 
beaker  over  the  mouth  of  the  flask  and  cool  under  running  tap  water  to 
about  3o°C.  Filter  with  suction  as  before  and  wash  free  from  sul- 
phates with  distilled  water. 

(b)  Method  of  Halverson  and  Bergeim. — To  50  gm.  of  picric  acid  add 
700  c.c.  of  distilled  water.  Boil  until  clear  and  while  boiling  add 
10  c.c.  of  concentrated  hydrochloric  acid.  Cool.  Wash  by  decanta- 
tion  with  100  c.c.  of  distilled  water.  Repeat  the  recrystallization. 
Transfer  to  a  Buchner  funnel  and  wash  with  about  150  c.c.  of  water. 
Dry  in  a  desiccator  or  between  filter  papers. 

Picric  Acid,  Saturated  Solution.1 — This  may  be  prepared  either  by 
allowing  distilled  water  to  stand  in  contact  with  an  excess  of  picric 
acid  with  occasional  shaking,  or  by  making  a  1.2  per  cent  solution. 

Picric  Acid  and  Sodium  Picrate  Solution.2 — Place  36  gm.  dry  pow- 
dered picric  acid  in  a  liter  flask  or  stoppered  cylinder,  add  500  c.c.  of 
i  per  cent  sodium  hydroxide  solution  and  400  c.c.  of  hot  water.  Shake 
occasionally  until  dissolved.  Cool  and  dilute  to  one  liter. 

Roberts'  Reagent.3 — Mix  i  volurhe  of  concentrated  nitric  acid  and 
5  volumes  of  a  saturated  solution  of  magnesium  sulphate. 

Rosenheim's  lodo-Potassium  Iodide  Solution.4— Dissolve  2  grams 
ofiodine  and  6  grams  of  potassium  iodide  in  100  c.c.  of  water. 

Sahli's  Reagent.6 — This  reagent  consists  of  a  mixture  of  equal  parts 
of  a  48  per  cent  solution  of  potassium  iodide  and  an  8  per  cent  solution  of 
potassium  iodate. 

Salted  Plasma.6 — Allow  arterial  blood  to  run  into  an  equal  volume 
of  a  saturated  solution  of  sodium  sulphate  or  a  10  per  cent  solution  of 
sodium  chloride.  Keep  the  mixture  in  the  cold  room  for  about  24 
hours. 

Schweitzer's  Reagent.7 — Add  potassium  hydroxide  to  a  5  per  cent 
solution  of  copper  sulphate  which  contains  5  per  cent  ammonium 
chloride.  Filter  off  the  precipitate  of  cupric  hydroxide,  wash  it,  and 
bring  3  grams  of  the  moist  cupric  hydroxide  into  solution  in  a  liter  of 
20  per  cent  ammonium  hydroxide. 

Seliwanoff's  Reagent.8 — Dissolve  0.05  gram  of  resorcinol  in  100  c.c. 
of  dilute  (1:2)  hydrochloric  acid. 

1  Determination  of  creatinine  in  blood  p.  280  and  urine  p.  526.     Also  qualitative  tests. 

2  Determination  of  sugar  in  blood  p.  287. 

3  Roberts'  ring  test,  pp.  103  and  440. 

4  Rosenheim's  periodide  test,  p.  374 
6  Determination  of  free  acid,  p.  167. 

6  Experiments  on  blood  plasma,  p.  271. 

7  Schweitzer's  solubility  test,  p.  48. 

8  Seliwanoff's  reaction,  pp.  34  and  462. 


REAGENTS  AND   SOLUTIONS  643 

Silver  Nitrate  Solution.1 — Dissolve  29.042  grams  of  silver  nitrate  in 
i  liter  of  distilled  water.  Each  cubic  centimeter  of  this  solution  is 
equivalent  to  o.oi  gram  of  sodium  chloride  or  to  0.006  gram  of 
chlorine. 

Sodium  Acetate  Solution.2 — Dissolve  100  grams  of  sodium  acetate 
in  800  c.c.  of  distilled  water,  add  100  c.c.  of  30  per  cent  acetic  acid 
to  the  solution,  and  make  the  volume  of  the  mixture  up  to  i  liter  with 
distilled  water. 

Sodium  Alcoholate  (N/io)  Solution.3 — The  sodium  alcoholate  is 
made  by  dissolving  2.3  grams  of  cleaned  metallic  sodium  in  i  liter  of 
absolute  alcohol.  It  is  advisable  that  it  be  slightly  weaker  than  stronger 
than  tenth-normal.  It  may  be  standardized  against  pure  benzoic  acid 
in  washed  chloroform.  It  may  also  be  standardized  against  N/io  HC1 
provided  the  alcoholate  solution  contains  not  more  than  traces  of 
carbonate. 

Sodium  Alizarin  Sulphonate.4 — Dissolve- 1  gram  of  sodium  alizarin 
sulphonate  in  100  c.c.  of  water. 

Sodium  Hydroxide  Saturated  Solution.5— Shake  up  about  120  gm. 
of  best  quality  NaOH  with  100  c.c.  of  distilled  water  in  a  300  c.c. 
Erlenmeyer  flask  (Pyrex).  Stopper  and  allow  to  stand  for  a  couple  of 
days  or  until  the  sodium  carbonate  settles  to  the  bottom  leaving  a 
clear  solution  of  NaOH  practically  free  from  carbonate,  and  containing 
about  55  gm.  NaOH  per  100  c.c. 

Sodium  Sulphide  Solution.6 — Saturate  a  i  per  cent  solution  of 
sodium  hydroxide  with  hydrogen  sulphide  gas  and  add  an  equal  volume 
of  i  per  cent  sodium  hydroxide. 

Sodium  Thiosulphate  Standard  (N/io)  Solution.7 — Weigh  out  25 
grams  of  ordinary  c.p.  sodium  thiosulphate  or  24.83  grams  of  the  pure 
dry  recrystallized  salt.  Dissolve  in  water  and  dilute  to  a  liter.  Boiled 
distilled  water  must  be  used.  Keep  in  a  bottle  with  a  siphon  arrange- 
ment and  carrying  a  soda  lime  tube  to  exclude  C02. 

It  is  best  standardized  against  acid  potassium  iodate  KH(IOs)2. 
Weigh  out  accurately  0.3249  gram  of  acid  potassium  iodate.  Dissolve 
in  50  c.c.  of  water,  heating  gently  if  necessary.  Transfer  the  solution  to 
a  100  c.c.  flask,  rinsing  the  beaker  carefully  and  make  to  mark  with 
water.  This  solution  is  exactly  decinormal.  Pipette  out  25  c.c.  into  an 

1  Volhard-Arnold  method,  p.  572. 

1  Uranium  acetate  method,  p.  568 

1  Determination  of  hippuric  acid,  p.  537. 

4  Topfer's  method,  p.  177. 

'Preparation  of  standard  alkali  and  Nessler's  solution  pp.  497,  508. 

'  Kriiger  and  Schmidt's  method,  p.  533. 

7  Determination  of  acetone,  p.  557. 


644  PHYSIOLOGICAL  CHEMISTRY 

Erlenmeyer  flask,  add  i  gram  of  potassium  iodide  dissolved  in  a 
little  water,  and  a  few  cubic  centimeters  of  dilute  hydrochloric  acid. 
Titrate  immediately  with  the  thiosulphate  solution.  When  the  solution 
becomes  pale  yellow  add  a  few  cubic  centimeters  of  i  per  cent  solu- 
tion of  soluble  starch  and  titrate  to  loss  of  blue  color. 

Sodium  Tungstate  Solution.1 — A  10  per  cent  solution  of  sodium 
tungstate  in  water.  Some  sodium  tungstates  though  labeled  c.p.  are 
not  serviceable  for  this  work.  They  usually  contain  too  much  sodium 
carbonate.  The  c.p.  sodium  tungstate  made  by  the  Primes  Chemical 
Co.,  Primos,  Pa.,  is  satisfactory. 

Solera's  Test  Paper.2 — Saturate  a  good  quality  of  filter  paper  with 
0.5  per  cent  starch  paste  to  which  has  been  added  sufficient  iodic  acid 
to  make  a  i  per  cent  solution  of  iodic  acid  and  allow  the  paper  to  dry 
in  the  air.  Cut  it  in  strips  of  suitable  size  and  preserve  for  use. 

Spiegler's  Reagent.3 — This  reagent  has  the  following  composition: 

Tartaric  acid 20  grams. 

Mercuric  chloride 40  grams. 

Sodium  chloride 50  grams. 

Glycerol 100  grams. 

Distilled  water. 1000  grams. 

Starch  Iodide  Solution.4 — Mix  o.i  gram  of  starch  powder  with 
cold  water  in  a  mortar  and  pour  the  suspended  starch  granules  into  75- 
100  c.c.  of  boiling  water,  stirring  continuously.  Cool  the  starch  paste, 
add  20-25  grams  of  potassium  iodide  and  dilute  the  mixture  to  250  c.c. 
This  solution  deteriorates  upon  standing,  and  therefore  must  be  freshly 
prepared  as  needed. 

Starch  Paste.' — Grind  2  grams  of  starch  powder  in  a  mortar  with  a 
small  amount  of  water.  Bring  200  c.c.  of  water  to  the  boiling-point  and 
add  the  starch  mixture  from  the  mortar  with  continuous  stirring.  Bring 
again  to  the  boiling-point  and  allow  it  to  cool.  This  makes  an  approxi- 
mate i  per  cent  starch  paste  which  is  a  very  satisfactory  strength  for 
general  use. 

Stokes'  Reagent.5 — A  solution  containing  2  per  cent  ferrous  sulphate 
and  3  per  cent  tartaric  acid.  When  needed  for  use  a  small  amount 
should  be  placed  in  a  test-tube  and  ammonium  hydroxide  added  until 
the  precipitate  which  forms  on  the  first  addition  of  the  hydroxide  has 
entirely  dissolved.  This  produces  ammonium  ferrotartrate,  which  is  a 
reducing  agent. 

1  Preparation  of  protein-free  blood  filtrate,  p.  276. 

2  Solera's  reaction,  p.  58. 

3  Spiegler's  ring  test,  pp.  103  and  440. 

4  Fehling's  method,  p.  542. 

5  Hemoglobin,  p.  301.    Hemochromogen,  p.  302 


REAGENTS  AND   SOLUTIONS  645 

Sulphuric  Acid,  Two-thirds  Normal.1 — Dilute  35  gm.  of  concen- 
trated c.p.  sulphuric  acid  to  a  liter.  Standardize  against  alkali  of 
known  strength. 

Sulphuric-Phosphoric  Acid  Digestion  Mixture.2 — To  50  c.c.  of 
5  per  cent,  copper  sulphate  solution  add  300  c.c.  of  85  per  cent  phos- 
phoric acid  and  mix.  Add  100  c.c.  of  concentrated  sulphuric  acid 
free  from  the  least  trace  of  ammonia  and  mix.  Keep  well  protected  to 
prevent  absorption  of  ammonia  from  the  air. 

Suspension  of  Manganese  Dioxide.3 — Made  by  heating  a  o.-  per 
cent  solution  of  potassium  permanganate  with  a  little  alcohol  until  it  is 
decolorized. 

Tanrefs  Reagent.4 — Dissolve  1.35  grams  of  mercuric  chloride  in 
25  c.c.  of  water,  add  to  this  solution  3.32  grams  of  potassium  iodide 
dissolved  in  25  c.c.  of  water,  then  make  the  total  solution  up  to  60  c.c. 
with  distilled  water  and  add  20  c.c  of  glacial  acetic  acid  to  the  mixture. 

Tincture  of  Iodine. — Dissolve  70  gram's  of  iodine  and  50  grams  of 
potassium  iodide  in  i  liter  of  95  per  cent  alcohol. 

Topfer's  Reagent.5 — Dissolve  0.5  gram  of  di-methylaminoazobenzene 
in  100  c.c.  of  95  per  cent  alcohol. 

Tropaeolin  OO.6 — Dissolve  0.05  gram  of  tropseolin  00  in  100  c.c. 
of  50  per  cent  alcohol. 

Uffelmann's  Reagent.7 — Add  a  5  per  cent  solution  of  ferric  chloride 
to  a  i  per  cent  solution  of  carbolic  acid  until  an  amethyst-blue  color  is 
obtained. 

Uranium  Acetate  Solution.8 — Dissolve  about  35.0  grams  of  uranium 
acetate  in  i  liter  of  water  with  the  aid  of  heat  and  3-4  c.c.  of  glacial 
acetic  acid.  Let  stand  a  few  days  and  filter.  Standardize  against  a 
phosphate  solution  containing  0.005  gram  of  f^O&  per  cubic  centimeter. 
For  this  purpose  dissolve  14.721  grams  of  pure  air-dry  sodium  am1 
monium  phosphate  (NaNH4HP04+4H20)  in  water  to  make  a  liter. 
To  20  c.c.  of  this  phosphate  solution  in  a  200  c.c.  beaker  add  30  c.c. 
of  water  and  5  c.c.  of  sodium  acetate  solution  (see  above)  and 
titrate  with  the  uranium  solution  to  the  correct  end  reaction  as  indi- 
cated in  the  method  proper,  page  572.  If  exactly  20  c.c.  of  uranium 
solution  are  required  i  c.c.  of  the  solution  is  equivalent  to  0.005  gram 

"^Preparation  of  protein-free  blood  nitrates,  p.  276 

2  Determination  of  nitrogen,  p.  277  and  507. 

3  Kriiger  and  Schmidt's  method,  p.  533 . 

4  Tanret's  test,  p.  103. 

5  Topfer's  method,  p.  177. 

6  Test  for  free  acid,  p.  158. 

7  Uffelmann's  reaction,  p.  173. 

8  Phosphate  determination,  p.  568. 


646  PHYSIOLOGICAL  CHEMISTRY 

PzOs.     If  stronger  than  this  dilute  accordingly  and  check  again  by 
titration. 

Urease.1 — (a)  Soy  Bean  Meal.— Grind  the  soy  bean  to  a  powder 
which  will  pass  through  a  2o-mesh  sieve. 

(b)  Solid  Urease  Preparation. — Digest  i  part  of  soy  bean  meal  with 
5  parts  of  water  at  room  temperature,  with  occasional  stirring  for  an 
hour,  and  clear  the  solution  by  filtration  through  paper  pulp  or  centri- 
fugation.    Pour  this  extract  slowly,  with  stirring,  into  at  least  10  volumes 
of  acetone.     The  acetone  dehydrates  the  enzyme  preparation.     Filter, 
dry  in  vacuum  and  powder.     For  standardization  procedure  see  the 
determination  of  urea  in  urine. 

(c)  Enzyme  Solution. — Dissolve  2  grams  of  urease,  prepared  as  above, 
together  with  0.6  gram  of  di-potassium-hydrogen  phosphate  and  0.4 
gram  of  mono-potassium-dihydrogen  phosphate  "in  10  c.c.  of  water. 
The  solution  may  be  kept  under  toluene  for  two  weeks,  without  losing 
activity. 

(d)  Alcoholic  Urease  Solution. — Place  3  grams  of  permutit  in  a  flask, 
wash  once  with  2  per  cent  acetic  acid,  then  twice  with  water;  add  5 
grams  of  fine  jack  bean  meal  and  100  c.c.  of  30  per  cent  alcohol.     Shake 
gently  but  continuously  for  10  to  15  minutes  and  filter.     The  filtrate 
contains  practically  all  of  the  urease  and  extremely  little  of  other 
materials. 

Uric  Acid  Reagents.2 — (a)  Silver  Lactate  Solution. — A  solution  of 
5  per  cent  silver  lactate  in  5  per  cent  lactic  acid. 

(b)  Standard   Uric  Acid  Solution. — In  a   500   c.c.   flask  dissolve 
exactly  i  g.  of  uric  acid  in  150  c.c.  of  water  by  the  help  of  0.5  g.  lithium 
carbonate.     Dilute  to  500  c.c.  and  mix.     Transfer  50  c.c.  to  a  liter 
flask,  add. 500  c.c.  of  20  per  cent  sodium  sulphite  solution,  dilute  to 
volume  and  mix.     Each  c.c.  of  this  solution  is  then  equal  to  o.i  mg.  of 
uric  acid.     Transfer  to  small  bottles  (cap.  200  c.c.)  and  stopper  tightly. 
Thjs  standard  uric  acid  solution  keeps  almost  indefinitely  in  unopened 
bottles,  because  the  sulphite  prevents  the  spontaneous  oxidation  of 
the  .uric  acid.     In  used  bottles  the  standard  usually  remains  good  for 
2-3  months. 

(c)  Sodium  Carbonate  Solution. — Dissolve  200  grams  of  anhydrous 
sodium  carbonate  in  warm  water,  cool  and  dilute  to  i  liter. 

(d)  Uric  Acid  Reagent. — Introduce  into  a  flask  700  c.c.  of  water, 
100  g.  of  sodium  tungstate,  and  80  c.c.  of  phosphoric  acid  (85  per  cent. 
H3P04).     Partly  close  the  mouth  of  the  flask  with  a  funnel  and  a  small 
watch  glass  and  boil  gently  for  2  hours.     Dilute  to  i  liter. 

1  Determination  of  urea,  pp.  278,  285,  and  514. 
^Determination  of  uric  acid,  p.  281  and  p.  530. 


REAGENTS    AND    SOLUTIONS 


647 


(e)  A  5  per  cent  sodium  cyanide  solution. 

(/)  A  10  per  cent  solution  of  sodium  chloride  in  o.i  normal  hydro- 
chloric acid. 

(g)  A  10  per  cent  sodium  sulphite  solution,  kept  in  small,  tightly 
stoppered  bottles. 


INTERNATIONAL  ATOMIC  WEIGHTS,  1920 


Aluminium Al 

Antimony Sb 

Arsenic As 

Barium Ba 

Bismuth Bi 

Boron B 

Bromine Br 

Cadmium Cd 

Calcium Ca 

Carbon. C 

Chlorine Cl 

Chromium Cr 

Cobalt Co 

Copper Cu 

Fluorine F 

Glucinum Gl 

Gold 'Au 

Hydrogen H 

Iodine I 

Iridium Ir 

Iron Fe 

Lanthanum La 

Lead Pb 

Lithium Li 

Magnesium Mg 


=  16. 
27.1 

120.2 
74.96 

137-37 

208.0 
10.9 
79.92 

112.40 
40.07 
12.005 
35.46 
52.0 
58.97 
63.57 
I9.O 
9.1 

197.2 
1.008 

126.92 

IQ3.I 
55.84 

139.0 

2O7.2O 

6-94 
24.32 


0  =  16. 

Manganese Mn    54 . 93 

Mercury Hg  200 . 6 

Molybdenum Mo    96  .o 

Nickel < Ni      58.68 

Nitrogen N  14 . 008 

Osmium Os  190.9 

Oxygen O       16 .  oo 

Palladium Pd  106. 7 

Phosphorus P       31 . 04 

Platinum . .  Pt  195 . 2 

Potassium K       39. 10 

Radium Ra  226.0 

Selenium Se      79 . 2 

Silicon Si       28.3 

Silver Ag  107 . 88 

Sodium Na     23 .00 

Strontium Sr      87 . 63 

Sulphur S        32.06 

Tantalum Ta  181 . 5 

Tellurium Te  127.5 

Tin Sn  118.7 

Titanium Ti      48. i 

Tungsten W  184.0 

Uranium U  238.2 

Zinc Zn      65.37 


INDEX 


Main  references  are  in  heavy-faced  type, 

Abderhalden  test  for  pregnancy,  principle  of,  3        Acid,  diaminotrihydroxydodecanoic,  84 
Absorption  of  carbohydrate  as  influenced  by  fat 

ingestion,  602 

Acacia    solution,  formation  of  emulsion  by,  181 
Accessory  food  substances,  580 

influence  on  growth,  581 
Acetoacetic  acid,  273,  430,  453,  552,  556 

formula  for,  453 

Gerhardt's  test  for,  454 

Hurtley's  reaction  for,  454 

Le  Nobel  reaction  for,  453 

quantitative  determination  of,  553 
Acetone,  273,  430,  450,  552,  557 

bodies,  273,  327,  45o,  552,  557 

determination  of  in  urine,  552,  557 

Van  Slyke's  methods  for,  552 
origin  of,  306 

formula  for,  450 

Frommer's  test  for,  452 

Gunning's  iodoform  test  for,  451 

Legal's  nitroprusside  test  for,  452 

Lieben's  test  for,  452 

quantitative  determination  of,  552 
Acholic  stool,  226 
Achroo-dextrins,  42,  55 

a-achroo-dextrin,  55 

/8-achroo-dextrin,  55 

T-achroo-dextrin,  55 
Acid,  acetic,  353,  387,  415 

acetoacetic,  273,  327,  430,  453,  552,  557 

alloxyproteic,  386,  409 

amino-acetic,  64,  68,  70,  199 

amino-butyric,  217 

amino-ethyl-sulphonic,  207,  364 

a-amino-jS-hydroxy-propionic,  68,  72 

o-amino-0-imidazolyl-propionic,  67,  76 

a-amino-iso-butyl-acetic,  68,  78 

a-amino-j8-methyl-/3-ethyl-propionic,    67,    79 

a-amino-normal  glutaric,  68,  81 

a-amino-propionic,  67,  71 

amino-succinic,  68,  81 

amino-valeric,  217 

a-amino-iso- valeric  (see  Valine),  68,  77 

a-diamino-jS-dithiolactyl,  68,  74 

aspartic,  68,  81 

benzoic,  71,  386,  405,  412,  616,  619 

butyric,  8,  336,  340,  387,  415 

caproic,  329,  336 

carbamic,  250 

cholic,  207 

chondroitin-sulphuric,  364,  353,  386 

citric,  329 

combined  hydrochloric  (protein  salt),  55  139, 
176,  178,  632 

cyanuric,  390 

a-e-diamino-caproic,  67,  79 


diazo-benzene-sulphonic,  469 

ethereal  sulphuric,  215,  386,  402 

fatty,  179,  180,  185,  215,  387,  415 

formic,  25,  387,  415 

free  hydrochloric,  55,  139,  156,  165,  i?6,  177 

glucothionic,  484 

glutamic,  68,  81 

glycerophosphoric,  370,  371,  387,  416 

glycocholic,  207 

glycosuric,  412 

glycuromic,  35,  37,  434,  456 

glyoxylic,  98 

guanT&ine-a-amino-valeric,  67,  78 

hippuric,  71,  386,  405,  413,  480,  537.  619 

homogentisic,  26,  386,  411,  434 

hydrochloric,  N/io,  498 

0-hydroxybutyric,   273,  327,  3<>6,  310,    43<>. 

453,  455,  552 

hydroxymandelic,  386,  411 
iminazolylpropionic,  217 
indole-a-amino-propionic,  67,  76 
indolylacetic,  217,  467 
indoxyl-sulphuric,  215,  386,  402,  403 
inosinic,  358,  364 
_  iso valeric,  217 
kynurenic,  386,  412 
lactic,  39,  139,  162,  172,  330,  358,  359 
lauric,  329 

•mucic,  35,  39,  450,  460 
myristic,  329 

nucleic,  93,  122,  123,  129-132 
osmic,  373 
oxalic,  386,  408,  562 
oxalic,  N/io,  496,  497 
oxaluric,  386,  414 

oxy-a-pyrrolidine-carboxylic,  67,  84 
oxyproteic,  386,  409,  469,  568 
palmitic,  179,  180,  184,  185 
para-cresolesulphuric,  386,  402 
para  hydroxyphenyl-acetic,  215,  217,  386,411 
para  -  hydro xy  -  0  -  phenyl  -  a  -  amino  -  propionic, 

68,  73.  85 
para-hydroxyphenyl-propionic,  216,  218,  397, 

411 

paralactic,  250,  330,  359.  387,  4*5 
phenaceturic,  387,  416 
phenol-sulphuric,  387,  402 
phenylacetic,  217 
phenyl-a-amino  propionic,  68,  72 
phenylpropionic,  217 
phosphocarnic,  358,  387,  416 
phosphoric,  424 

pyrocatechin-sulphuric,  386,  402 
a-pyrrolidine-carboxylic,  67,  84 
sarcolactic,  359 


649 


650 


INDEX 


Acid,  skatole  acetic,  76 

skatole  carbonic  220,  223 

skatoxyl-sulphuric,  386,  403 

stearic,  180,  371 

succinic,  217 

sulphanilic,  469 

tannic,  44,  47,  102 

taurocholic,  207 

trichlorethylglucuronic,  434 

uric,  25,   126,  250,  273,  281,  358,  386,  388, 

394,  477,  493.  494.  S3O 
urocanic,  387,  416 
uroferric,  386,409 
uroleucic,  386 

volatile  fatty,  215,  218,  387,  415 
Acid  albuminate.     See  Acid  metaprotein. 
Acid  excretion  in  urine,  determination  of  index 

of,  324 
Acid-forming  foods,  influence  of  on  hydrogen  ion 

concentration  of  urine,  613 
Acid-4iematin,  257,  272,  303 
Acid    infraprotein.     See    Acid    metaprotein. 
Acid  metaprotein,  94,  114,  115 
coagulation  of,  115 
experiments  on,  115 
precipitation  of,  115 
preparation  of,  115 
solubility  of,  115 
sulphur  content  of,  115 
Acidimetry,  496 

Acidity  of  gastric  juice,  quantitative  determina- 
tion of,  150,  162,  165 
urine,  cause  of,  378,  424 

quantitative  determination  of,  by  hy- 
drogen ion  concentration,  500 
by  titration,  499 
Acidosis,  304,  450,  609 
blood  in,  273 
general  discussion  of,  304 
metabolism  in,  609 
Acrolein,  formation  of,  from  olive  oil,  183 

from  glycerol,  186 
Activation,  6,  190 
Activation  of  calcium  salts,  190 
Adam's  paper  coil  method  for  determination  of 

fat  in  milk,  343 
Adaptation,  56 
Adenase  4,  126 

Adenine,    4,   124,   125,   126,   131,  364,  387,  419 
Adipocere,  182 
Adipose  tissue,  356 
Agar-agar,  20,  49,  227,  618,  622 
Agglutination.  253,  265 
Alanine,  67,  71,  217 
Albino  rats,  experiments  on,  580 
Albumin,  egg,  93,  105,  106 

crystallized,  preparation  of,  105 
powdered,  preparation  of,  106 

tests  on,  106 

serum,  92,  249,  270,  430,  438 
solution',  preparation  of,  97 
Albumin  in  urine,  430,  438 

acetic  acid  and  potassium  ferrocyanide 

test  for,  441 

coagulation  or  boiling  test  for,  441 
determination  of,  550 
Heller's  ring  test  for,  439 
Roberts'  ring  test  for,  440 


Albumin  in  urine,  Spiegler's  ring  test  for,  440 

tests  for,  439 
Albumins,  93,  95,  96 
Albuminates.     See  Metaproteins. 
Albuminates,  formation  of,  by  metallic  salts,  101 
Albuminoids,  93,  in,  348 
Albumoscope,  103,  440 
Albumoses  (see  Proteoses,  p.  117) 
Alcaptonuria,  412 
Alcohol,  aldehyde  test  for,  30 

iodoform  test  for,  30 
Alcohol-soluble    proteins  (see  Prolamins,  pp.  93 

and  no 

Alcoholic  urease  solution,  517,  642 
Alcoholic    zinc    chloride    test   for   urobilin,    418 
Aldehyde,  24,  41 
Aldehyde  group,  38 
Aldehyde  test  for  alcohol,  30 
v.  Aldor  s  method  of  detecting  proteose  in  urine, 

443 

Aldose,  19 

Aliphatic  nucleus,  64,  67 

Alizarin  yellow  R,  use  of,  as  indicator,  160,    161 
Alizarin  red  in  acidimetry,  498 
Alkali     albuminate.     See     Alkali     metaprotein. 
Alkali-hematin,  257,  302 
Alkali  metaprotein,  94,  114,  115 
experiments  on,  115 
precipitation  of,  115 
preparation  of,  115 
sulphur  content  of,  115 
Alkalimetry,  496 
Alkaline  tide,  370,  610 

demonstration  of,  610 
"Alkali  reserve,"  determination  of,  319 
Alkali  tolerance,  determination  of,  325 
Alkalosis,  325 
Allantoin,  386,  469 

crystalline  form  of,  409 

experiments  on,  410 

formula  for,  409 

preparation  of,  from  uric  acid,  410 

quantitative  determination  of,  by  Wiechow- 

ski-Handovsky  method,  535 
by  difference,  537 
separation  of,  from  urine,  410 
Alloxyproteic  acid,  386,  409 
Almen's  reagent,  preparation  of,  445.  627 
Aluminium   hydroxide,    use   of,    in    removal    of 

protein,  347,  506,  627 
Alveolar    air,    carbon    dioxide    tension    of,    317 

determination  of,  319 
Amalgamation  test  for  mercury,  465 
Amandin,  93 
Amino  acids,  64,  66,  67,  189,  198,  250,  273,  300, 

386,  411 

preparation  of,  in  crystalline  form,  84,  86 
a-amino-/3-hydroxy-propionic  acid,  68,  72 
oi-amino-/3-imidazol-propionic  acid,  67,  76 
a-amino-iso-butyl-acetic  aCid,  68,  77 
a-amino-normal-glutaric  acid,  68,  81 
Amino-butyric  acid,  217 
Amino  group,  64,  87,  99 
Amino-nitrogen,  qauntitative  determination  of, 

87.  90,  300,  523 
Amino-succinic  acid,  68,  81 
Amino-valeric  acid,  217 
a-amino-iso-valeric  acid,  68,  77 


INDEX 


6S  i 


Ammonia,  63,  66,  70,  106,  250,  273,  387,  420,  519, 

608 

in  blood,  250,  273 
in  urine,  387,  420,  519,  608 

quantitative  determination  of,  519 
Ammoniacal  cupric  hydroxide,  solubility  test,  48 
Ammoniacal  silver  solution,  preparation  of,  627 
Ammoniacal  zinc  chloride  test  for  urobilin,  418 
Ammonium    benzoate,    synthesis    of,    to    form 

hippuric  acid,  619 
Ammonium     magnesium     phosphate     ("Triple 

phosphate").  380,  426 
crystalline  form  of,  426 
in  urinary  sediments,  475 
Ammonium  purpurate,  127,  397 
Ammonium  urate,  380,  394,  478,  532 

crystalline  form  of,  Plate  VI,  opposite 

P-  479 

Amphopeptone,  95,  118 
Amygdalin,  4 
Amylase,  pancreatic,  4,  u,  190,  194,  300 

digestion  of  dry  starch  by,  191,  195 

inulin  by,  195 
experiments  on,  n,  194 
influence  of  bile  upon  action  of,  195 
most  favorable  temperature  for  action 

of,  195 
salivary,  4,  10,  54,  139 

activity  of,  in  stomach,  56,  139 
experiments  on,  10,  58 
inhibition  of  activity  of,  56,  60 
nature  of  action  of,  55,  60 
products  of  action  of,  55,  59 
vegetable,  4,  n 
Amylases,  4,  10,  54,  190 

experiments  on,  10,  58,  194,  242 
Amylocellulose,  42 
Amyloid,  48,  112 
Amylolytic  enzymes.     See  Amylases. 

quantitative  determination  of  activity 

of,  195,  242,  300 
Amylopectin,  42 
Amylose,  42 
Anabolism,  579 
Animal  parasites  in  feces,  230 

in  urinary  sediments,  482,  491 
Anti-enzymes,  9 

experiments  on,  17 

Antimony  pentachloride  as  cellulose  solvent,  49 
Antimony  trichloride  as  cellulose  solvent,  48 
Antipepsin,  9,  17 
Antipeptone,  95,  118 
Antirennin,  9 
Antithrombin,  260 
Antitrypsin,  9,  18 
Aporrhegmas,  217 
Arabinose,  19,  36,  458 

Dial's  reaction  for,  37,  458 
orcinol  test  on,  37,  458 
phenylhydrazine  test  on,  37 
Tollens'  reaction  on,  37,  458 
Arginase,  4 

Arginine,  4,  67,  68,  79,  190 

Arnold-Lipliawsky  reagent,  preparation  of,  627 
Aromatic  oxyacids,  386,  411 
Arsenic  in  urine,  detection  of,  462 

determination  of,  462 
Arthritis,  blood  in,  273 


Ascaris,  17,  1 8 

Ash  of  milk,  quantitative  determination  of,  345 

Asparagine,  81 

formula  for,  81 
Aspartic  acid,  64,  66,  67,  80,  81 

crystalline  form  of,  80 

formula  for,  81 
Assimilation  limit,  21 

Assimilation  limit  of  dextrose,  21,  431,  60 1 
Atomic  weights,  table  of,  644 
Autolytic  enzymes,  3 

Automatic  regulation  of  gastric  acidity,  149 
Azolitmin,  use  of,  as  indicator,  161 

Babcock  fat  method,  342 

tube,  342 
Bacteria  in  feces,  224,  227,  228,  244,  621 

'     quantitative  determination  of,  244 
Bacterial  nitrogen  in  feces,  229,  621 
determination  of,  244 
Balance,  metabolic,  preparation  of,  625 
calcium,  625 
magnesium,  625 
nitrogen,  625 
phosphorus,  625 
sulphur,  625 

Bang  reduction  flask,  289 
Bang's  method  for  estimation  of  sugar  in  blood, 

288 
Bang's  method  for  estimation  of  sugar  in  urine, 

542 

Barfoed's  reagent,  preparation  of,  29,  203.  628 
Barfoed's  test  for  monosaccharides,  29 
Baryta  mixture,  preparation  of,  392,  628 
Basal  metabolism,  328 
Base-forming  foods,  influence  of  on  hydrogen  ion 

concentration  of  urine,  379,  613 
Ba'feic  lead  acetate  solution,  558,  629 
Bayberry  tallow,  saponification  of,  184 

source  of,  184 

Bayberry  wax.     See  Bayberry  tallow,  1.84 
Bead  test  (Einhorn),  241 
Beckmann-Heidenhain  apparatus,  382 
"  Bence- Jones'  protein,"  detection  of,  444 

quantitative  determination  of,  552 
Benedict  creatine  preparation,  401 
Benedict   and    Bock's   method   for   quantitative 

determination  of  total  nitrogen,  512 
Benedict-Folin  creatinine  preparation,  400 
Benedict-Folin  method  for  creatine  in  urine,  529 
Benedict-Murlin  method  for  amino-acid  nitrogen 

in  urine,  525 

Benedict's     method     for     quantitative     deter- 
mination of  sugar,  538 

Benedict's  micro-method  for  quantitative  deter- 
mination of  sugar,  539 

Benedict's  method  for  sugar  in  normal  urine,  549 
Benedict's     method     for      quantitative     deter- 
mination of  sulphur,  565 
Benedict's  modification  of  Benedict    and  Lewis 

method  for  sugar  in    blood,  287 
Benedict's  solution,   for  use  in  quantitative  deter- 
mination of  sugar,  preparation  of,  538,  629 
sulphur  reagent,   preparation   of,     565,    630 
Benzidine    peroxidase    reaction   (Wilkinson  and 

Peters),  338 

Benzidine  reaction  for  blood,  174,  236,  266,  445 
Benzoic  acid,  71,  386,  405,  412,  616,  619 


INDEX 


Benzole  acid,  crystalline  form  of,  413 
experiments  upon,  413 
formula  for,  412 
solubility  of,  413 
sublimation  of,  413 
Bergeim,   Halverson,   method  for  determination 

of  calcium  in  blood,  293 
Bergeim's    intragastric    conductance    apparatus, 

152 
Bergeim's     modification    of    the     Herter-Foster 

method  for  indole  in  feces,  245 
Bergeim's  phosphonuclease  theory  for  the  origin 

of  hydrochloric  acid  of  gastric  juice,  140 
Berthelot- At  water  bomb  calorimeter,  617 
Bertrand's  method  for  sugar  determination,  545 
Bial's  reaction  for  pentoses,  37,  458 
Bial's    reagent,    preparation     of,    37,    458,    630 
Bicarbonate  of  plasma,  titration,  318 
Bile,  174,  205,  430,  448 
analysis  of,  206 
constituents  of,  206 
daily  secretion  of,  206 
freezing-point  of,  206 
influence  on  digestion,  gastric,  146 

pancreatic,  194,  196 
inorganic  constituents  of,  206,  210 
nucleoprotein  of,  206,  210 
reaction  of,  205,  210 
secretion  of,  205 
specific  gravity  of,  206 
Bile  acids,  207,  211 

Hay's  test 'for,  212 
Mylius's  test  for,  211 
Neukomm's  test  for,  212 
Oliver's  test  for,  212 
Pettenkof er's  test  for,  211 
tests  for,  211 

v.  Udransky's  test  for,  211 
Bile  acids  in  feces,  detection  of,  239 
Bile  acids  in  urine,  430,  449 

Hay's  test  for,  449 
Mylius's  test  for,  449 
Neukomm's  test  for,  450 
Oliver's  test  for,  450 
Pettenkofer's  test  for,  449 
tests  for,  449 

v.  Udransky's  test  for,  449 
Bile  pigments,  206,  207,  210 

Gmelin's  test  for,  210 
Huppert-Cole  test,  210 
Rosenbach's  test  for,  eio 
tests  for,  210       v' 
Bile  pigments  in  urine,  430,  448 

Gmelin's  test  for,  448 
Huppert-Cole  test  for,  448 
Rosenbach's  test  for,  448 
tests  for,  448 
Bile  salts,  207,  449 

crystallization  of,  207,  212 
Biliary  calculi,  209,  212 
analysis  of,  212 
Bilicyanin,  207 
Bilifuscin,  207 
Bilihumin,  207 
Biliprasin,  207    . 
Bilirubin,  207 

crystalline  form  of,  208 

in  urinary  sediments,  475,  481 


Biliverdin,  207,  209 

"Biological"  blood  test,  260 

Bismuth,  influence  on  color  of  feces,  225,  241 

Bismuth  reduction  tests,  28,  436 

Bismuth  test  for  choline,  375 

Biuret,  99,  390,  392 

formation  of,  from  urea,  99,  390 
Biuret  paper  of  Kantor  and  Gies,  100 
Biuret  potassium  cupric  hydroxide..    See  Cupri- 
potassium  biuret,  99 
test,  99 

Posner's  modification  of,  100 
Biuret  reagent  (Gies),  preparation  of,  100 
Black's  reaction  for  /3-hydroxybutyric  acid,  455 

reagent,  preparation  of,  455,  631 
Blood,  173,  228,  236,  248,  273,  430,  445 
acetoacetic  acid  in,  250,  273,  327 
acetone  in,  250,  273,  327 
agglutination  of,  253,  265 
amino-acid  nitrogen  in,  273,  300 
amino-acids  in,  250,  251 
ammonia  in,  273 
analysis,  273 

benzidine  test  for,  174,  236,  266,  445 
Bordet  test  for,  260 
calcium  in,  273,  293 
cholesterol  in,  250,  273,  291 
coagulation  of,  260 

Howell's  theory  of,  260 

composition  of  normal  and  pathological,  273 
constituents  of,  250,  251 
creatine  in,  251,  273,  281 
creafinine  in,  251,  273,  280,  281 
crystallization  of  oxyhemoglobin  of,  253,  269 
defibrinated,  260,  263 
detection  of,  173,  236,  266,  271,  445 
determination  of  acetone  in,  327 
acetoacetic  acid  in,  327 
amino-acid  nitrogen  in,  300 
calcium  in,  273,  293 
chlorides  in,  285 
cholesterol  in,  291,  293 
creatine  in,  281 
creatinine  in,  280 
fat  in,  273,  299 
^3-hydroxybutyric  acid  in,  327 
hydrogen  ion  concentration  in,  326 
non-protein  nitrogen  in,  277 
sugar  in,  273,  283,  287,  288 
total  nitrogen  in,  273 
total  solids  in,  273 
urea  in,  273,  278,  279,  286 
uric  acid  in,  273,  281 
drawing  of,  for  analysis,  275 
erythrocytes  of,  252,  264,  489 
experiments  on,  263,  273 
fat  in,  250,  299 
form  elements  of,  252 
Gregersen  and  Boas  variation  of  benzidine 

test,  267 

guaiac  test  for,  236,  238,  261,  265,  446 
hemin  test  for,  267,  446 
/3-hydroxybutyric  acid  in,  273 
in  arthritis,  273,  275 
in  cholelithiasis,  250,  273,  275 
in  diabetes,  273,  274 
in  gout,  251,  273,  274,  396 
in  lipemia,  273,  275 


INDEX 


6S3 


Blood  in  nephritis,  273,  274 
in  uremia,  273,  274 
in  urine,  430,  445 
leucocytes  of,  258 
medico-legal  tests  for,  260,  267 
menstrual,  260 
microscopical     examination     of,     252,     263, 

271 
non-protein  nitrogen  of,  273 

determination  of,  277 
nucleoprotein  of,  249,  250 
"occult,"  in  feces,  228,  236 
ortho-tolidin  test  for,  173,  237,  266,  446 
oxyhemoglobin  of,  253,  300 
pigment  of,  253,  257 
plaques,  259 
plasma,  248,  271 
platelets;  259 
plates,  259 

preparation  of  hematin  from,  269 
preparation  of  "laky,"  248,.  264 
preservation  of,  for  analysis,  2-77 
reaction  of,  248,  263 
serum,  250,  270 
specific  gravity  of,  248,  263 
spectroscopic  examination  of,  300 
stains,  271 

sugar  in,  250,  271,  273,  283,  287,  288 
test  for  iron  in,  264 
total  amount  of,  248 
Blood  analysis,  273 
Blood  casts  in  urine,  482,  486 
Blood  corpuscles,  252,  258,  264,  482,  489  ' 
Blood  dust,  248,  259 
Blood  in  urine,  430,  445 

benzidine  reaction  for,  445 
guaiac  test  for,  446 
Heller's  test  for,  446 
Heller-Teichmann  reaction  for,  446 
ortho-tolidin  test  for,  446 
spectroscopic  examination  of,  447 
Teichmann's  hemin  test  for,  446 
tests  for,  445 
Blood  plasma,  248,  271 

constituents  of,  248 
effect  of  calcium  on  oxalated,  271 
experiments  on,  271 
preparation  of  fibrinogen  from,  271 
oxalated,  271 
salted,  271 
Blood  serum,  250,  270 

coagulation  temperature  of,  270 
constituents  of,  250,  270 
experiments  on,  270 
precipitation  of  proteins  of,  270 
separation  of  albumin  and  globulin  of, 

270 

sodium  chloride  in,  270 
sugar  in,  270 

Blood  stains,  examination  of,  271 
Bloor's  nephelometer,  cut  of,  295 

method  for  determining  cholesterol  in  blood, 

293 

method  for  determining  fat  in  blood,    299 
Boas'  reagent,  as  indicator,  158 

preparation  of,  158,  631 
Bock  and  Benedict's  apparatus,  cut  of,  512 
Bock  and  Benedict's  colorimeter,  509 


Bock  and   Benedict's   microchemical  method  for 

total  nitrogen  in  urine,  512     * 
"Bolting"  of  food,  influence  of,  on  food  residues 

in  feces,  623 

Bomb  calorimeter,  Berthelot-Atwater,  617 
Bone,  constituents  of,  354-356 
ossein  of,  preparation  of,  354 
quantitative  composition  of,  354,  355 
Bone  ash,  scheme  for  analysis  of,  356 
Borchardt's  reaction  for  fructose,  35,  461 
Bordet  test,  detection  of  human  blood  by,  256 
Boric  acid  and  borates  in  milk,  detection  of,  340 
Bromelin,  5 

Bromine  test  for  melanin,  466 
for  tryptophane,  192 
Buccal  glands,  53 

"Buffer  substances"  of  the  blood,  309,  310 
Buffy  coat,  formation  of,  250 
Bunge's  mass  action  theory,  139 
Burge   apparatus  for  quantitative  determination 

of  catalase,  17 
Butter,  composition  of,  336 
Butyric  acid,  8,  336,  340,  387,  415 
Butyrin,  180,  329,  336 
Bynin,  93,  rto 

Cadaverine,  80,  215 
Calcium  in  urine,  387,  427,  475-7,  574 
in  blood,  273 

in  blood  determination  of,  293 
quantitative  determination  of,  574 
balance,  preparation  of,  625 
carbonate  in  urinary  sediments,  475,  476 
caseinate,  336 

in  bone,  detection  of,  354-6 
in  feces,  estimation  of,  625 
oxalate,  408,  475 

in  urinary  sediments,  475 
paracasein,  142,  333 

phosphate  in  urinary  sediments,  475,  477 
in  bone,  detection  of,  355-6 
in  milk,  331,  340 

sulphate  in  urinary  sediments,  475,  477 
Calcium-pigment  calculi  in  bile,  210 
Calculi,  biliary,  209,  212 

Cholesterol-calcium,  210 
Cholesterol-calcium-pigment,  210 
Calcium-pigment,  210 
urinary,  492 

calcium  carbonate  in,  493 
cholesterol  in,  495 
cystine  in,  493,  495 
fibrin  in,  495 
indigo  in,  495 
oxalate  in,  493 
phosphates  in,  493 
uric  acid  and  urates  in,  493 
urostealiths  in,  495 
xanthine  in,  493 
Calliphora,     larvae    of,    formation    of    fat    from 

protein  by,  179 

Calomel,  influence  on  color  of  stool,  225,  241 
Cambogia,    influence  of,   on  color  of  feces,   241 
Camphor  as  urine  preservative,  385 
Cane  sugar  (see  Sucrose,  p.  40) 
Canton  silk,  68 
Caproic  acid,  329,  336 
Carbamic  acid,  250 


654 


INDEX 


Carbocyclic  nucleus,  64,  67,  68 
Carbohydrases,  4 
Carbohydrate  tolerance  test,  290 
Carbohydrates,  19 

absorption  of,  as  influenced  by  fat  ingestion, 
602 

classification  of,  19 

composition  of,  19 

control  of  putrefaction  by,  216 

in  feces,  estimation  of,  624 

protein-sparing  action  of,  612 

review  of,  50 

scheme  for  detection  of,  52 

variation  in  solubility  of,  20 
Carbonates  in  urine,  387,  428 
Carbon  dioxide  of  expired  air,  demonstration,  328 
capacity  of  plasma,  311 
tension  of  alveolar  air,  319    . 
Carbon  moiety  of  protein  molecule,  182 
Carbon  monoxide,  hemoglobin,  257,  301 

spectroscopic  test  for,  301  , 

tannin  test  for,  302 
Carboxylase,  4,  10,  31,  438 
Carmine-fibrin,  preparation  of,  12,  631 
Carmine,  use  in  feces  separation,  238,  620 
Carnine,  358 
Carnitine,  358 

formula  for,  364 
Carnomuscarine,  358 
Carnosine,  358,  364 
Carotin,  336 
Cartilage,  353 

constituents  of,  353 

experiments  on,  353 

Hopkins-Cole  reaction  on,  353 

Millon's  reaction  on,  353 

preparation  of  gelatin  from,  353 

solubility  of,  353 

unoxidized  sulphur  in,  353 

xanthoproteic  test  on,  353 
Casein,  66,  142,  329,  33i,  336,  339 

action  of  rennin  upon,  142,  331 

biuret  test  on,  339 

decomposition  of,  66 

Millon's  test  on,  339 

precipitation  of,  339 

preparation  of,  339 

quantitative  determination  of,  346-7 

quantitative  determination  of,  Hart's  method 
for,  346 

solubility  of,  339 

soluble,  142 

test  for  phosphorus  in,  339 

test  for  unoxidized  sulphur  in,  339 
Caseinate,  calcium,  336 
Caseinogen.     See  Casein. 
Casts,  484-9 

blood,  484,  487 

epithelial,  484,  487 

fatty,  484,  487 

granular,  484,  487 

hyaline,  484,  487 

pus,  484,  489 

waxy,  484,  488 

Casts  in  urinary  sediments,  484—9 
Catabolism,  579 
Catalase,  5,  15 

animal,  16 


Catalase,  experiments  on,  16 

quantitative  determination  of,  16 

vegetable,  16 
Catalysis,  2 
Cat  gut,  146 
Cell,  580 
Cellulose,  20,  47 

action  of  Schweitzer's  reagent  on,  48 

hydrolysis  of,  48 

iodine  test  on,  48 

solubility  of,  48 

solvents,  48 

utilization  by  animals,  47 
Cellulose  group,  20 
Cerebrin  (cerebroside) ,  370,  372,  374 

experiments  on,  374 

hydrolysis  of,  374 

microscopical  examination  of,  374 

preparation  of,  374 

solubility  of,  374 
Cerebrosides,  370,  372 
Cerebro-spinal  fluid,  choline  in,  371 
Charcot-Leyden  crystals,  228 

form  of,  228 
Chlorides  in  blood,  273,  285 

quantitative  determination  of,  285 

in  urine,  387,  423,  572 
detection  of,  424 

quantitative  determination  of,  572 
Cholecyanin,  209 
Cholelithiasis,  blood  in,  273,  292 
Choleprasin,  208 

Cholera-red  reaction  for  indole,  221 
Cholesterol,  206,  213,  250,  273,  291,  329,  370,  372 

crystalline  form  of,  213 

formula  for,  372 

in  blood,  250,  273,  274,  291 
determination  of,  291 

iodine-sulphuric  acid  test  for,  213,  374 

isolation  of,  from  biliary  calculi,  212 

Liebermann-Burchard  test  for,  213,  374 

occurrence  of,  in  urinary  sediments,  475,     80, 
495 

origin  of,  372 

preparation  of,  from  nervous  tissue,  373 

Salkowski's  test  for,  213,  374 

Schiff's  reaction  for,  213,  374 

tests  for,  213,  374 
Cholesterol-calcium  calculi,  210 
Cholesterol-calcium-pigment  calculi,  210 
Choletelin,  208 
Choline,  215,  371,  374 

as  putrefaction  product,  215 

formula  for,  371 

tests  for,  374 
Chondrigen,  112 
Chondroalbumoid,  353 
Chondroitin,  353 

Chondroitin-sulphuric  acid,  353,  387,  410 
Chondromucoid,  112,  353 
Chondrosin,  353 

reducing  action  of,  353 
Chromoproteins  (see  Hemoglobins),  112 
Chyle,  263 

Cleavage    products    of   protein    (see    Decompo- 
sition products),  63,  67-68 
Clupeine,  66,  94 
Coagulases,  4 


INDEX 


655 


Coagulated  proteins,  95,  "5 
biuret  test  on,  117 
digestion  of,  117 
formation  of,  116 
Hopkins-Cole  reaction  on,  117 
Millon's  reaction  on,  117 
solubility  of,  117 
xanthoproteic  reaction  on,  117 
Coagulation  of  blood,  259 

Howell's  theory  of,  260 
Coagulation  of  proteins,  115 

changes  in  composition  during,  116 
fractional,  104,  116 

Coagulation  temperature  of  proteins,  104,  116 
apparatus  used  in  determining,  105 
method  employed  in  determining,  104 
Cochineal,  use  of,  160,  161 

indicator  for  total  phosphates  in  urine,  569 
Co-enzyme,  7 

Collagen,  93,  in,  349.  3SO 
experiments  on,  350 
percentage  of,  in  ligament,  352 

in  tendon,  349 

production  of  gelatin  from,  350,  351 
solubility  of,  351 
transformation  of,  350,  351 

Collection  and  preservation  of  feces  in  metabo- 
lism experiments,  621 
of  urine  in  metabolism  experiments,  384, 

598 

Collodion  dialyzer,  24 
Colloidal  solution,  330 
Colloids,  330,  358 

tissue,  358 
Colostrum,  331,  333,  386 

microscopical  appearance  of,  331 
Combined  hydrochloric  acid  (protein  salt),  55 

139.  176,  178,  631 
preparation  of,  631 
tests  for,  178 

Combustion  of  foodstuffs,  618 
Composition  of  ccmmon  foods  (Table),  602 
Compound  test  for  lactose  in  urine,  460 
Congealing-point  of  fat,  187 
Congo  red,  as  indicator,  156,  157 

preparation  of,  632 

Congo-red  fibrin,  preparation  of,  12,  632 
Conjugated  proteins,  94,  in 
classes  of,  94,  in 
nomenclature  of,  94,  in 
occurrence  of,  94,  in 
Conjugate  glycuronates,  26,  434,  456 

naphthoresorcinol  reaction  for,  456 
polariscopic-fermentation  test  for,  456 
reduction-polariscopic  test  for,  457 
Connective  tissue,  349 
Constipation,  aid  in,  50,  226 
Copper  soap  test  for  lipase,  197 
Copper   sulphate   solution,    Folin-McEllroy,    for 

sugar  in  urine,  27,  435,  633 
Cowie's  guaiac  test,  238 
Cfeatine,  250,  251,  273,  281,  360,  363,  367,  386 

401,  430,  529 
crystalline  form  of,  360 
diacetyl  reaction  for,  368 
formula  for,  363 

quantitative  determination  of,  281,  529 
separation  of,  from  meat  extract,  367 


Creatine,  transformation  into  creatinine,  368 
Creatinine,  26,  251,  273,  387,  308 

coefficient,  definition  of,  398,  528 

crystalline  form  of,  399 

daily  excretion  of,  399 

elimination,  a  study  of,  607 

experiments  on\40O 

formula  for,  398 

from  creatine,  368 

Jaffe's  reaction  for,  402 

quantitative  determination  of,  281,  529 

Salkowski's  test  for,  402 

separation  of,  from  urine,  400 

Weyl's  test  for,  402 

Creatinine-zinc   chloride,   formation  of,  400,  402 
Cresol,  para,  215 

tests  for,  222 
Croll's  fat  apparatus,  343 
Cross  and  Sevan's  reagent,  48 
preparation  of,  48 
solubility  test,  48 
Cryoscopy    382 
Cul-de-sac,  138 
Cupri-potassium  biuret,  formation  of,  99 

formula  for,  99 
Cyanuric  acid,  390 

formula  for,  390 

Cylindroids  in  urinary  sediments,  482,  489 
a-Cyprinine,  66 
Cystine,  64,  66,  68,  74,  86,  475,  479 

crystalline  form  of,  75,  479 

detection  of,  86,  479 

formula  for,  75 

in  hair,  86 

in  urinary  sediments,  475,  479 

preparation  of,  in  crystalline  form,  86 
Cytosine,  124,  125,  127,  132 

Wheeler- Johnson  reaction  for,  132 

Deaminases,  4 

Decomposition  products  of  proteins,  63,  66,  67, 

68,  70 

crystalline  forms  of,  71-83 
experiments  on,  84-86 
isolation  of,  84-86 
Defensive  enzymes,  3 
Deficiencies  of  diet,  580 

Degradation  products  of  protein  (see  Decomposi- 
tion products),  63,  66-68,  70 
Delusive  feeding  experiments,  137 
Derived  proteins,  93,  113 
Detection  of  preservatives  in  milk,  340- 
boric  acid  and  borates,  341 
formaldehyde,  340 
hydrogen  peroxide,  341 
salicylic  acid  and  salicylates,  341 
Determination  of  acetoacetic  acid  in  blood,  327 

in  urine,  552 
acetone  in  blood,  327 
in  urine,  552,  557 
and  diacetic  in  blood,  327 
in  urine,  552 

acetone  bodies  in  urine,  552 
acidity  of  urine,  by  titration,  499 

by  hydrogen  ion  concentration,  500 
albumin  in  urine,  550 
"alkali  reserve"  of  the  blood,  311-325 
alkali  tolerance,  325 


656 


INDEX 


Determination  of  allantoin  in  urine,  535 
alveolar  carbon  dioxide,  319,  321 
amino  acid  nitrogen,  87,  90,  300,  523 
in  blood,  300 

in  protein  hydrolysis,  63,  87,  90 
in  urine,  523 
ammonia  in  urine,  519 
amylolytic  activity,  195,  242 
ash  of  milk,  345 
basal  metabolic  rate,  328 
bicarbonate  of  plasma,  318 
calcium  in  blood,  293 
calcium  in  urine,  574 
carbohydrate  tolerance,  290 
carbon  dioxide  tension  of  alveolar  air,  319,  321 
casein  of  milk,  346 
catalase,  16 
chlorides  in  blood,  285 

in  urine,  572 
cholesterol  in  blood,  291 
creatine  in  blood,  281 

in  urine,  529 
creatinine  in  blood,  280 

in  urine,  526 

diacetic  acid  (see  Acetoacetic  acid), 
fat  in  blood,  299 
„  in  f eces,  246 
in  milk,  342 
fecal  amylase,  242 
fecal  bacteria,  244 
glucose  in  urine,  538-549 
hemoglobin  of  blood,  327 
hippuric  acid  in  urine,  537 
hydrogen  ion  concentration  of  blood,  326 

of  urine,  500 

0-hydroxy butyric  acid  in  urine,  557        , 
index  of  acid  excretion  in  urine,  324 
indican  in  urine,  558 
indol  in  feces,  246 
iron  in  urine,  577 
kidney  efficiency,  470 
lactalbumin  in  milk,  346 
lactose  in  milk,  346 
magnesium  in  urine,  514 
nitrogen  in  urine,  504 
non-protein,  in  blood,  277  j  - 

partition  in  urine,  505,  610 
oxalic  acid  in  urine,  562 

/3-oxybutyric  acid  (see  0-hydroxy  butyric  acid) 
oxygen  of  blood,  327 
peptic  activity,  168 
phenols  in  urine,  559 
phosphorus  in  urine,  568 
potassium  in  urine, -5  76 
protein  in  milk,  345,  346 

in  urine,  550 

purine  bases  in  urine,  533 
purine  nitrogen  in  urine,  535 
respiratory  exchange,  328 
sodium  in  urine,  576 
sugar  in  blood,  283,  287 

in  urine,  538-549 
sulphur  in  urine,  562 
total  solids  in  milk,  344 

in  urine,  504 
tryptic  activity,  171 
urea  in  blood,  278,  286 
in  urine,  514 


Determination  of  uric  acid  in  blood,  281 

in  urine,  530 
Deuteroproteose,  94,  118 
Dextrin,  20,  42,  46,  55 
achroo-,  42,  55 

a-achroo-,  55 

/8-achroo-,  55 

•y-achroo-,  55 

action  of  tannic  acid  on,  47 

diffusibility  of,  47 

erythro-,  42,  55 

Fehling's  test  on,  47 

hydrolysis  of,  47 

in  presence  of  starch,  detection  of,  47,  52 

iodine  test  on,  46,  52 

solubility  of,  46 
Dextrosazone,    crystalline    form    of,    Plate    III, 

opposite  p.  22 
Dextrose  (see  Glucose). 
Diabetes,  blood  in,  273 
Diacetic  acid  (see  Acetoacetic  acid). 
Dialysis,  24 

Dialyzers,  preparation  of,  24 
Diamino  acid  nitrogen,  63 
Diaminotrihydroxydodecanoic  acid,  84 
a-e-di-amino-caproic  acid,  67,  79 
Diastase  (see  Vegetable  amylase),  4,  10 
Diazo-benzene-sulphonic  acid,  469 

reagent,  preparation  of,  469 
Diazo  reaction  (Ehrlich's),  469 
Diet,  adequate,  580 

amino  acid  deficiency  in,  589 

calcium  deficiency  in,  596 

carbohydrate  deficiency  in,  594 

deficiencies,  580 

energy  deficiency  in,  596 

fat  deficiency  in,  595 

protein  deficiency  in,  589 

vitamine  deficiency  in,  581-585 

water  deficiency  in,  597 
Differentiation  between  pepsin  and  pepsinogen, 

140,  145 
Digestion,  gastric,  137 

intestinal,  198 

pancreatic,  187 

salivary,  53 

Di-iodo-hydroxypropane  (lothion),  29,  437 
Di-methyl-amino-azobenzene     (see    Topfer's    re- 
agent), 177 

2,  s-dinitrohydroquinol  use  of,  161 
Dipeptides,  65,  95 
Disaccharides,  19,  37 

classification  of,  19 

Dissociation   products    of    protein    (see    Decom- 
position products),  63 
Donne's  pus  test,  448 

Drying  method  for  determination  of  total  solids 
in  urine,  504 

Earthy  phosphates  in  urine,  424,  426,  569 
quantitative  determination  of,  569 
Edestan,  94,  113 

experiments  on,  114 
Edestin,  66,  93,  108 

coagulation  of,  108 

crystalline  forms  of,  108 

decomposition  of,  66 

microscopical  examination  of,  108 


INDEX 


6S7 


Edestin,  Millon's  test  on,  108 

preparation  of,  108 

solubility  of,  108 

tests  on  crystallized,  108 

filtrate  of,  109 
Ehrlich's  diazo-benzene-sulphonic    acid    reagent, 

preparation  of,  469 
Ehrlich's  diazo  reaction,  469 
Einhorn's  bead  test,  241 
Einhorn's  saccharometer,  30 
Elastin,  93,  349,  3SL  352 

absorption  of  pepsin  by,  352 

experiments  on,  352 

preparation  of,  352 

solubility  of,  352 

Electrical  conductivity  of  urine,  383 
Electrolytes,    influence   on   enzyme   activity,    7, 

191 

Embryos,  glycogen  in,  359 
Emulsin,  4 

Energy  metabolism,  579,  596,  618 
Enterokinase,  190,  199,  200 

demonstration  of,  200 
Enzymes,  i 

activation  of,  6 

adsorption  of,  6 

classification  of,  4 

defensive,  3 

definition  of,  2 

experiments  on,  10 

influence  of  electrolytes,  7,  191 

list  of,  4 

preparation  of,  5,  n,  13,  14 

properties  of,  6 

reference  books,  10 
Epiguanine,  386,  419 
Episarkine,  386,  419 
Epithelial  cells  in  urinary  sediments,  482 

casts  in  urinary  sediments,  482,  486 
Epithelial  tissue,  348 

experiments  on,  349 
Erepsin,  5,  198,  201 

experiments  on,  201 
Erythrocytes,  252,  264,  489,  490 

crenated,  490 

diameter  of,  252 

form  of,  252 

Erythrocytes,  influence  of  osmotic  pressure  on, 
264 

in  urinary  sediments,  482,  489 

number  of,  per  cubic  millimeter,  252,  253 

of  different  species,  252 

stroma  of,  252 

variation  in  number  of,  253 
Erythro-dextrin,  42,  55 
Esbach's  albuminometer,  551 

method  for  determination  of  albumin,  551 

reagent,  preparation  of,  551 
Ester,  definition  of,  179 

hydrochloric  acid,  of  hematin,  269 

sulphuric  acid,  of  hematin,  269 
Ethereal  sulphates,  386,  402 

quantitative  determination  of,  564,  567 
Ethereal  sulphuric  acid,  215,  386,  402 
Ethyl  butyrate  test  for  pancreatic  lipase,  197 

sulphide,  409 
Euglobulin,  249 
Excelsin,  109 
42 


Excelsin,  crystalline  form  of,  109 
Extractives  of  muscular  tissue,  358 

nitrogenous,  358 

non-nitrogenous,  358 

Farmer-Folin  microchemical  method  for  nitrogen 

in  urine,  508 
Fasting,  feces  in,  230 

metabolism  in,  618 
Fatigue  substances  of  muscle,  363 
Fats,  179 

absorption  of,  181,  191 

apparatus     for     determination     of  melting- 
point  of,  1 86 

chemical  composition  of,  179,  180 

congealing-point  of,  187 

crystallization  of,  181,  184 

digestion  of,  181,  191 

emulsification  of,  181,  183 

experiments  on,  183 

formation  of,  from  protein,  182 

formation  of  acrolein  from,  183 

hydrogenation  of,  180 

hydrolysis  of,  180 

influence  of.jpn  carbohydrate  absorption,  599 

in  milk,  329,  333,  336,  340,  341 

in  urine,  430,  459,  486 

melting-point  of,  181,  186 

nomenclature  of,  179,  180 

occurrence  of,  179 

permanent  emulsions  of,  181,  183 

protein-sparing,  action  of,  612 

quantitative  determination  of,  in  milk,  342 

rancid,  181 

reaction  of,  181 

saponification  of,  180,  184,  185 

solubility  of,  181,  183 

transitory  emulsions  of,  181,  183 
Fat-soluble  "A,"  influence  of  on  growth,  581,  585 

occurrence  of.  581 
Fat-splitting  enzymes    (see  Lipases,   5,    13,    181, 

191,  196) 

Fatty  acid,  179,  181,  185,  215,  387,  415 
Fatty  casts  in  urinary  sediments,  486,  488 
Fatty  degeneration,  182 
Fecal  amylase,  quantitative  determination  of, 

242 
Fecal  bacteria,  224,  227,  229,  244,  621 

quantitative  determination  of,  244 
Feces,  224,  620,  625 

agar-agar,  influence  of,  227,  618,  622 

albumin  and  globulin  in,  240 

bacteria  in,  224,  227,  229,  244,  621 

bacterial  nitrogen  in,  demonstration  of,  621 

bile  acids  in,  239 

bilirubin  in,  225,  239 

blood  in,  228,  236 

carbohydrate  in,  estimation  of,  624 

casein,  239 

cholesterol  in,  227,  235 

collection  and  preservation  in  metabolism 
experiments,     621 

color  of,  influence  of  drugs  and  foods  upon 
241 

daily  excretion  of,  224,  621 

enzymes  of,  229,  242 

experiments  on,  232,  620,  625 

"fasting,"  230 


658 


INDEX 


Feces,  fat  in,  determination  of,  246 
food  residues  in,  230,  623 
form  and  consistency  of,  226 
hydrobilirubin  in,  225,  238 
hydrogen  ion  concentration  of,  226 
indole  in,  226,  240 

determination  of,  245 

influence  of  defective  mastication  on,  623 
inorganic  constituents  of,  228,  240,  624 

elements  of,  demonstration  of,  624 
Lyle  Curtman  procedure,  228,  236 
macroscopic  constituents  of,  227,  232 
metabolic  product,  nitrogen  in,  230,  622 
microscopic  constituents  of,  227 
microscopical  examination  of,  232 
nitrogen  of,  230,  622 
nucleoprotein  in,  239 
odor  of,  226 

parasites  and  ova  in,  230 
pigment  of,  225 
proteose  and  peptone  in,  240 
reaction  of,  226 
Scybala  form  of,  226 

separation  of,  importance  of,  227,  242,  620 
separation  of,  experiment  on,  242,  620 
weighing  of,  621 
Fehling's   method  for  determination  of  glucose 

in  urine,  541 

Benedict's    modification    of,    538 
solution,  preparation  of,  632 
test,  25,  433 

Benedict's  modification  of,  26,  435 
Fermentation,  lactic  acid,  172,  331 

"sugar-free,"  10,  31,  438 

Fermentation  method  for  determination  of  glu- 
cose, 548 

Fermentation  test,  30,  438 
Ferments,  classification  of,  4 
Ferric  chloride  test  for  acetoacetic  acid,  454 
for  thiocyanate  in  saliva,  58 
for  melanin  in  urine,  466 
Feser's  lactoscope,  344 
Fibrin,  249,  259,  271,  486,  491 
carmine,  preparation  of,  12' 
congo-red,  preparation  of,  12 
in  urinary  sediments,  486,  491 
separation  of,  from  blood,  250,  259 
solubility  of,  271 
Fibrin  ferment,  250,  259 
Fibrin-heteroproteose,  67 
Fibrinogen,  250,  259,  260,  271 
Fibroin,  Tussah  silk,  67 
Fischer  apparatus,  74 

photograph  of,  74 
Fluorides  in  urine,  387,  429 
Fly-maggots,  experiments  on,  182 
Foam  test  for  bile  acids,  211,  449 
Folin  apparatus  for  nitrogen,  etc.,  511 
Folin  fume  absorber,  505 
Folin's    method    for    determination    of    acetone 

in  urine,  557 

'    acidity  of  urine,  by  titration,  499 
ammonia,  519 

creatinine  in  urine,  526,  528 
ethereal  sulphates,  564 
inorganic  sulphates,  564 
total  sulphates,  562 
of  preparing  cystine,  86 


Folin's   sugar  reagent,  test  for  sugar  in  normal 

urine,  414 

test  for  uric  acid,  398 
theory  of  protein  metabolism,  612 
Folin   and    Bell's   method   for  determination  of 

ammonia  in  urine,  522 
Folin  and  Denis'  direct  nesslerization  method  for 

nitrogen  in  urine,  513 
Folin  and  Denis'  method  for  phenols  in  urine,  559 

Tisdall's  modification  of,  561 

Folin  and  Denis'  method  for  Bence- Jones  pro- 
tein, 552 
Folin    and    Denis*    nephelometric    method    for 

albumin  in  urine,  551 
Folin  and  Flanders'  method  for  hippuric  acid  in 

urine,  537 
Folin  and  Youngburg  direct  nesslerization  method 

for  ammonia  in  urine,  517 
Folin- McEllroy  test  for  sugar,  27,  435 
Folin- McEllroy  reagent,  27,  435,  633 
Folin- McEllroy-Peck  method  for  determination 

of  sugar  in  urine,  540 
phosphate-carbonate-thiocyanate      reagent, 

540 
Folin  and  Macallum's  microchemical  method  for 

ammonia,  521 

Folin,   Benedict  and   Myers'  method  for  deter- 
mination of  creatine,  529 
Folin-Benedict     method    for    determination    of 

creatine,  529 
Folin-Farmer    microchemical    method    for    total 

nitrogen  in  urine,  508 
Bock  and   Benedict's  modification 

of,  512 
Folin-Osborne  method  for  total  sulphur  in  urine, 

566 
Folin-Shaffer   method  for  determination  of  uric 

acid,  532 
Folin- Wright  method  for  total  nitrogen  in  urine. 

506 
Folin- Wu,  system  of  blood  analysis,  275 

method   for   determination    of    chlorides    in 

blood,  285 

creatine  in  blood,  281 
creatinine  in  blood,  280 
non-protein  nitrogen  in  blood,  277 
sugar  in  blood,  283 
urea  in  blood,  278 
uric  acid  in  blood,  281 

urine,  530 

Foods,  composition  of,  602 
purine  content  of,  605 

Foreign  substances  in  urinary  sediment,  482,  491 
Form  elements  of  blood,  248 
Formaldehyde,  as  milk  preservative,  341 

reaction  (Konto),  221 
Formaldehyde-H2SO4  test  (Morner),  85 
Formation  of  methyl-phenylfructosazone,  35 
Formic  acid,  26,  387,  415 

Formol  titration  method  of  Benedict-Murlin,  525 
of  Malfatti,  521 
of  Sorensen,  523 
Fractional  coagulation  of  proteins,  104,  116 

method  of  gastric  analysis,  150,  161 
Free  hydrochloric  acid,  56,  139,  156,  167 

tests  for,  156 

Freezing-point  of  bile,  206 
blood,  248 


INDEX 


659 


Freezing-point  of  milk,  329 

pancreatic  juice,  189 
urine,  382 
Frey-Gigon    method  for  amino-acid  nitrogen  in 

urine,  526 

Fridericia  apparatus,  320 
Fridericia's  method  for  determination  of  alkali 

reserve,  320 

Fructose,  Borchardt's  reaction  for,  35,  461 
in  urine,  461 

methyl-phenylhydrazine  test  for,  35 
Seliwanoff's  reaction  for,  34 
Fuchsin-frog  experiment,  365 
Fundus  glands,  138 
Furfural,  formation  of,  22 

solution,  preparation  of,  635 
Fusion  mixture,  preparation  of,  128 

Galactans,  20,  49,  50 

Galactase,  337 

Galactose,  19,  35.  33 1,  460 

experiments  on,  35 
Ganassini's  test,  398 
Gastric  acidity  and  the  use  of  indicators,  154  L^- 

automatic  regulation  of,  149,  153 
Gastric  analysis,  150,  176 

detection  of  bile  in,  174 
of  blood  in,  173 
of  food  rests  in,  175 
of  lactic  acid  in,  172 
of  mucus  in,  175 

determination  of  free  acidity  in,  167 
of  peptic  activity  in,    168 
of  total  acidity  in,  165 
of  tryptic  activity  in,  171 
examination  of  samples  in,  165 
fractional  method  of,  150,  162 
introduction  of  the  tube  in,  162 
Rehfuss  tube,  use  of  in,  150,  162 
retention  meal  in,  164 
test  meals  in,  164 
use  of  indicators  in,  154 
Gastric  digestion,  137 

conditions  essential  for,  144 

general  experiments  on,  144 

influence  of  bile  on,  146 

influence  of  different  temperatures  on, 

145 

influence  of  water  on,  137,  144 
most  favorable  acidity  for,  145 
power  of  different  acids  in,  146 
products  of,  140,  144 
Gastric  fistula,  137 
Gastric  juice,  138,  144 

acidity  of,  139,  150 

automatic  regulation  of,  149 
influence  of  water  on,  137,  143 

of  regurgitation  on,   139,    143, 

149,  153 

analysis  of,  150,  176 
artificial,  preparation  of,  144 
collection  of,  143 
composition  of,  138,  154 

enzymes  of,  138 
human,  collection  of,  143 
experiments  on,  147 
lactic  acid  in,  test  for,  172 
origin  of  hydrochloric  acid  of,  139 


Gastric  juice,  quantitative  analysis  of,  150,  176 
quantity  of,  137 
reaction  of,  138 
secretion  of,  13?,  138 

influence  of  meat  extractives  on,  147 
of    psychical    factors    on,   148 
of  water  on,  137,  143 
specific  gravity  of,  138 
Gastric  lipase,  138,  142 
Gastric  protease,  12 
Gastric  rennin,  139,  142,  147,  332,  338 

action  of,   upon  casein,   142,   147,   332, 

338 

experiments  on,  147,  338 
influence  of,  upon  milk,  147,  338 
in  gastric  juice,  absence  of,  142 
nature  of  action  of,  142,  331 
occurrence  of,  142 
Gastric  residuum,  154,  163 
analysis  of,  164 
composition  of,  154 
removal  of,  164 
Gelatin,  66,  67,  350,  35 1 
coagulation  of,  35 1 
decomposition  of,  66,  67 
experiments  on,  351 
formation  of,  350,  351 
Hopkins-Cole  reaction  on,  351 
Millon's  reaction  on,  351 
precipitation  of,  by  alcohol,  351 
alkaloidal  reagents,  351 
metallic  salts,  351 
by  mineral  acids,  351 
preparation  of,  from  cartilage,  353 

from  collagen,  350,  351 
salting-out  of,  35 1 
solubility  of,  351 

Gerhardt's  test  for  acetoacetic  acid,  454 
Gerhardt's  test  for  urobilin,  418 
Gies'  biuret  reagent,  preparation  of,  100 
Gliadin,  66,  93,  no,  in 
decomposition  of,  66 
preparation  of,  in 
tests  on,  in 
Globin,  66,  93,  112,  253 

decomposition  of,  66 
Globulins,  92,  107 

experiments  on,  108 
preparation  on,  108 
serum,  93,  249,  430,  441 
in  urine,  430,  441 
tests  for,  442 
vegetable,  108 
Glucoproteins   (see    Glycoproteins,   pp.   94.    m. 

350 

Glucosamine,  112 

Glucosazone,  crystalline  form  of,  Plate  III,  oppo- 
site p.  22. 
Glucose,  19,  21 

alcoholic  fermentation  of,  29 
assimilation  limit  of,  21,  60 1 
Bang's  method  for,  in  blood,  288 

in  urine,  542 
Barfoed's  test  on,  29 
Benedict  methods  for  determination   of  in 

urine,  538,  539,  549 

Benedict's  modification  of  Fehling's  test,  26, 
435 


66o 


INDEX 


Glucose,  Benedict's   modification  of  Lewis  Bene- 
dict method,  in  blood,  287 
Bertrand's  method  for,  545 

bismuth  tests,  27,  436 

differentiation  from  lactose  (Mathews),  40 

diffusibility  of,  23 

experiments  on,  21,  431 

Fehling's   method  for  determination  of,   in 
urine,  541 

Fehling's  test  on,  25,  433 

fermentation  of,  30,  437,  548 

Folin-McEllroy  test  for,  435 

Folin-McEllroy-Peck  Method  for,  540 

formation  of  caramel  from,  31 

formula  for,  21 

glycosuria  produced  by,  60 1 

Haines  test  on,  436 

hyperglycemia  produced  by,  598 

iodine  test  on,  23 

indigo  carmine  test  for,  437 

Molisch's  reaction  on,  21 

Moore's  test  on,  24 

Nylander's  test  on,  28,  436 

optical  activity  of,  31,  32 

Peters'  method  for,  543 

phenylhydrazine  test  on,  22,  431 

picric  acid  test,  29 

pola'riscopic  tests,  438,  549 

precipitation  by  alcohol,  23 

quantitative  determination  of,  in  blood,  283, 

287 
in  urine,  538 

reduction  tests  on,  24,  432 

solubility  of,  21 

tolerance  test,  290 

Trommer's  test  on,  25,  433 
Glucosidases,  4 
a-Glucosides,  4 
/3-Glucosides,  4 
Glucothionic  acid,  484 
Glutamic  acid,  68,  81,  189 

formula  for,  81 
Glutelins,  92,  109 

tests  on,  no 
Gluten,  preparation  of,  no 

tests  on,  no 
Glutenin,  93,  109,  no 

preparation  of,  no 

tests  on,  no 
Glycerol,  179,  180,  185 

borax  fusion  test  on,  186 

experiments  on,  185 

formula  for,  180 

hypochlorite-orcinol  reaction  for,  186 
Glycerol  extract  of  pig's  stomach,  preparation  of, 

144 

Glycerophosphoric  acid,  370,  371,  387,  416 
Glycine  (see  Glycocoll). 
Glycocholic  acid,  207 
Glycocholic  acid  group,  207 
Glycocoll,  64,  68,  70,  207 

crystalline  form  of,  214 

formula  for,  70,  207 

preparation  of,  214 
Glycocoll   ester   hydrochloride,    crystalline   form 

of,  71 
Glycogen,  20,  46,  359,  366 

experiments  on,  366 


Glycogen,  hydrolysis  of,  367 
in  embryos,  359 
influence  of  saliva  on,  367 
iodine  test  on,  367 
precipitation    by     ammoniacal     basic     lead 

acetate,  359 
preparation  of,  367 
Glycogenase,  4 
Glycolytic  enzymes,  3,  4 
Glycoproteins,  94,  in,  350 
experiments  on,  350 
hydrolysis  of,  350 
Glycosuria,  alimentary,  21,  431,  60 1 

by  glucose  ingestion,  21,  431,  60 1 
Glycosuric  acid,  412 
Glycuresis,  21,  414,  431 
Glycuronates,  conjugate,  26,  434,  456 

tests  for,  456 

Glycuronic  acid,  36,  37,  456 
Glycyl-glycine,  formation  of,  69 
Glycyl-tryptophane  test,  198,  202 
Glyoxylic  acid,  98 

formula  for,  98 
reaction  (Hopkins-Cole),  98 
Gmelin's  test  for  bile  pigments,  210,  448 

Rosenbach's  modification  of,  210,  448 
Gout,  blood  in,  251,  273,  274,  396 
Granular  casts  in  urinary  sediment,  485,  487 
Gregersen  and  Boas'  variation  of  benzidine  reac- 
tion, 267 

Green  stools,  cause  of,  225,  241 
Gross'  method  for  quantitative  determination  of 

tryptic  activity,  194 
Growth,  experiments  on,  580 

importance  of  vitamines  in,  580 
Growth-promoting  substances,  580 
Guaiac  solution,  preparation  of,  635 
Guaiac  test  on  blood,  238,  261,  265,  446,  447 
on  feces,  238 
on  milk,  337 
on  pus,  447 
on  urine,  446 
Guanase,  4 

Guanidine-or-amino-valeric  acid,  67,  69 
Guanidine  nitrogen,  63 
Guanine,  4,  124-126,  132,  358 
Guanine  chloride,  crystalline  form  of,  134 
Gum  arabic,  20,  49,  50 

Gums  and  vegetable  mucilage  group  of  carbo- 
hydrates, 20 

Gunning's  iodoform  test  for  acetone,  451 
Giinzberg's  reagent,  as  indicator,  156 
preparation  of,  156 

Haine's  test  on  sugar,  436 

Hair,  human,  348 

Halverson-Bergeim  method  for  calcium  in  blood, 
293 

Hammerschlag's  method  for  determination  of 
specific  gravity  of  blood,  263 

Harding  and  MacLean's  method  for  determina- 
tion of  amino-acid  nitrogen,  90 

Hart's  casein  method,  346 

Haser's  coefficient,  381,  504 

Hayem's  solution,  635 

Hay's  test  for  bile  acids,  212,  449 

Heintz  method  for  determination  of  uric  acid, 
394 


INDEX 


661 


Helicoprotein,  94 

Heller's  ring  test  for  protein,  102,  439 

Heller's  test  for  blood  in  urine,  446 

Hemagglutination,  253,  265 

Hemagglutinin,  253,  265 

Hematein  test  for  blood  in  feces,  228,  237 

Hematin,  112,  253,  257,  269 

acid-,  257,  303 

alkali-,  257,  302 

preparation  of,  269 

reduced  alkali-,  303 
Hematoidin,  208,  225,  227 

crystalline  form  of,  208,  225 

in  urinary  sediments,  475,  481 
Hematoporphyrin,  257,  376,  430,  459 

acid,  303 

alkaline,  302 

in  urine,  376,  430,  459 
Hematuria,     446 
Hemicellulose,  20,  49 

experiments  on,  50 

utilization  of,  by  animals,  49 
Hemin  crystals,  form  of,  268 

tests,  267,  269,  446 
Hemiurate,  478 

Hemochromogen,  112,  253,  257,  272,  202 
Hemoconein  (see  Blood  dust,  248,  259) 
Hemocyanin,  94,  112 

Hemoglobin,  94,  112,  252,  253,  257,  258,  265,  269, 
301 

carbon  monoxide,  257,  301 

decomposition  of,  253 

derivatives  of,  relationship  of,  257 

diffusion  of,  265 

met,  257,  302 

oxy,  253,  257,  269,  300 

quantitative  determination  of,  327 

reduced,  257,  301 
Hemoglobins,  94,  112 
Hemoglobinuria,  445 
Hemolysis,  248,  264 

Henderson  and  Palmer's  method  for  determina- 
tion   of    hydrogen    ion    concentration,    500 
Herter's  naphthaquinone  reaction  for  indole,  221 
Herter's  para-dimethylaminobenzaldehyde  reac- 
tion, 222 

Heterocyclic  nucleus,  64,  67,  68 
Heteroproteose,  96,  118 
Heteroxanthine,  387,419 
Hexone  bases,  79 
Hexosans,  20 

Hexoses,  19,  20  « 

Hippuric    acid,    71,    386,    405,    413,    480,    537, 
619 

crystalline  form  of,  406 

experiments  on,  406,  619 

Folin  and  Flander's  method  for  quantitative 
determination  of,  537 

formula  for,  405 

in  urinary  sediments,  480 

Lucke's  reaction  for,  407 

melting-point  of,  406 

Roaf's  method  for  crystallization  of,  407 

separation  of,  from  urine,  406 
solubility  of,  407 

sublimation  of,  407 

synthesis  of,  407,  619 

demonstration  of,  619 


Histidine,  64,  76 

hydrochloride,  crystalline  form  of,  77 
Knoop's  color  reaction  for,  77 
Histones,  93 

Hoffmann's  reaction  for  tyrosine,  85 
Homogentisic  acid,  388,  411,  434 

formula  for,  411 
Hopkin's    thiophene    reaction    for    lactic    acid, 

173 
Hopkins-Cole  reaction,  98 

on  solutions,  98 
on  solids,  106 

Hopkins-Cole  reagent,  preparation  of,  98 
Hopkins-Cole    reagent    (Benedict    modification), 

preparation  of,  98 
Hordein,  93,  no 

Horismascope  (see  Albumoscope,  102,  440) 
Hormones    definition    and    discussion    of,     184, 

335 

in  blood,  184 

Human  fat,  composition  of,  181 
gastric  juice,  143 

characteristics  of,  147 
collection  of,  143 
hair,  composition  of,  348 
milk,  differentiation  from  cow's,  332,  335 
Hunter  and  Givens'  modification  of  Kruger  and 

Schmidt's  method,  534 

Huppert-Cole  test  for  bile  pigments,    210,   448 
Hurthle's  experiment,  367 
Hartley's  test  for  acetoacetic  acid,  454 
Hyaline  casts  in  urinary  sediments,  482,  485 
Hydrobilirubin,  detection  of,  in  feces,  225,  238 

extraction  of,  239 
Hydrochloric  acid  solution,  N/io,  preparation  of, 

498 
Hydrochloric    acid    of    the    gastric    juice,    139, 

ISO 

origin  of,  theories  as  to,  139 
seat  of  formation  of,  138 
Hydrochloric  acid  test  for  formaldehyde  (Leach), 

340 

acid-zinc  chloride  solubility  test,  48 
Hydrogen     ion     concentration     and     titratable 

acidity,  158,  500 
mode  of  expressing,  155,  308  • 
of  blood,  determination  of,  326 
of  urine,  determination  of,  499,  500 
as  influenced  by  diet,  613 
by  acids,  615,  616 
by  alkali,  615,  616 
comparison     of,     with      titratable 

acidity,  158,  161 

determination    of,     by.    means     of 
indicators,  158,  500 

of  McClendon's  electrode, 

iSi 
Hydrogen  peroxide  in  urine,  387,  429 

detection  of,  in  milk,  341 
Hydrogenated  fat,  180 
Hydrogenation,  definition  of,  180 
Hydrolysis  of  cellulose,  47,  48 
cerebrin,  374 
dextrin,  46,  47 
glycogen,  367 
inulin,  45 
proteins,  63 
starch,  42,  44 


662 


INDEX 


Hydrolysis  of  sucrose,  40,  41 
/9-Hydroxybutyric  acid,  273,  305,  306,  310,  430 

450,  454,  552,  554 
Black's  reaction  for,  455 
formula  for,  455 
in  blood,  273,  306 
origin  of,  455 

polariscopic  examination  for,  456 
quantitative  determination  of,  in  urine. 

552,  554 

Hydroxymandelic  acid,  386,  412 
Hydroxyproline,  64,  66,  84 
Hyperacidity,  139,  167 

curve,  167 

Hypercholesterolemia,  250,  273,  292 
Hyperglycemia,  273,  598 

produced    by    carbohydrate    ingestion,    598 
by  physical  exercise,  600 
Hypoacidity,  139 

Hypobromite  solution,  preparation  of,  635 
Hypochlorite-orcinol  reaction  for  glycerol,  186 
Hypoxanthine,  126,  358,  361,  364,  387,  419 
chloride,  crystalline  form  of,  135 
formula  for,  126,  364 
oxidase,  126 

Hypoxanthine  silver  nitrate,  crystalline  form  of, 
369 

Ichthulin,  94 
Ignotine,  358,  364 

formula  for,  364 
Imid  bonds,  69 

imid  nitrogen,  63 
I  minazolylethy  lamine  ,217 
Iminazolylpropionic  acid,  217 
Index  of  acid  excretion  in  urine,  determination  of, 

324 
Indican,  215,  403,  558 

formula  for,  215,  404 
Jaffe's  test  for,  404 
Jolles'  reaction  for,  405 
Obermayer's  test  for,  405 
origin  of,  215,  404 
Indicator  method  for  determination  of  hydrogen 

ion  concentration,  161,  500 
solutions,     preparation    of,     161 

use  of,  161 

Indicators,  experiments  on,  154 
table  of,  156,  161 

tabulation  of  results  of  tests  on,  157 
use  of,  154 

in  gastric  analysis,  154 
Indigo-blue,  212,  405 

formula  for,  212,  405 

Indigo  carmine  test  for  sugar  in  urine,  437 
Indigo  in  urinary  sediments,  473,  481 
Indole,  211,  217,  221,  240,  245 
formula  for,  211 
in  feces,  quantitative  determination  of,  by 

Bergeim's  method,  245 
origin  of,  211 
test  for,  221,  240 

/3-Indole-a-amino-propionic  acid,  67.  ?6 
Indolylacetic  acid,  217,  467 
Indolylpropionic  acid,  217 
Indoxyl,  215 

formula  for,  215,  405 
origin  of,  215 


Indoxyl,  potassium  sulphate  (see  Indican,  p.  215, 

404,  558) 
Indoxyl-sulphuric  acid,  215,  386,  402 

formula  for,  215,  403 
Influence  of  purine-free  and  high  purine  diets, 

604 

Infraproteins  (see  Metaproteins,  94,  114,  115) 
Inorganic  elements  in  feces,  absorption  of,  624 

physiological  constituents  of  urine,  387,  402 
Inosinic  acid,  358,  364 

formula  for,  364 
Inositol,  19,  358,  430,  465 
formula  for,  465 
in  urine,  430,  440,  465 
Intestinal  digestion,  198 
juice,  198 

enzymes  of,  198,  199,  200-204 

preparation  of,  200—204 
Inulase,  4,  45 
Inulin,  20,  45 

action  of  amylolytic  enzymes  on,  45 
Fehling's  test  on,  45 
hydrolysis  of,  45 
iodine  test  on,  45 
reducing  power  of,  45 
solubility  of,  45 
sources  of,  45 
Inversion,  40,  42 

Invertase  (see  Sucrase,  4,  40,  198,  202) 
Invertases,  experiments  on,  202 
Invertin  (see  Sucrase,  4,  40,  198,  202) 
Inverting  enzymes,  3,  198,  202 
Invert  sugar,  40 
Iodide  of  dextrin,  44 

of  starch,  46 
Iodine  absorption  test,  186 

test  for  starch  and  dextrin,  44,  45,  46,  48 

50,  55 

for  urobilin,  418 

Iodine-sulphuric  acid  test  for  cholesterol,  213,  374 
lodine-zinc-chloride  reaction,  48 
lodoform  test  for  alcohol,  30 

for  acetone  (Lieben),  451 
lodothymol  compound,  451 
"lothion,"  28,  437 

Iron,  reduced,  influence  on  color  of  feces,  241 
in  blood,  264 

detection  of,  264 
in  bone  ash,  355 

detection  of,  355 
in  protein,  62 
in  urine,  429,  577 

detection  of,  429 
determination  of,  577 
Isoleucine,  64,  79 
Isomaltose,  19,  39 

Isopropylmetacresol  (see  Thymol,  384) 
Iso valeric  acid,  217 

Jacoby-Solms  method,  170 

Jaffe's  reaction  for  creatinine,  402 

Jaffe's  test  for  indican,  404 

v.  Jaksch-Pollak  reaction  for  melanin,  466 

Jejunum,  epithelial  cells  of,  188 

Jolles'  reaction  for  indican,  405 

Juice,  gastric,  137,  ISO 

pancreatic,  188 

intestinal,  198 


INDEX 


663 


Kafirin,  no 

Kantor  and  Gies's  biuret  paper,  100 

Kastles  peroxidase  reaction,  338 

Kephalin,  370,  372 

Kephyr,  39 

Keratin,  93,  in,  348 

composition  of,  from  different  sources,  348 
experiments  on,  349 
solubility  of,  349 
sources  of,  348 
sulphur  content  of,  348 
Ketone,  19,  24 
Ketose,  19 

Kidney  efficiency  test,  470,  471    . 
Killian,  carbohydrate  tolerance  test,  290 
Kjeldahl  method  for  determination  of  nitrogen, 

504 

Kjeldahl-Folin- Farmer  nitrogen  method,  506 
Knoop's  color  reaction  for  histidine,  77 
Kober  nephelometer-colorimeter,  297 
Konto's  reaction  for  indole,  221 
Koprosterol  in  feces,  227,  228,  235 
Koumyss,  39 

Kraut's  reagent,  preparation  of,  375,  636 
Kreosotal  and  tests  for  pentose,  458 
Kruger  and  Schmidt's  method  for  the  quantita- 
tive   determination    of    pu- 
rine  bases,  533 
of  uric  acid,  533 

Kwilecki's  modification  of  Esbach's  method,  55 1 
Kynurenic  acid,  386,  412 
formula  for,  412 
isolation  of,  from  urine,  412 
quantitative  determination  of,  412 

Laccase,  5 

Lactalbumin,  93,  336,  339,  346 

quantitative  determination  of,  346 
Lactase,  4,  198,  199,  203 
experiments  on,  203 
lactation,  variation  in  milk  during  different 

stages  of,  334 

Lactic  acid,  39,  139,  162,  172,  330,  358,  359 
Lactic  acid,  ether-ferric  chloride  test    (Strauss) 
for,  172 

fermentation,  39,  330 
ferric  chloride  test  (Kelling)  for,  173 
Hopkins'  thiophene  reaction  for,  173 
in  muscular  tissue,  358,  359 
in  stomach  contents,  172 
tests  for,  172 
Uffelmann's  test  for,  173 
Lactochrome,  336,  417 
Lacto-globulin,  336 
Lactometer,  determination  of  specific  gravity  of 

milk  by,  341 

Lactosazone,  crystalline  form  of,  Plate  III,  oppo- 
site p.  22 

Lactoscope,  Feser's,  344 
Lactose,  19,  39,  329,  335,  340,  347 

differentiation  from  lactose,  40,  438 
experiments  on,  39,  340 
fermentation  of,  39,  335 
in  urine,  430,  459 

quantitative  determination  of,  346,  540 
Laiose  in  urine,  466 
"Laked"  blood,  248,  264 
Laky  blood,  264 


Lanolin,  181, 151 

Laurie  acid,  329 

Leach's  hydrochloric  acid  test  for  formaldehyde, 

340 
Lecithin,  94,  250,  370 

acrolein  test  on,  373 

decomposition  of,  371 

experiments  on,  373 

formula  for,  371 

microscopical  examination  of,  373 

osmic  acid  test  on,  373 

preparation  of,  373 

test  for  phosphorus  in,  373 
Lecithoproteins,  94,  113 
Legal's  reaction  for  indole,  221 

test  for  acetone,  452 

Le  Nobel  reaction  for  acetoacetic  acid,  453 
Leucine,  66,  68,  78,  84,  86 

crystalline  form  of  impure,  480 
pure,  79 

experiments  on,  86 

formula  for,  78 
»   in  urinary  sediments,  480 

microscopical  examination  of.  86 

separation  Of,  from  tyrosine,  85 

solubility  of,  86 

sublimation  of,  86 
Leucocytes,  248,  258 

number  of,  per  cubic  millimeter,  258 

size  of,  258 

variation  in  number  of,  258 
Leucocytosis,  258 
Leucosin,  102 

Leucyl-alanyl-glycine,  formation  of,  69 
Leucyl-glycyl-alanine,  56 
Leucyl-leucine,  formation  of,  69 
Levo-a-proline,  82 

Levulosazone,  crystalline  form  of,  Plate  III,  op- 
posite, p.  22 

Levulose  (see  Fructose),  19,  34 
Lewis  and  Benedict's  method  for  sugar  in  blood, 

Benedict's  modification  of,  287 
Lichenin,  20,  46 
Lieben's  test  for  acetone,  452 
Lieberktihn's  jelly  (see  Alkali  metaprotein,  p.  115) 
Liebermann-Burchard   test   for  cholesterol,  213, 

374 

Linoleic  acid,  180 
Lipase,  gastric,  138,  142 
Lipase,  pancreatic,  5,  13,  181,  191,  196 
copper  soap  test  for,  197 
ethyl-butyrate  test  for,  196 
experiments  on,  13,  196 
influence  of  "bile  on,  192 
litmus-milk  test  for,  196 
Lipases,  5,  13,  181,  191,  196 

autolytic,  5 

experiments  on,  13,  196 

pancreatic,  13,  181,  191,  196 

vegetable,  13 

Lipemia,  blood  in,  273,  274 
Lipeses,  9 
Lipins,  370 

Lipoids  of  nervous  tissue,  370,  373 
Lipolytic  enzymes  (see  Lipases,  p.  5,  I3,,i8i,  191, 

197) 

'"Litmus-milk"  test  for  pancreatic  lipase,  197 
Litmus  milk  powder,  636 


664 


INDEX 


Long's  coefficient,  381,  504 
Lticke's  reaction  for  hippuric  acid,  407 
Lugol's  solution,  preparation  of,  636 
Lyle-Curtman  guaiac  "procedure,"  237 

reagent,  237,  458,  460,  637 
Lymph,  249,  263 
Lysine,  68,  80,  142,  190 
Lysine  picrate,  crystalline  form  of,  81 

Magnesia  mixture,  preparation  of,  637 
Magnesium  balance,  preparation  of,  625 
in  bone,  detection  of,  355 
in  urine,  387,  427 

quantitative    determination     of, 

575 

nitrate  solution,  637 
phosphate  in  urinary  sediments,  474, 

481 
Malfatti's  formol  titration  method  for  ammonia  in 

urine,  521 
Maltase,  4,  56,  199,  204 

experiments  on,  204 

Maltosazone,  crystalline  form  of,  Plate  III,  op- 
posite p.  22 
Maltose,  19,  38 

experiments  on,  38 
structure  of,  38 
Marsh  apparatus,  463 

cut  of,  463 

method  for  arsenic,  463 
Marshall's  clinical  urease  method  for  estimation 

of  urea  in  urine,  518 
Mastication,    defective,    influence    of,    on    food 

residues  in  feces,  230,  623 
Mathews,  differentiation  of  lactose  and  glucose, 

40,  438 

Marvein,  use  of,  as  indicator,  161 
McClendon's  electrode,  determination  of  H  ion 

cone,  by,  151 

McCrudden's  method  for  determination  of  cal- 
cium, 574 
of  magnesium,  574 

McLean  and  Van  Slyke's  method  for  determina- 
tion of  chlorides  in  blood,  290 
Melanin  in  urine,  430,  466,  475 
tests  for,  466 

urinary  sediments,  475,  482 
Melting-point  apparatus,  186 

of  fats,  determination  of,  186 
Mercury  in  urine,  464 

detection  of,  465 

Metabolic  product  nitrogen,  230,  622 
Metabolism,  519 
basal,  328 
experiments,  580 

balance  of  income  and  outgo  in,  prepa- 
ration of,  625 
collection  and  preservation  of  feces  in, 

621 

separation  of  feces  in,  620 
urine  in,  384,  598 
Folin's  theory  of,  612 
in  acidosis,  304,  609 
in  fasting,  618 
in  gout,  604,  607 

influence  of  acids  on,  309,  615,  616 
of  alkalies  on,  309,  615,  616 
of  defective  mastication  on,  623 


Metabolism,  influence  of  digestion  on,  610 

of   fats   and   carbohydrates   as   protein 

sparers  in,  612 
of  high  calorie,  non-nitrogenous  diet  on, 

617 
indigestible,    non-nitrogenous    material 

on,  622 

of  water  on,  607 

of  acid-forming  and  base-forming  foods,  613 
of  ammonium  benzoate,  619 
of  carbohydrates,  598-602,  612 
of  energy,  612,  617,  618 
of  fat,  602,  612 

of  inorganic  elements,  624,  625 
of  nitrogen   and   sulphur  as   influenced  by 

diet,  610 
of  proteins,  602 

time  relations  of,  602 
of  purines,  604-607 
on  "salt-free"  diet,  609 
on  salt-rich  diet,  609 

relation  of  bacterial  nitrogen  of  feces  to,  621 
of  metabolic  product  nitrogen  of  feces 

to,  622 

study  of  creatinine  elimination  in,  607 
time  relations  of  protein,  602 
Menstrual  blood,  260 
Metaproteins,  94,  114 
acid,  94,  114,  115 
alkali,  94,  114,  115 
experiments  on,  115 
precipitation  of,  115 
sulphur  content  of,  115 
Methemoglobin,  257,  302 
Methylene  blue,  146 

reaction  (Russo),  470 
Methyl-mercaptan,  215 

Methyl  orange,  use  of,  as  indicator,  161,  522,  638 
red,  use  of,  as  indicator,  161,  515,  637 
violet,  use  of,  as  indicator,  161 
Methyl-pentose  (see  Rhamnose,  p.  19) 
Methylphenylfructosazone,  formation  of,  35 
Methylphenylhydrazine,  35 
i-methylxanthin,  387,  419 
Mett's    method    for    determination    of    peptic 

activity,  168 

Mett's  tubes,  preparation  of,  169 
Micro-organisms  in  urinary  sediments,  480,  489 
in  feces,  224,  228 
in  intestine,  224,  228 
Milk,  329 

ash  of  human  and  cow's  334,  345 

calcium  phosphate  from,  340-' 

casein  of,  329,  331,  336,  339 

citrates  in,  329 

composition  of,  in  relation  to  rate  of  growth 

of  young,  335 

composition  of  human  and  cow's  333,  335 
constituents  of,  329,  330 
curds,  photographs  of,  332 
detection  of  calcium  phosphate  in,  351 
lactose  in,  351 
preservatives  in,  352 
difference  between  human  and    cow's,  333, 

334.  337 

summer  and  winter,  329 
experiments  on,  33? 
formation  of  film  on,  330,  336 


INDEX 


665 


Milk,  freezing-point,  330 
guaiac  test  on,  337 

human  and  cow's,  differentiation,  333,  334,337 
influence  of  rennin  on,  142,  147,  331 
isolation  of  fat  from,  340,  342 
Kastle's  peroxidase  reaction  on,  337 
lactic  acid  from,  330 
lactose  in,  329,  33O,  335,  339 
crystalline  form  of,  335 
fermentation  of,  330 
microscopical  appearance  of,  33 1,  337 
paracasein  from,  331    333 
powder,  330 

preparation  of  casein  from,  339 
properties  of  casein  of,  331,  336,  339 
quantitative  analysis  of,  341 
reaction  of,  330,  336 

separation  of  coagulable  proteins  of,  339 
serum,  330 
souring  of,  330 
specific  gravity  of,  330,  336 
variation  in  composition  of,  during  different 

periods  of,  lactation,  334 
vitamines  in,  329 
"witches,"  335 
Millon's  reaction,  97 

reagent,  preparation  of,  97,  638 
Molisch's  reaction,  21 

reagent,  638 

Molybdate  solution,  preparation  of,  636 
Monamino  acid  nitrogen,  63 
Monosaccharides,  19,  20 
Barfoed's  test  for,  29 
classification  of,  19 
Morner's  reagent,  preparation  of,  85,  638 

test  for  tyrosine,  85 
Motor  and  functional  activities  of  the  stomach, 

146 
Mucic  acid,  36,  40,  459,  460, 

test,  36,  40,  459,  460 
Mucin,  54,  57,  94,  112 
biuret  test  on,  58 
hydrolysis  of,  58 
isolation  of,  from  saliva,  58 
Millon's  reaction  on,  58 
Mucins,  54,  88,  112 

experiments  on,  350 
hydrolysis  of,  350 
in  urine,  414,  444 
preparation  of,  from  tendon,  350 
Mucoids,  94,  112,  349,  350 
Murexide  test,  397 
Muscle  plasma,  356,  364 

m        formation  of  myosin  clot  in,  357,  365 
fractional  coagulation  of,  357,  365 
preparation  of,  364 
reaction  of,  360,  365 
Muscular  tissue,  357 

ash  of,  smooth  and  striated,  363 
commercial  extracts  of,  363 
experiments  on  "dead,"  366 

"living,"  364 
extractives  of,  358,  367 
fatigue  substances  of,  363 
lormulas  of  nitrogenous  extractives  of, 

364 

glycogen  in,  358,  359,  366 
Muscular  tissue,  involuntary,  357 


Muscular  tissue,  lactic  acid  in,  358,  359,  365 
magnesium  in,  demonstration,  367 
nonstriated,  357 

phosphate  in,  demonstration  of,  367 
pigment  of,  363 
preparation  of  glycogen  from,  366 

muscle  plasma  from,  364 
proteins  of,  357,  364,  365,  366 
reaction  of  living,  360,  365 
rigor  mortis  of,  357,  358 
separation  of  extractives  from,  367 
striated,  357 
voluntary,  357 
Myers  and  Wordell,  determination  of  cholesterol, 

291 

Myohematin,  363 
Myosan,  95,  366 

formation  of,  366 
Myosin,  357,  366 

biuret  test  on,  366 
coagulation  of,  366 
preparation  of,  366 
solubility  of,  366 
Myosinogen,  35^,  365 
Myristic  acid,  329 
Myristin,  180 
Myrtle  wax  (see  Bayberry  tallow,  184) 

a-Naphthol  reaction,  21 

solution,  21,  638 
Naphthoresorcinol     reaction     for     glycuronates 

(Tollens),  456 

Nencki  and  Sieber's  reaction  for  urorosein,  467 
Neosine,  358,  364 

formula  for,  364  . 
Nephelometer,  Bloor,  cut  of,  295 
description  of,  295 
Kbber,  cut  of,  297 

Nephelometric,  determination  of  fat  in  blood,  299 
in  milk,  344 

proteins  in  milk,  345 

in  urine,  551 

Nephelometric  methods,  294,  299,  344,  345,  551 
Nephritis,  blood  in,  251,  273,  274,  278,  281 
Nephrorosein  in  urine,  467 
Nervous  tissue,  370 

constituents  of,  370 

experiments  on  lipoids  of,  373 

lipoids  of,  370,  373 

percentage  of  water  in,  370 

phosphorized  fats  of,  370 

proteins  of,  370 
Nessler's  solution,  638 
Neurine,  215 

Neumann's  method  for  total  phosphorus,  570 
Neurokeratin,  370 
Neutral  fats,  180,  181,  183 
Neutral  olive  oil,  preparation  of,  183,  639 
Neutral  red,  use  of,  161,  639 
Neutral  sulphur  compounds,  386,  409 
Ninhydrin  reaction,  100 
Nippe's  hemin  test,  267 
Nitrates  in  urine,  387,  429 
Nitric  acid  test  (Heller),  102,  440 

for  phenol,  223 

Nitric  acid-MgSO4  test  (Roberts),  103,  440 
Nitrilase,  8 
Nitrilese,  8 


666 


INDEX 


Nitrites  in  saliva,  test  for,  58 
Nitrogen,  62,  63 

forms  of,  in  protein  molecule,  63 
importance  of,  in  sustaining  life,  63 
in  urine,  quantitative  determination  of,  522 
Nitrogen  distribution,  calculation  of,  523 
Nitrogen  iodide,  formation  of,  45 1 
Nitrogen  "lag,"  602 

metabolic  product,  230,  622 
"partition,"  506,  608,  610 
Nitrogenous  extractives  of  muscular  tissue,  358, 

367 

formulas  for,  364 

^-Nitrophenol,  use  of,  as  indicator,  161,  501 
Nitroprusside  reaction  for  indole  (Legal),  221 
Nitroprusside  test  for  creatinine  (Weyl),  402 
Nitroprusside-acetic     acid    test     for     creatinine 

(Salkowski),  402 
Nitroso-indole  nitrate  test,  222 
Nitrosothymol,  formation  of  in  Heller's  test,  440 
Non-nitrogenous  extractives  of  muscular  tissue, 

358 
Non-protein   nitrogen    of  blood,    251,    273,   277, 

278 
Normal  urine,  376,  386,  388 

characteristics  of,  376 
constituents  of,  386,  388 
experiments  on,  402-429 
Novaine,  358 

formula  for,  364 
Nubecula,  414,  444 
Nucleases,  5 

experiments  on,  133 
Nucleic  acid, '1 23-1 27,  130-136 
decomposition  of,  123-125 
experiments  on,  130-136 
from  yeast,  formula  for,  124 
Nucleicacidase,  5,  125 
Nucleins,  122,  123,  144,  604 
Nucleoproteins,  94,  m.  122,  127-131,  206,  210, 

239,  370,  386,  414.  430,  444 
decomposition  of,  122—123 
experiments  on,  127—130 
from  yeast,  127 

preparation  of,  127 

protein,    carbohydrate   and    phosphoric 

radicals  in,  129 
tests  dn,  128 
thymus,  preparation  of,  129 

experiments  on,  129 
in  bile,  206,  210 
in  feces,  239 
in  nervous  tissue,  370 
in  urine,  386,  414,  430,  444 

test  for,  444 
occurrence  of,  122 
Ott's  precipitation  test  for,  444 
Nucleosidase,  5,  125 
Nucleoside,  124 

Nucleotidase,  125  . 

Nucleotide,"  124 
Nylander  reaction,  28,  436 
Nylander  reagent,  preparation  of,  28,  436 

Obermayer's  test  for  indican,  405 

reagent,  preparation  of,  405 
Oblitine,  358 
"Occult"  blood  in  feces,  228,  236 


"  Occult  "  blood  in  feces,  tests  for,  236 
Olein,  1 80,  329 
Olive  oil,  183 

emulsification  of,  183 
neutral,  preparation  of,  183 
Oliver's  peptone  test  for  bile  acids,  212 
Optical  methods,  30-33 
Orcinol-HCl  reaction  (Bial),  37,  458 
Orcinol  test,  37,  458 

Organic  physiological  constituents  of  urine,  386 
Organized  ferments,  i 
Organized  urinary  sediments,  472,  480 
Ornithine,  64,  217 

Ortho-tolidin  test  for  blood,  173,  236,  266,  446 
Osborne-Folin  method  for  determination  of  total 

sulphur  in  urine,  566 
Ossein,  354 

preparation  for,  354 
Osseoalbumoid,  354 
Osseomucoid,  94,  112,  354 

chemical  composition  of,  112 
Osseous  tissue,  354 

experiment  on,  355 
Ott's  precipitation  test  for  detection  of  nucleo- 

protein  in  urine,  444 
Ovalbumin,  92 
Ovoglobulin,  93 

Oxalated  plasma,  preparation  of,  271 
Oxalic  acid,  386,  408 

experiments  on,  408 

formula  for,  408 

in  urine,  386,  408 

standard  solution  of,  preparation  of,  49? 

quantitative  determination  of,  562 
Oxaluria,  408 
Oxaluric  acid,  386,  410 
Oxamide,  99 
Oxidases,  5,  14.  336 

experiments  on,  14 
Oxyacids,  215,  223,  386,  4" 

tests  for,  223 
/3-Oxybutyric  acid    (see    0-hydroxybutyric    acid, 

273,  305,  306,  310,  430,  450,  454.  552,  554) 
Oxygen  in  blood,  determination,  of,  327 
Oxyhemoglobin,  63,  253,  257,  258,  269 

crystalline  forms  of,  254-257 

Reichert's  method  for  crystallization  of,  269 
Oxymandelic   acid    (see    Hydroxymandelic   acid, 

386,  412) 

Oxyproline  (see  hydroxyproline,  64,  66,  84) 
Oxyproteic  acid,  386,  409,  466,  568 

Palmitic  acid,  179,  180,  184,  185 
crystalline  form  of,  185 
experiments  on,  185 
formula  for,  180 
preparation  of,  185 
Palmitin,  180 
Pancreatic  amylase,  4,  n,  190,  195 

digestion  of  raw  starch  by,  191,  195 

inulin  by,  195 
experiments  on,  u,  194 
influence  of  bile  upon  action  of,  195 
most  favorable  temperature  for  action 

of,  195 
Pancreatic'  digestion,  188 

general  experiments  on,  193 
products  of,  189,  192 


INDEX 


667 


Pancreatic  insufficiency,  Schmidt's  nuclei  test  for, 

240 

Pancreatic  juice,  122,  188,  189,  190,  192 
artificial,  preparation  of,  192 
daily  secretion  of,  189 
enzymes  of,  189 
freezing-point  of,  189 
mechanism  of,  secretion  of,  188 
reaction  of,  189 
solid  content  of,  189 
specific  gravity  of,  189 
Pancreatic  lipase,  5,  13,  181,  191 
copper  soap  test  for,  197 
ethyl-butyrate  test  for,  197 
experiments  on,  13,  196 
litmus-milk  test  for,  197 
Pancreatic    protease    (see    Trypsin,    pp.    5,.  12, 

189) 
Pancreatic  rennin,  5,  189,  192,  197 

experiments  on,  197 
Papain,  5,  13 
Papayotin  (see  Papain) 
Paracasein,  331,  333 
Para-cresol-sulphuric  acid,  386,  402 
Paradimethylamino  benzaldehyde  solution,  prepa- 
ration of,  639 

Paralactic  acid,  250,  330,  359,  387,  415 
Paramyosinogen,  357 
Paranucleoprotagon,  370,  373 
Paraoxyphenylacetic  acid,  215,  217,  386,  411  . 
Paraoxy-0-phenyl-a-amino-propionic  acid,  68,  73, 

85 

Paraoxyphenylpropionic  acid,  215,  217,  386,  411 
Paraphenylenediamine  hydrochloride,  341 
Parasites,  230,  482,  491 
Paraxanthine,  387,  419 
Parietal  cells,  138 
Parotid  glands,  characteristics  of  saliva  secreted 

by,  53 

Pathological  constituents  of  urine,  430 
Pathological  urine,  376,  430 
constituents  of,  430 
experiments  on,  431 

"Partition"  of  nitrogen  and  sulphur  in  urine,  610 
Pektoscope,  382 
Pentamethylenediamine,  217 
Pentapeptides,  65,  94 
Pentosans,  20,  35,  49,  50 
Pentosazone,  crystals  of,  457 
Pentoses,  19,  36 

experiments  on,  36 
in  urine,  430,  457 
tests  for,  457 
Pepsin  (see  Gastric  Protease),  5,  12,  140,  144-146, 

1 68 
action  of,  influence  of  bile  upon,  146 

influence  of  different  acids  upon,  146 
influence  of  metallic  salts  upon,  146 

temperature  upon,  145 

Pepsin,   conditions  essential  for  action   of,    144 
differentiation  of,  from  pepsinogen,  140,  145 
digestive  properties  of,  140 
formation  of,  140 

most  favorable  acidity  for  action  of,  145 
presence  of,  in  intestine,  141 
proteolytic  action  of,  140 
Pepsin-hydrochloric  acid,  145 
Pepsin-rennin  controversy,  142 


Pepsinogen,  6,  140,  144,  145 

differentiation  of,  from  pepsin,  140,  145 
extract  of,  preparation  of,  144 
formation  of,  140 
Peptases,  5 

Peptic  activity,   Given's  modification  of  Rose's 

method    for    determination    of,     171 

Mett's  method  for  the  determination  of, 

168 

Rose's  method  for  determination  of,  170 
Peptic  proteolysis,  140 

products  of,  140 

relation  of,  to  tryptic  proteolysis,  141 
Peptides,  65,  69,  95,  "9 
Peptone,  64,  70,  95,  "7 
ampho,  94,  118 
anti,  118 

differentiation  of,  from  proteoses,  118 
experiments  on,  118,  119 
in  urine,  430,  442 
test  for,  443 

separation  of,  from  proteoses,  119 
Periodide  test  for  choline,  374 
Permutit,  639- 

use  of  in  determining  ammonia,  522 
Peroxidase  reaction,  Kastle's,  for  milk,  338 
Peroxidases,  5,  14,  IS,  337,  338 
Peters'  method  for  sugar  determination,  543 
Pettenkofer's  test  for  bile  acids,  211,  449 

Mylius's  modification  of,  211,  449 
Phenaceturic  acid,  387,  4i6 
Phenol,  216,  222,  403,  559.  561 
excretion  of-,  403,  561 

quantitative  determination  of,  in  urine,  559 
tests  for,  222 
Phenolphthalein  as  indicator,  156,  157,  160,  161, 

165,  499 

preparation  of,  161,  640 
test  for  blood  in  feces,  237 
Phenol  potassium  sulphate  215,  403,  558 
Phenolsulphonephthalein    test    for    kidney    effi- 
ciency, 470 

Phenol-sulphuric  acid,  386,  402 
Phenylacetic  acid,  217 
Phenyl-a-amino  propionic  acid,  68,  72 
Phenylalanine,  64,  66,  68,  72,  217 
Pheriylethylamine,  217 

Phenylglucosazone,    22    and    Plate    III    opposite 
Phenylhydrazine,  22 

acetate  solution,  preparation  of,  22 
mixture,  preparation  of,  22 
reaction,  22,  23,  431 
Phenyllactosazone,  crystalline  form  of,  Plate  III, 

opposite  p.  22 
Phenylmaltosazone,  crystalline  form  of  Plate  III, 

opposite  p.  22 
Phenylpropionic  acid,  217 
Phloroglucinol-HCl  reaction,  35,  37,  458,  561 
Phosphate-carbonate    mixture,    Folin-McEllroy, 

535 
Phosphate  carbonate-thiocyanate  mixture,  Folin- 

McEllroy-Peck,  540 

Phosphate  solutions  and  hydrogen  ion  concen- 
tration, 157,  159,  160,  162,  309,  378,  501 
Phosphates  in  urine,  378,  424.  568 
detection  of,  424 
experiments  on,  424 
quantitative  determination  of,  568 


668 


INDEX 


Phosphatase,  9 
Phosphatese,  9 

Phosphatides,  206,  299,  329,  370,  425 
Phosphocarnic  acid,  358,  364,  387,  416 
Phosphonuclease,  135 
Phosphoproteins,  94,  95,  112,  329 
Phosphorized  compounds  in  urine,  387,  416 
Phosphorus  in  urine,  determination  of,  568 

organic,  test  for,  128 

Phosphotungstic  acid  reaction  (Folin),  398 
precipitation  test  for  proteose 

(v.  Aldor),  443 

Physiological  constituents  of  urine,  386 
Phytase,  5 

Phytin,  5  „ 

Picric  acid  reaction  for  creatinine  (Jaffe),  402 

test  for  glucose,  29 

Pigments  of  urine,  376,  387,  417,  466,  467 
Pine  wood  test  for  indole,  222 
Piria's  test  for  tyrosine,  85 
Plasma  of  blood,  248 

of  muscle,  357,  364 
Plasmaphaeresis,  252 
Polariscope,  use  of,  31 

in  detection  of  conjugate  glycuronates, 

457 

0-hydroxybutyric  acid,  456 
in  determination  of  glucose,  31,  549 
Polypetides,  65,  69,  95 
Polysaccharides,  20,  42 
classification  of,  20 
properties  of,  42 

Posner's  modification  of  biuret  test,  100 
Potassium   hydroxide    test   for   blood    in   urine 

(Heller),  446 
Potassium  hydroxide  testfor  pus  in  urine  (Donn6), 

448 
indoxyl-sulphate  (see  Indican,  pp.  215,  403, 

558) 

determination  of,  558 
formula  for,  215,  404 
origin  of,  215,  403 
tests  for,  404,  405 
Potassium  in  urine,  387,  427,  576 

quantitative  determination  of,  576 
Powdered  milk,  329 

Primary  protein  derivatives,  64,  94,  H3. 
Primary  proteoses,  118 

Products  of  protein  hydrolysis,  64,  66,  67,  68,  70, 
.   189 
Prolamins,  93,  no 

classification  of,  93 
preparation  of,  in 
tests  on,  in 
Proline,  64,  66,  67,  82,  no,  141,  189 

crystalline  form  of  copper  salt  of,  83 
crystalline  form  of  laevo-a-,  83 
Prosecretin,  188 
Protagon,  370,  371 

preparation  of,  373 
structure  of,  372 

Protamines,  classification  of,  93,  95 
Proteans,  95,  H3 
Protease,  gastric,  5.  12,  140,  144 
experiments  on,  12,  144 
pancreatic,  5,  12,  189 

experiments  on,  12,  192 
vegetable,  5,  13 


Proteases,  5,  12 

experiments  on,  12 

Protective  enzymes  (see  Defensive  Enzymes,  3) 
Proteid  (see  Proteins) 
Protein  content  of  foods,  602 

derivatives,  primary,  64,  94,  113 

secondary,  64,  95,  117 
metabolism,  time  relations  of,  602 

influence  of  water  on,  607 
utilization,  determination  of,  623 
Protein-coagulating  enzymes,   5,    142,    192,    259, 

331 

Protein-cystine,  76 
Protein-sparing  action  of  fat  and  carbohydrate, 

612 
Proteins,  62,  91,  430,  438 

acetic  acid  and  potassium  ferro-cyanide  test 

for,  103 

action  of  alkaloidal  reagents  on,  102 
of  metallic  salts  on,  102 
mineral  acids,  alkalies  and  organic  acids 

on,  102 

biuret  test  on,  99 
chart  for  use  in  review  of,  120 
chemical  composition  of,  62 
classification  of,  93,  95 
coagulated,  95,  "5 

biuret  test  on,  117 
formation  of,  115 
Hopkins-Cole  reaction  on,  117 
Millon's  reaction  on,  117 
quantitative  determination  of,  550 
solubility  of,  117 
xanthoproteic  reaction  on,  117 
coagulation,  influence  of  salts  upon,  116 
coagulation  or  boiling  test  for,  104 
color  reactions  of,  97 
conjugated,  94,  95,  i«»  122 
classes  of,  94,  in 

experiments  on,  58,  127,  269,  300,  339 
nomenclature  of,  94,  in 
occurrence  of,  94,  in 
decomposition  of,  63,  66,  67 
by  hydrolysis,  64 
by  oxidation,  63 
products  of,  63,  66,  67,  70 
experiments  on,  84 
separation  of,  84. 
study  of,  63,  66,  84 
derived,  94,  113 
formation  of  fat  from,  182 
formulas  of,  63 
Heller's  ring  test  on,  102 
Hopkins-Cole  reaction  on,  98 
importance  of,  to  life,  62 
in  urine,  430,  438,  550 

determination  of,  550 
test  for,  439 
Millon's  reaction  on,  97 
of  milk,  336,  339,  345,  346 
molecular  weights  of,  63 
ninhydrin  reaction  on,  100 
Posner's  reaction  on,  100 
precipitation  of,  by  alcohol,  105 
alkaloidal  reagents,  102 
metallic  salts,  102 
mineral  acids,  102 
precipitation  reactions  of,  101 


INDEX 


669 


Proteins,  quantitative  determination  of,  in  milk, 
345,  346 

review  of,  120 

Robert's  ring  test  on,  103 

salting-out  experiments  on,  104 

salts  of,  10 1 

scheme  for  separation  of,  121 

simple,  93,  95,  96 

Spiegler's  ring  test  for,  103,  440 

synthesis  of,  65,  70 

xanthoproteic  reaction  on,  98 
Proteolysis,  peptic,  141 

tryptic,  I4ij  189 

Proteolytic  enzymes  (see  Proteases,  p.  12) 
Proteose,  63,  93,  95.  ir? 

v.  Aldor's  method  for  detection  of,  443 

biuret  test  on,  119 

coagulation  test  on,  119 

deutero,  93,  95,  119 

differentiation  of,  from  peptone,  119 

experiments  on,  118,  119 

hetero,  94,  119 

in  urine,  430,  442 
test  for,  443 

potassium  ferrocyanide  and  acetic  test  on, 
119 

powder,  preparation  of,  119 

precipitation  of,  by  nitric  acid,  119 
by  picric  acid,  119 
by  potassio-mercuric  iodide,  119 
by  trichloracetic  acid,  119 

primary,  119 

proto,  94,  95,  119 

Schulte's  method  for  detection  of,  443 

secondary,  119 

separation  of,  from  peptones,  119 
Protoproteose,  94,  95,  119 
Proteoses  and  peptones,  94,  95,  118,  119 
separation  of,  119 
tests  on,  119 
Proteose-peptone,  118 
Proteose-peptone,  coagulation  test  on,  119 

experiments  on,  118 

Millon's  reaction  on,  118 

precipitation  of,  by  nitric  acid,  119 

by  picric  acid,  119 
Prothrombin,  259,  260 
Pseudo-globulin,  249 

Psychical  stimulation  of  gastric  secretion,  148 
Ptomaines  and  leucomaines  in  urine,  387,  419 
Ptyalin  (see  Salivary  amylase,  i,  4,  10,  54,  190) 
Purinases,  126,  133 

experiments  on,  133 
Purine  bases,  124,  125,  131,  358,  364,  387,  419, 

533,  607 
formulas  for,  126,  364 

in  urine,  quantitative  determination  of,  533 
tests  on,  131,  132 

content  of  foods,  605 

excretion,  rate  of,  607 

oxidases,  5,  126,  133 
Purines,  amino,  126,  131 

oxy,  126,  131 

Purine-free  and  high  purine  diets,  influence  of,  604 
Pus  casts  in  urinary  sediments,  482,  489 
Pus  cells  in  urinary  sediments,  482,  483 

in  urine,  447 

tests  for,  447,  448 


Putrefaction,  control  of,  by  carbohydrate,  216 

indican  as  an  index  of,  215,  404 
Putrefaction  mixture,  preparation  of  a,  217 
products,  215 

experiments  on,  217 

most  important,  215 

tests  for,  221 
Putrescine,  215 
Pyloric  glands,  137 
Pyrimidine  bases,  124,  125,  127 

experiments  on,  132 

formulas  for,  127 

Pyrocatechol-sulphuric  acid,  386,  404 
a-pyrrolidine-carboxylic  acid  (see  Proline,  pp.  64, 

66,  67,  82,  no,  141,  189) 
Pyuria,  447 

Quadriurate,  478 

Qualitative  analysis  of  the  products  of  salivary 

digestion,  59 

Quantitative  analysis  of  blood,  273 
of  gastric  juice,  150 
of  milk,  341 
of  urine,  496 

Quevenne  lactometer,  determination  of  specific 
gravity  of  milk  by,  341 

Raffinose,  19,  41 

Rancid  fat,  181 

Rats,  white,  experiments  on,  580 

Raw  and  heated  milk  tests,  338 

Reaction  of  the  urine,  378,  424,  499,  613 

Reagents  and  solutions,  627 

Reduced  alkali-hematin,  302 

Reduced  hemoglobin,  300 

Reductases,  337 

Regurgitation,   automatic   regulation   of   gastric 

acidity  by,  149 
Rehfuss  stomach  tube,  cut  of,  151 

use  of,  151,  162 
Reichert's    method    for    crystallization    of    oxy- 

hemoglobin,  269 
Reinsch  test  for  arsenic,  464 

for  mercury,  465 
Remont's  method  for  detection  of  salicylic   acid 

and  salicylates,  341 
Rennin,  gastric,  138,  142,  147,  331,  338 

action  of,  upoh  casein,  142,  147,  331,  338 

experiments  on,  147,  338 

influence  of,  upon  milk,  147,  338 

in  gastric  juice,  absence  of,  142 

nature  of  action  of,  142,  331 

occurrence  of,  142 
Rennin,  pancreatic,  5,  192,  197 

experiments  on,  197 
Rennin-pepsin  controversy,  142 
Resorcinol-HCl  reaction,  34,  462 
Respiration,  chemistry  of,  258 
Respiratory  exchange,  determination  of,  328 
Retention  meal  in  gastric  analysis,  164 
Reticulin,  in 

Reversibility  of  enzyme  action,  8,  56 
Rhamnose,  19,  37 

Rhubarb,  influence  of,  on  color  of  feces,  241 
d-ribose,  in  nucleoprotein,  123 
Ricin,  13,  265 
Rigor  mortis,  357,  358 


670 


INDEX 


Ring  test  for  urobilin,  418 

Roaf 's  method  for  crystallizing  hippuric  acid,  407, 

620 

Robert's  ring  test  for  protein,  103,  440 
reagent,  preparation  of,  103,  440 
Robin's  reaction  for  urorosein,  467 
Rosenheim's  bismuth  test  for  choline,  375 
Rosenheim's  periodide  test  for  choline,  374 
Rosenheim  and  Drummond's  volumetric  methods 

for  sulphates  and  total  sulphur,  566,  567 
Rose's  method  for  determination  of  pepsin,  170 
Rosolic  acid,  use  of,  as  indicator,  156,  161 
Russo's  reaction,  470 
Ruttan  and  Hardisty's  ortho-tolidin  test  for  blood, 

173,  236,  266,  446 

Saccharide  group,  20 
Saccharose  (see  Sucrose,  19,  40) 
Sahli's  desmoid  reaction,  146 

reagent,  167 
Salicylaldehyde  reaction  for  acetone  (Frommer), 

452 
Saliva,  S3 

alkalinity  of,  54 
amount  of,  54 
bacteria  in,  57 
biuret  test  on,  57 
calcium  in,  58 
chlorides  in,  58 
constituents  of,  54 
digestion  of  dry  starch  by,  59 
digestion  of  inulin  by,  59 
digestion  of  starch  paste  by,  55,  58 
dilution  of,  influence  on  digestion,  59 
enzymes  contained  in,  54 
excretion  of  potassium  iodide  in,  60 
inorganic  matter  in,  tests  for,  58 
Millon's  reaction  on,  57 
mucin  from,  preparation  of,  58 
nitrites  in,  test  for,  58 
phosphates  in,  test  for,  58 
potassium  thiocyanate  in,  58 
reaction  of,  54,  57 
secretion  of,  53 
specific  gravity  of,  54,  57 
sulphates  in,  test  for,  58 
tests  on,  57 
thiocyanates  in,  54,  58 
tripeptide-splitting  enzymes  in.  56 
Salivary  amylase,  i,  4,  10,  55,  191 

activity  of,  in  stomach,  56,  191 
inhibition  of  activity  of,  56 
nature  of  action  of,  55,  56 
products  of  action  of,  55 
scheme  showing,  55 
Salivary  digestion,  53 

graphic  representation  of,  55 
influence  of  acids  and  alkalis  on,  55,  60 
dilution  on,  56,  59 
metallic  salts  on,  60 
temperature  on,  59 
Salivary  digestion,  nature  of  action  of  acids  and 

alkalis  on,  60 

qualitative  analysis  of  products  of,  59 
Salivary  digestion  in  stomach,  56,  191 
glands,  S3 

Rockwood  method,  56 
stimuli,  53 


Salkowski-Autenrieth-Barth    method    for    deter- 
mination of  oxalic  acid  in  urine,  562 
Salkowski's  test  for  cholesterol,  213,  374 

for  creatinine,  402 
Salmine,  66,  67,  68,  94,  95 
"Salt-free"  diet,  metabolism  on  a,  609 
Salted  plasma,  preparation  of,  271 
Salting-out  experiments  on  proteins,  104,  121 
Santonin,  influence  of,  on  color  of  feces,  241 
Saponification,  180,  184,  185 
of  bayberry  tallow,  184 
of  lard,  185 
Sarcolactic  acid,  359 

Scallops,  preparation  of  glycogen  from,  366 
Scheme  for  analysis  of  biliary  calculi,  212 
bone  ash,  356 
stomach  contents,  162 
urinary  claculi,  494 
separation  of  carbohydrates,  52 

of  proteins,  121 
Scherer's  coagulation  method   for  determination 

of  albumin  in  urine,  550 
Schiff's  reaction  for  cholesterol,  213,  374 

for  uric  acid,  398 
Schmidt  diet,  composition  of ,  231 
Schmidt's  nuclei  test  for  pancreatic  insufficiency, 

240 

Schmidt's  test  for  hydrobilirubin,  238 
Schulte's   method  for  detection  of  proteose  in 

urine,  443 

Schutz's  law,  statement  of,  9,  169 
Schweitzer's  reagent,  action  of,  on  cellulose,  49 

preparation  of,  48 

Scleroproteins  (see  Albuminoids),  93,  in 
Scombrine,  66,  94  x 
Scombrone,  93,  95 
Scybala,  49,  226 

Secondary  protein  derivatives,  64,  95,  117 
Secondary  proteoses,  119 
Secretin,  188 
Seliwanoff  s  reaction  34,  462 

reagent,  preparation  of,  34,  462 
Senna,  influence  of,  on  color  of  feces,  241 
Separation  of  feces,  importance  of,  in  nutrition 

and  metabolism  experiments,  227,  620 
Serine,64,  66,  68,  72 

crystalline  form  of,  72 
formula  for,  72 

Serum  albumin,  93,  249,  270,  430,  438 
in  urine,  430,  438 

test  for,  439 
Serum,  blood,  249,  270 

milk,  329 

Serum  globulin,  93,  249,  430,  438 
in  urine,  430,  438 
test  for,  442 

Shackell's  method  for  vacuum  desiccation,  504 
Silicates  in  urine,  387,  429 
Silver  lactate  solution,  646 
Silver  reduction  test  for  uric  acid  (Schiff),  398 
Skatole,  215,  216,  217,  222 

tests  for,  222 
Skatole-carbonic  acid,  220,  223 

test  for,  223 
Soap,  salting-out  of,  184 

insoluble,  preparation  of,  185 
Sodium  and  potassium  in  urine,  387,  427,  576 
quantitative  determination  of,  576 


INDEX 


671 


Sodium  alizarin  sulphonate  as  indicator,  156,  157, 

160,  177,  501 

Sodium  alizarin  sulphonate,  preparation  of,  15? 
Sodium  chloride,  crystalline  form,  270 
Sodium  chloride  in  urine,  423,  572»  609 
Sodium  hydroxide  solution,  N/io,  preparation  of, 

497 

Sodium  hypobromite  solution,  preparation  of,  635 
Sodium     nitrite-ferrous    sulphate     reaction     for 

acetoacetic  acid  (Hurtley),  454 
'odium  nitroprusside  test  for  acetone,  452 
odium  sulphide  solution,  preparation  of,  643 
olera's  reaction  for  detection  of  thiocyanate  in 

saliva,  58 

test  paper,  preparation  of,  58 
Dluble  starch,  n,  42,  55 

as  indicator,  168,  289,  543,  557 
5rensen's   formol   titration   method   for   amino 

nitrogen,  523  . 

indicator  method  for  hydrogen  ion  concen- 
tration, 160,  500 

Soxhlet  apparatus  for  extraction  of  fat,  344 
Soxhlet    lactometer,    determination    of    specific 

gravity  of  milk  by,  253 
Specificity  of  enzyme  action,  7 
Spectroscope,  use  of  in  detection  of  blood,  300 
Spermatozoa    in    urinary    sediments,    482,    490 

microscopical  appearance  of  human,  491 
Spiegler's  ring  test  for  protein,  103,  440 

reagent,  preparation  of,  103,  440 
Spiro's  reaction  for  hippuric  acid,  407 
Spongin,  68 
Standard  acid  and  alkali  solutions,  preparation  of, 

496 
ammonium  thiocyanate  solution,  preparation 

of,  627 

creatinine  solution,  632 
iodine  solution,  636 
potassium  permangante,  640 
picramic  acid,  641 

silver  nitrate  solution,  preparation  of,  631 
sodium  alcoholate,  643 
sodium  thiosulphate,  643 
uranium  acetate  solution,  preparation  of,  645 
uric  acid  solution,  646 
Starch,  20,  42 

action  of  alcohol  on  iodide  of,  44 
action  of  alkali  on  iodide  of,  44 

heat  on  iodide  of,  44 
raw,   digestion   of,   by  pancreatic   amylase, 

191,  195 

raw,  digestion  of,  by  salivary  amylase,    59 
experiments  on,  42 
hyperglycemia  produced  by,  598 
iodine  test  for,  44 

microscopical  characteristics  of,  42,  43 
examination  of,  44 
potato,  preparation  of,  42 
soluble,  ii,  42,  55 

soluble  starch  as  indicator,  168,  289,  543,  557 
solubility  of,  42,  44 
various  forms  of,  43 
Starch  group,  20 

Starch  paste,  action  of  tannic  acid  on,  44 
diffusibility  of,  44 
digestion  of,  by  pancreatic  amylase,  191, 

194 
by  salivary  amylase,  10,  55,  58 


Starch  paste,  Fehling's  test  on,  44 
hydrolysis  of,  44 
iodic  acid  paper,  58 
preparation  of,  44 
Steapsin  (see  Pancreatic  lipase,  5.  13,  181,  191, 

196) 

Stearic  acid,  180,  371 
Stearin,  180,  181,  329 
Stehle's  gasometric  method  for  urea,  518 
Stellar  phosphate,  340,  477 
Stercobilin,  225 
Stokes'  reagent,  action  of,  301 

preparation  of,  301 

Stomach  contents,  lactic  acid  in,  tests  for,  172 
examination  of,  162 
peptide-splitting  enzyme  in,  141,  202 
removal  of,  164 
tube,  Rehfuss,  150,  151 
Stomach,  motor  and  functional  activities  of,  146, 

162 

Stone-cystine,  76 
Sturine,  66,  67,  93 
Sublingual     glands,     characteristics     of     saliva 

secreted  by,  53  - 
Submaxillary    glands,     characteristics    of   saliva 

secreted  by,  53 
Substrate,  3 
Succinic  acid,  217 
Sucrase,  4,  14,  198,  202 

experiments  on,  14,  202 
vegetable,  14 
Sucrose,  19,  40 

experiments  on,  41 
inversion  of,  41 
structure  of,  41 

Sucrose-HsSO*  test  (Pettenkofer),  211,  449 
Sugar  (see  Glucose  and  Sucrose) 
Sulphanilic  acid,  469 
Sulphates  in  saliva,  test  for,  58 
Sulphates  in  urine,  387,  421,  562 
ethereal,  402,  564 

quantitative  determination  of,  564 
experiments  on,  404,  422 
inorganic,  421,  564 

quantitative  determination  of,  564 
total,  quantitative  determination  of,  562, 

S6s 
Sulphocyanides  (see  Thiocyanates,   54,  58,  386, 

409) 

Sulphur  in  protein,  62,  107 
acid,  107 

in     urine,     gravimetric     determination     of, 
562 

volumetric  determination  of,  566 
lead  blackening,  107,  423 
loosely  combined,  107,  421 
mercaptan,  107,  421 
neutral,  107,  421 
oxidized,  107,  421 
"partition,"  in  urine,  610 
tests  for,  107 
unoxidized,  107,  421 
Sulphuric  acid  test  (Piria),  85 
Surface  tension  test  for  bile  acids   (Hay),  212, 

449 

Suspension  of  manganese  dioxide,  645 
Synthesis  of  hippuric  acid,  619 

demonstration  of,  619 


672 


INDEX 


Tallow  bayberry,  saponification  of,  185 
Tannic  acid,  influence  of,  on  dextrin,  47 

on  starch,  44 

precipitation  test  for  nucleoprotein, 

(Ott),  444 
Tannin  test   for  carbon   monoxide  hemoglobin, 

302 

Tartar,  formation  of,  54 
Taurine,  207,  213,  358,  364,  386,  409 
derivatives,  386,  409 
formula  for,  207,  364 
microscopical  appearance,  214 
preparation  of,  213 
Taurocholic  acid,  207 

group,  207 

Taylor  and  Hulton's  report  on  sugar  in  urine,  2 1 
Teeth,  348,  356 

composition  of,  356 
Teichmann's     crystals,     form     of     (see     Hemin 

crystals,  p.  267) 
test,  267,  269,  446 
Tendomucoid,  94,  112,  349 
biuret  test  on,  350 
chemical  composition  of,  112 
hydrolysis  of,  350 

loosely  combined  sulphur  in,  test  for,  350 
preparation  of,  350 
solubility  of,  350 
Test  meals,  162,  164 

Ewald,  162,  164 
retention,  162,  164 
water,  162,  164 
Tetrapeptides,  65,  95 
Tetramethylene-diamine,  217 
Tetranucleotide,  124 

Thiocyanates  in  saliva,  significance  of,  54 
ferric  chloride  test  for,  58 
Solera's  reaction  for,  58 
Thiocyanates  in  urine,  386,  409 
Thiophene  reaction,  173 
Thrombin,  250,  259,  260 
Thromboplastin,  260 
Thy  mine  in  nucleic  acids,  124,  125,  132 
Thymol,  formula  for,  384 

interference  in  Heller's  ring  test,  439 

determination  of  sugar,  acetone  bodies, 
phosphates  and  magnesium  in  urine, 
384 

interference  of,  in  Lieben's  acetone  test,  452 
use  of,  as  preservative,  384 
Thymolphthalein,  use  of,  as  indicator,  161 
Thymus  histone,  93 

nucleic  acid,  123,  130 

preparation  of,  130 
tests  on,  131 

Time  relations  of  protein  metabolism,  602 
Tincture  of  iodine,  preparation  of,  645 
Tisdall's  modification  of  Folin-Denis  method  for 

phenols  in  urine,  561 

Tissue,  adipose,  experiments  on,  179,  356      '   . 
connective,  349,  350 
white  fibrous,  349 

composition  of,  349 
experiments  on,  350 
"yellow  elastic,  351 

composition  of,  352 
experiments  on,  352 
epithelial,  348 


Tissue,  epithelial,  experiments  on,  349 
muscular,  357 

experiments  on,  364 
nervous,  370 

experiments  on,  373 
.osseous,  354 

experiments  on,  355 

Tissue  debris  in  urinary  sediments,  482,  490 
Titanium  tetrachloride  as  cellulose  solvent,  49 
o-Tolidin  test  for  blood,  173,  236,  266,  446 
Tollen's  reaction  for  conjugate  glycuronates,  4 
arabinose,  37 
galactose,  35,  461 
pentoses  in  urine,  458 
Topfer's    method    for    quantitative    analysis 

gastric  juice,  176 
Topfer's  reagent,  as  indicator,  156,  157,  166,  17 

177 

preparation  of,  177 
Total  nitrogen,  of  urine,  quantitative  determina 

tion  of,  504 
Total  solids,  of  milk,  quantitative  determination 

of,  344 
of  urine,  quantitative  determination  of, 

504 

Total  sulphur  of  urine,  quantitative  determina- 
tion of,  562,  566 
phosphorus    of    urine,    quantitative    deter 

mination  of,  57O 
Trichloracetic  acid,  precipitation  of  protein  by, 

102,  119 

Tricresol-peroxidase  reaction  (Kastle),  338 
Triketohydrindene  hydrate  (ninhydrin)  reaction, 

100 
Trimethyl-oxyethyl-ammonium    hydroxide     (see 

Choline,  215,  371,  374) 
Trioses,  19 
Tripeptides,  65,  95 

Triple  phosphate,  389,  390,  475,  493.  520 
crystalline  form  of,  426 
formation  of,  426 
Trisaccharides,  19,  41 
Trommer's  test,  24,  433 
Tropaeolin  O,  use  of ,  as  indicator,  161 

preparation  of,  161 
Tropaeolin  OO,  use  of,  as  indicator,  156,  157,  158, 

160,  161 

preparation  of,  158,  160 
Tropseolin  OOO,  use  of,  as  indicator,  161 

preparation  of,  161 
Trypsin  (see  also  Pancreatic  protease,  5,  12,  189, 

190) 

action  of,  upon  proteins,  65,  189,  192 
experiments  on,  192-3 
influence      of     alkalis     and     mineral     acids 

upon,  193 

in  stomach,  153,  154,  i?i 
determination  of,  171 
nature  of,  189 

quantitative  determination  of,  171,  194 
Trypsinogen,  6,  189,  190 

activation  of,  6,  189,  199,  200 
Tryptic  digestion,  65,  189 

influence  of  bile  on,  194 

most  favorable  reaction  for,  193 

temperature  for,  193 
products  of,  65,  189,  192 
Tryptic  proteolysis,  141,  189 


INDEX 


673 


Tryptophane,  64,  66,  67,  76,  98,  189,  192 

bromine  water  test  for,  192 

formula  for,  76 

group  in  the  protein  molecule,  98 

Hopkins-Cole  reaction  for,  98 

mercury  compound  of,  preparation  of,   192 

occurrence  of,  as  a  decomposition  product  of 
protein,  64,  66,  67,  76 

occurrence   of,   as   an   end-product   of  pan- 
creatic digestion,  189,  192 

Tuberculosis,    urochromogen    reaction    for,    468 
Tussah  silk  fibroin,  67 
Tyrosinase,  5 
Tyrosine,  5,  64,  66,  68,  73,  85,  97,  189,  475,   480 

crystalline  form  of,  75 

experiments  on,  85 

formula  for,  76 

Hoffmann's  reaction  for,  85 

in  urinary  sediments,  475,  480 

microscopical  examination  of,  85 

Morner's  test  for,  85 

occurrence  of,. 64,  66,  68,  189 

Piria's  test  for,  85 

salts  of,  76 

separation  of,  from  leucine,  84' 

solubility  of,  85 

sublimation  of,  85 
Tyrosine-sulphuric  acid,  85 

v.  Udransky's  test  for  bile  acids,  211,  449 
Uffelmann's  reagent,  preparation  of,  173,  645 

reaction  for  lactic  acid,  173 
Unknown  substances  in  urine,  469 
Unorganized  ferments,  i 

sediments  in  urine,  475 
Unsaturated  acids,  180 
Uranium  acetate   method  for  determination   of 

total  phosphates  in  urine,  568 
Uracil,  124,  127,  132 

Wheeler-Johnson  reaction  for,  132 
Urate,  ammonium,  crystalline  form  of,  Plate  VI, 

opposite  p.  479 

sodium  crystalline  form  of,  479 
Urates  in  urinary  sediments,  475,  478     • 
Urea,  250,  251,  273,  278,  358,  386,  388,  389,  514 
crystalline  form  of,  389 
decomposition  of,  by  sodium  hypobromite, 

391,  393 

decomposition  of,  by  urease,  391,  393 
excretion  of,  389,  391 
experiments  on,  392 
formation  of,  390 
formula  for,  389 
isolation  of,  from  the  urine,  392 
melting-point  of,  392 
quantitative  determination  of,  in'blood,  278 

in  urine,  514 
Urea  nitrate,  391,  393 

crystalline  form  of,  391 
formula  for,  391 
c.jcalate,  391,  393 

crystalline  form  of,  393 
formula  for,  391 
Urease,  4,  278,  391,  514,  646 

decomposition  of  urea  by,  391,  393,  514 
.    preparation  of,  515,  646 
quantitative  determination  of  urea  by,  278, 
514 
43 


Uremia,  blood  in,  273,  274 

Urethral  filaments  in  urinary  sediments,  482,  490 
Uric  acid,  26,  126,  132,  136,  251,  273,  281,  358, 
386,  394,  434,  475,  477.  493,  53O,  605. 
606 

calculi,     493 

crystalline  form  of,  pure,  397 
endogenous,  395,  604,  606 
exogenous,  395,  604,  606 
experiments  on,  397 
formula  for,  394 
Ganassini's  test,  398 
in  blood,  250,  251,  273,  281 
in  gout,  273,  283,  396,  604,  607 
in  leukaemia,  396 
in  urinary  sediments,  475,  479 

crystalline  form  of,  Plate  V,  oppo- 
site p.  397.  478 

isolation  of,  from  the  urine,  397 
metabolism,  604-607 
murexide  test  for,  397 
origin  of,  395 
quantitative  determination  of,  in  blood, 

Folin-Wu   method,    281 
in  urine,  microchemical  color - 

imetric  method,  530 
Folin-Shaffer  method,  532 
Kruger-Schmidt   method, 

533 

reagent,  646 

reducing  power  of,  26,  396,  398,  434 
Schiff 's  reaction  for,  398 
standard,  646 
Uricase,  5,  126,  136 

experiments  on,  136 
Uricolytic  enzymes,  3,  5,  126,  136 

experiments  on,  136 
Urinary  calculi,  492 

calcium  carbonate  in,  493 
cholesterol  in,  495 
compound,  492 
cysfrine  in,  493 
fibrin  in,  495 
indigo  in,  495 
oxalate  in,  493 
phosphates  in,  493 
scheme  for  chemical  analysis  of,  494 
simple,  492 

uric  acid  and  urates  in,  493 
urostealiths  in,  495 
xanthine  in,  493 

Urinary  concrements  (see  Urinary  calculi,  p.  492) 
Urinary  sediments,  474 

ammonium    magnesium    phosphate    in, 

475 

animal  parasites  in,  482,  491 
calcium  carbonate  in,  475,  476 
oxalate  in,  475 
phosphate  in,  475,  477 
sulphate  in,  475,  477 
casts  in,  482,  484-489 
cholesterol  in,  475,  480 
collection  of,  474 
cylindroids  in,  482,  489 
cystine  in,  475,  479 
epithelial  cells  in,  482 
erythrocytes  in,  482,  489 
fibrin  in,  482,  491 


674 


INDEX 


Urinary  sediments,  foreign  substances  in,  482,  491 

hemaitodin  and  bilirubin  in,  475,  481 

hippuric  acid  in,  415,  480 

indigo  in,  475,  481 

leucine  and  tyrosine  in,  475,  480 

magnesium  phosphate  in,  475,  481 

melanin  in,  475,  482 

micro-organisms  in,  482,  491 

organized,  475,  482 

pus  cells  in,  482,  483 

spermatozoa  in,  482,  490 

tissue  debris  in,  482,  490 

unorganized,  475 

urates  in,  475,  478 

urethral  filaments  in,  482,  490 

uric  acid  in,  475,  477 

xanthine  in,  475,  481 
Urination,  frequency  of,  378 
Urine,  376 

acetoacetic  acid  in,  430,  453,  552 

acetone  in,  430,  450,  552,  557 

acidity  of,  387,  424,  499,  500,  613,  615 

acid  fermentation  of,  380 

albumin  in,  430,  438 

alkaline  fermentation  of,  379,  426 

allantoin  in,  386,  409,  535 

amino-acids  in,  386,  411,  523 

ammonia  in,  387,  420,  519,  608 

aromatic  oxyacids  in,  386,  411 

arsenic  in,  462 

Bence-Jones1  protein  in,  438,  444 

benzoic  acid  in,  386,  405,  412,  616,  619 

bile  in,  430,  448 

blood  in,  430,  445 

calcium  in,  387,  423.  427,  574 

carbonates  in,  387,  4.28 

chlorides  in,  387,  423,  572 

collection  of,  384,  598 

collection  and  preservation  of,  in  metabolism 

tests,  384,  598 
color  of,  376 

complete  analysis  of,  388,  598 
conjugate  glycuronates  in,  430,  434,  456 
creatine  in,  360,  363,  $67,  386,  401,  430,  529 
creatinine  in,  387,  398,  526,  607 
dextrose  in  (see  Glucose,  414,  430,  431,  438) 
diacetic  acid  in  (see  Acetoaceticacid  ,430,  453, 

552) 

electrical  conductivity  of,  383 
enzymes  in,  387,  415 

ethereal  sulphuric  acid  in,  386,  402,  564,  568 
fat  in,  430,  459,  482,  486 
fluorides  in,  387,  429 
freezing-point  of,  382 
fructose   in,  430,  461 
galactose  in,  430,  460 
general  characteristics  of,  376 
globulin  in,  430,  441 
glucose  in,  414,  430,  431,  538 

Folin's  test  for,  in  normal,  414 
Haser's  coefficient  for  solids  in,  381,  504 
hematoporphyrin  in,  430,  459 
hippuric  acid  in,  386,  405,  414,  480,  537  619 
hydrogen  ion  concentration  of,  378,  500,  613 

615,  616 
as  influenced  by  diet,  613  ' 

by  acid  and   alkali,   615, 
616 


Urine,  hydrogen  peroxide  in,  387,  429 

j8-hydroxybutyric    acid    in,    4^0.    450,    455, 

554 

indican  in,  215,  558 
inorganic  physiological  constituents  of,  387 

420 

inositol  in,  430,  465 
iron  in,  387,  429,  577 
lactose  in  430,  459 
laiose  in,  430,  466 
leucomaines  in,  387,  419 
levulose  in  (see  Fructose,  430,  461) 
Long's  coefficient  for  solids  in,  381,  504 
magnesium  in,  387,  427,  574 
melanin  in,  430,  466 
mercury  in,  464 
neutral  sulphur  compounds  in,  386,  409,  562, 

611 

nitrates  in,  387,  429 

nitrogen,  total,  determination  of,  in,  504-514 
nucleoprotein  in,  386,  414,  430,  444 
odor  of,  378 

organic  physiological  constituents  of,  386 
oxalic  acid  in,  386,  408,  562 
oxaluric  acid  in,  386,  414 
/3-oxybutyric   acid   in    (see    Hydroxybutyric 

acid,  430,  450,  455,  554 
paralactic  acid  in,  387,  415 
pathological  constituents  of,  430 
pentoses  in,  430,  457 
peptone  in,  430,  442 
phenaceturic  acid  in,  387,  416 
phenols  in,  403,  559,  561 
phosphates  in,  387,  424,  568 
phosphorized  compounds  in,  387,  416 
physiological  constituents  of  386 
pigments  of,  376,  387,  415,  417 
potassium  in,  387,  427,  576 
proteins  in,  430,  438,  550 
proteoses  in,  430,  438,  442 
ptomaines  in,  387,  419 
purine  bases  in,  387,  419,  533,  607 
pus  in,  447 

quantitative  analysis  of,  496-578 
reaction  of,  378,  424,  499,  613 
as  influenced  by  diet,  613 

by  acids  and  alkalies,  615 
silicates  in,  387,  429 
sodium  in,  387,  427,  576 
solids  of,  381,  504 
specific  gravity  of,  380 
sulphates  in,  387,  421,  562 
sulphur  in,  562 

total  nitrogen  determination  in,  504 
transparency  of,  377 
triple  phosphate  in,  426,  475 
unknown  substances  in,  430,  469 
urea  in,  386,  388,  389,  510,  SU-SiQ 
urobilin  in,  417 
urocanic  acid  in,  416 
uric  acid  in,  386,   394,  475,  477,  493. 
urinod  in,  378 
urochrome  in,  417,  4°7 
uroerythrin,  419 
urorosein  in,  430,  467 
volatile  fatty  acids  in,  387,  415 
volume  of,  376 
Urinod,  378 


' 


INDEX 


Urobilin,  376,  387.  417 

tests  for,  418 
Urobilinogen,  417 
Urocanic  acid,  387,  416 
Urochrome,  376,  387,  4*7.  436,  467 
Urochromogen,  430,  467 

reaction  (Weisz)  for  tuberculosis,  468 
Uroerythrin,  376,  387,  416,  436 
Uroferric  acid,  386,  409,  469 
Uroleucic  acid,  386 
Urorosein,  430,  467 

reaction,  467 

tests  for,  467 

Valine,  64,  66,  68,  77 

Van  Slyke's  apparatus  for  alkali  reserve,  312 

for  amino  nitrogen,  87 
Van  Slyke's  method  for  determination  of  total 

amino-acid  nitrogen  in  urine,  526 
.  in  protein  hydrolysis^  87 
acetone  bodies  in  urine,  j  5  2^ 

Van  Slyke  and  Cullen's  method  for  urea  in  blood, 
286 

for  carbon  dioxide  capacity 

of  plasma,  311     • 
for  urea  in  urine,  514 
Van  Slyke  and  Palmer  method  for  organic  acids 

in  urine,  500 

Van  Slyke,  Stillman,  and  Cullen,  plasma  bicar- 
bonate titration,  318 
Vegetable  amylase,  4,  1 1 
lipase,  5,  13 
protease,  13 
sucrase,  198,  202 

Vegetable  globulins,  93,  95,  107,  108 
Vegetable  gums,  20 
V  ith  lactometer.determination  of  specific  gravity 

of  milk  by,  341 
Viscosity  test,  58 
Vitamine,  329,  336,  580 
Vitamine,  influence  of  deficiency  of,  580 

influence  of  deficiency  of  fat-soluble  A,    585 
water-soluble  B,  582 

C,  585 

\  itellin,  94,  95 

Volatile  fatty  acids,  215,  218,  387,  415 
Volhard-Arnold    method    for    determination,  of 

chlorides,  572 
Volhard-Harvey    method    for    determination    of 

chlorides,  573 
Volume  of  the  urine,  376 

Water  at  meals,  influence  of.  137.  188,  420,  607 

softened,  56 
Water  test  meal,  164 
Water,  influence  of  on  metabolism,  607 
Water  deficiency,  influence  of,  597 
Water-soluble  "B,"  influence  of  on  growth,  581 

occurrence  of,  581 
Water-soluble  "C,"  influence  of,  581 

occurrence  of,  581 
Wax  myrtle,  184 

Waxy  casts  in  urinary  sediments,  482,  487 
Weinland,  formation  of  fat  from  protein,  182 
Weisz's  urochromogen  reaction  for  tuberculosis, 

467 
Welker's    modified    method    for    purine    bases. 

535 


Welker   and    Marsh   method   for   deproteinizi  ij? 

milk,  347 
Welker   and    Tracy    method   for   deprotcinizir  g 

urine,  506 

Weyl's  test  for  creatinine,  402 
Wheeler-  Johnson  reaction  for  uracil  and  cytosin<% 

132 
White  fibrous  connective  tissue,  349 

experiments  on,  350 

Whitehorn  method  for  chlorides  in  blood,    285 
White  rats,  experiments  on,  580 
Wiechowski-Handovsky     method    for    dett     - '  • 

nation  of  allantoin  in  urine,  535 
Wilkinson  and  Peters'  test,  338 
Wirsing's  test  for  urobilin,  418 
Witchs'  milk,  335 

Wohlgemuths'    method   for    quantitative    deter- 
mination of  amylolytic  aqtivity,   1^5 
Author's  modification  of,  242 
Wolter's   method  for   determination  of   iron    in 

urine,  577 

Xanthine,  125,  126,  131,  358,  362,  364,  368,  4:9 

bases  (see  Purine  Bases,  pr      "".  364,  419) 

crystalline  form  of  3^2 

formula  for,  126,  364 

in  urinary  sediments,  475,  481 

isolation  of,  from  meat  extract,  368 

silver  nitrate,  369 

crystalline  form  of,  369 
test,  368 

tests  for,  131 

Weidel's  reaction  for,  131 
Xanthophylls,  337 
Xanthoproteic  reaction  ,98 
Xanthinoxidase,  5 
d-xyloketose,  458 
Xylose,  20,  37,  458 

orcinol  reaction  on,  37 

phenylhydrazine  reaction  on,  37 

Tollens'  reaction  on,  37 

Yeast,  eneymes  of,  2 

fermentation  by,  29,  30 
growth-promoting  .substance  in,  581 
influence  on  growth  581 
nucleoprotein  of.  127 

preparation  of,  127  5& 
tests  on,  128 
nucleic  acid  of,  124,  129 
formula  for,  124 
preparation  of,  129 
tests  on,  129 

water-soluble  vitamine  in,  581 
Yellow  elastic  connective  tissue,  351 
composition  of »  352 
experiments  on  ,352 

Youngburg's    modification    of    Van    v£yke    and 
Cullen's  method  for  urea  in  urine,  516 

Zein,  66,  68,  93,  95,  no 

decomposition  of,  66,  68 
Zeller's  test  for  melanin,  466 
Zikel  pektoscope,  382 
Zymase,  classification  of,  4 

preparation  of,  2 
Zymo-exciter,  7 
Zymogen,  6,  189 


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